Java

JavaTM Debug Wire Protocol
Specification Details

 JDWP

  • VirtualMachine Command Set (1)
  • ReferenceType Command Set (2)
  • ClassType Command Set (3)
  • ArrayType Command Set (4)
  • InterfaceType Command Set (5)
  • Method Command Set (6)
  • Field Command Set (8)
  • ObjectReference Command Set (9)
  • StringReference Command Set (10)
  • ThreadReference Command Set (11)
  • ThreadGroupReference Command Set (12)
  • ArrayReference Command Set (13)
  • ClassLoaderReference Command Set (14)
  • EventRequest Command Set (15)
  • StackFrame Command Set (16)
  • ClassObjectReference Command Set (17)
  • Event Command Set (64)
  • Error Constants
  • EventKind Constants
  • ThreadStatus Constants
  • SuspendStatus Constants
  • ClassStatus Constants
  • TypeTag Constants
  • Tag Constants
  • StepDepth Constants
  • StepSize Constants
  • SuspendPolicy Constants
  • InvokeOptions Constants

    VirtualMachine Command Set (1)

    Version Command (1)
    Returns the JDWP version implemented by the target VM. The version string format is implementation dependent.
    Out Data
    (None)
    Reply Data
    stringdescriptionText information on the VM version 
    intjdwpMajorMajor JDWP Version number 
    intjdwpMinorMinor JDWP Version number 
    stringvmVersionTarget VM JRE version, as in the java.version property 
    stringvmNameTarget VM name, as in the java.vm.name property 
    Error Data
    VM_DEADThe virtual machine is not running. 
    ClassesBySignature Command (2)
    Returns reference types for all the classes loaded by the target VM which match the given signature. Multple reference types will be returned if two or more class loaders have loaded a class of the same name. The search is confined to loaded classes only; no attempt is made to load a class of the given signature.
    Out Data
    stringsignatureJNI signature of the class to find (for example, "Ljava/lang/String;").  
    Reply Data
    intclassesNumber of reference types that follow. 
    Repeated classes times:
    byterefTypeTagKind of following reference type.  
    referenceTypeIDtypeIDMatching loaded reference type 
    intstatusThe current class status.  
    Error Data
    VM_DEADThe virtual machine is not running. 
    AllClasses Command (3)
    Returns reference types for all classes currently loaded by the target VM.
    Out Data
    (None)
    Reply Data
    intclassesNumber of reference types that follow. 
    Repeated classes times:
    byterefTypeTagKind of following reference type.  
    referenceTypeIDtypeIDLoaded reference type 
    stringsignatureThe JNI signature of the loaded reference type 
    intstatusThe current class status.  
    Error Data
    VM_DEADThe virtual machine is not running. 
    AllThreads Command (4)
    Returns all threads currently running in the target VM . The returned list contains threads created through java.lang.Thread, all native threads attached to the target VM through JNI, and system threads created by the target VM. Threads that have not yet been started and threads that have completed their execution are not included in the returned list.
    Out Data
    (None)
    Reply Data
    intthreadsNumber of threads that follow. 
    Repeated threads times:
    threadIDthreadA running thread 
    Error Data
    VM_DEADThe virtual machine is not running. 
    TopLevelThreadGroups Command (5)
    Returns all thread groups that do not have a parent. This command may be used as the first step in building a tree (or trees) of the existing thread groups.
    Out Data
    (None)
    Reply Data
    intgroupsNumber of thread groups that follow. 
    Repeated groups times:
    threadGroupIDgroupA top level thread group 
    Error Data
    VM_DEADThe virtual machine is not running. 
    Dispose Command (6)
    Invalidates this virtual machine mirror. The communication channel to the target VM is closed, and the target VM prepares to accept another subsequent connection from this debugger or another debugger, including the following tasks: Any current method invocations executing in the target VM are continued after the disconnection. Upon completion of any such method invocation, the invoking thread continues from the location where it was originally stopped.

    Resources originating in this VirtualMachine (ObjectReferences, ReferenceTypes, etc.) will become invalid.

    Out Data
    (None)
    Reply Data
    (None)
    Error Data
    (None)
    IDSizes Command (7)
    Returns the sizes of variably-sized data types in the target VM.The returned values indicate the number of bytes used by the identifiers in command and reply packets.
    Out Data
    (None)
    Reply Data
    intfieldIDSizefieldID size in bytes  
    intmethodIDSizemethodID size in bytes  
    intobjectIDSizeobjectID size in bytes  
    intreferenceTypeIDSizereferenceTypeID size in bytes  
    intframeIDSizeframeID size in bytes  
    Error Data
    VM_DEADThe virtual machine is not running. 
    Suspend Command (8)
    Suspends the execution of the application running in the target VM. All Java threads currently running will be suspended.

    Unlike java.lang.Thread.suspend, suspends of both the virtual machine and individual threads are counted. Before a thread will run again, it must be resumed through the VM-level resume command or the thread-level resume command the same number of times it has been suspended.

    Out Data
    (None)
    Reply Data
    (None)
    Error Data
    VM_DEADThe virtual machine is not running. 
    Resume Command (9)
    Resumes execution of the application after the suspend command or an event has stopped it. Suspensions of the Virtual Machine and individual threads are counted. If a particular thread is suspended n times, it must resumed n times before it will continue.
    Out Data
    (None)
    Reply Data
    (None)
    Error Data
    (None)
    Exit Command (10)
    Terminates the target VM with the given exit code. On some platforms, the exit code might be truncated, for example, to the low order 8 bits. All ids previously returned from the target VM become invalid. Threads running in the VM are abruptly terminated. A thread death exception is not thrown and finally blocks are not run.
    Out Data
    intexitCodethe exit code 
    Reply Data
    (None)
    Error Data
    (None)
    CreateString Command (11)
    Creates a new string object in the target VM and returns its id.
    Out Data
    stringutfUTF-8 characters to use in the created string.  
    Reply Data
    stringIDstringObjectCreated string (instance of java.lang.String)  
    Error Data
    VM_DEADThe virtual machine is not running. 
    Capabilities Command (12)
    Retrieve this VM's capabilities. The capabilities are returned as booleans, each indicating the presence or absence of a capability. The commands associated with each capability will return the NOT_IMPLEMENTED error if the cabability is not available.
    Out Data
    (None)
    Reply Data
    booleancanWatchFieldModificationCan the VM watch field modification, and therefore can it send the Modification Watchpoint Event? 
    booleancanWatchFieldAccessCan the VM watch field access, and therefore can it send the Access Watchpoint Event? 
    booleancanGetBytecodesCan the VM get the bytecodes of a given method?  
    booleancanGetSyntheticAttributeCan the VM determine whether a field or method is synthetic? (that is, can the VM determine if the method or the field was invented by the compiler?)  
    booleancanGetOwnedMonitorInfoCan the VM get the owned monitors infornation for a thread? 
    booleancanGetCurrentContendedMonitorCan the VM get the current contended monitor of a thread? 
    booleancanGetMonitorInfoCan the VM get the monitor information for a given object?  
    Error Data
    VM_DEADThe virtual machine is not running. 
    ClassPaths Command (13)
    Retrieve the classpath and bootclasspath of the target VM. If the classpath is not defined, returns an empty list. If the bootclasspath is not defined returns an empty list.
    Out Data
    (None)
    Reply Data
    stringbaseDirBase directory used to resolve relative paths in either of the following lists. 
    intclasspathsNumber of paths in classpath. 
    Repeated classpaths times:
    stringpathOne component of classpath 
    intbootclasspathsNumber of paths in bootclasspath. 
    Repeated bootclasspaths times:
    stringpathOne component of bootclasspath 
    Error Data
    VM_DEADThe virtual machine is not running. 
    DisposeObjects Command (14)
    Releases a list of object IDs. For each object in the list, the following applies. The count of references held by the back-end (the reference count) will be decremented by refCnt. If thereafter the reference count is less than or equal to zero, the ID is freed. Any back-end resources associated with the freed ID may be freed, and if garbage collection was disabled for the object, it will be re-enabled. The sender of this command promises that no further commands will be sent referencing a freed ID.

    Use of this command is not required. If it is not sent, resources associated with each ID will be freed by the back-end at some time after the corresponding object is garbage collected. It is most useful to use this command to reduce the load on the back-end if a very large number of objects has been retrieved from the back-end (a large array, for example) but may not be garbage collected any time soon.

    IDs may be re-used by the back-end after they have been freed with this command.This description assumes reference counting, a back-end may use any implementation which operates equivalently.

    Out Data
    intrequestsNumber of object dispose requests that follow 
    Repeated requests times:
    objectIDobjectThe object ID 
    intrefCntThe number of times this object ID has been part of a packet received from the back-end. An accurate count prevents the object ID from being freed on the back-end if it is part of an incoming packet, not yet handled by the front-end. 
    Reply Data
    (None)
    Error Data
    (None)
    HoldEvents Command (15)
    Tells the target VM to stop sending events. Events are not discarded; they are held until a subsequent ReleaseEvents command is sent. This command is useful to control the number of events sent to the debugger VM in situations where very large numbers of events are generated. While events are held by the debugger back-end, application execution may be frozen by the debugger back-end to prevent buffer overflows on the back end. Responses to commands are never held and are not affected by this command. If events are already being held, this command is ignored.
    Out Data
    (None)
    Reply Data
    (None)
    Error Data
    (None)
    ReleaseEvents Command (16)
    Tells the target VM to continue sending events. This command is used to restore normal activity after a HoldEvents command. If there is no current HoldEvents command in effect, this command is ignored.
    Out Data
    (None)
    Reply Data
    (None)
    Error Data
    (None)
    CapabilitiesNew Command (17)
    Retrieve all of this VM's capabilities. The capabilities are returned as booleans, each indicating the presence or absence of a capability. The commands associated with each capability will return the NOT_IMPLEMENTED error if the cabability is not available.Since JDWP version 1.4.
    Out Data
    (None)
    Reply Data
    booleancanWatchFieldModificationCan the VM watch field modification, and therefore can it send the Modification Watchpoint Event? 
    booleancanWatchFieldAccessCan the VM watch field access, and therefore can it send the Access Watchpoint Event? 
    booleancanGetBytecodesCan the VM get the bytecodes of a given method?  
    booleancanGetSyntheticAttributeCan the VM determine whether a field or method is synthetic? (that is, can the VM determine if the method or the field was invented by the compiler?)  
    booleancanGetOwnedMonitorInfoCan the VM get the owned monitors infornation for a thread? 
    booleancanGetCurrentContendedMonitorCan the VM get the current contended monitor of a thread? 
    booleancanGetMonitorInfoCan the VM get the monitor information for a given object?  
    booleancanRedefineClassesCan the VM redefine classes? 
    booleancanAddMethodCan the VM add methods when redefining classes? 
    booleancanUnrestrictedlyRedefineClassesCan the VM redefine classesin arbitrary ways? 
    booleancanPopFramesCan the VM pop stack frames? 
    booleancanUseInstanceFiltersCan the VM filter events by specific object? 
    booleancanGetSourceDebugExtensionCan the VM get the source debug extension? 
    booleancanRequestVMDeathEventCan the VM request VM death events? 
    booleancanSetDefaultStratumCan the VM set a default stratum? 
    booleanreserved16Reserved for future capability 
    booleanreserved17Reserved for future capability 
    booleanreserved18Reserved for future capability 
    booleanreserved19Reserved for future capability 
    booleanreserved20Reserved for future capability 
    booleanreserved21Reserved for future capability 
    booleanreserved22Reserved for future capability 
    booleanreserved23Reserved for future capability 
    booleanreserved24Reserved for future capability 
    booleanreserved25Reserved for future capability 
    booleanreserved26Reserved for future capability 
    booleanreserved27Reserved for future capability 
    booleanreserved28Reserved for future capability 
    booleanreserved29Reserved for future capability 
    booleanreserved30Reserved for future capability 
    booleanreserved31Reserved for future capability 
    booleanreserved32Reserved for future capability 
    Error Data
    VM_DEADThe virtual machine is not running. 
    RedefineClasses Command (18)
    Installs new class definitions.
    Out Data
    intclassesNumber of reference types that follow. 
    Repeated classes times:
    referenceTypeIDrefTypeThe reference type. 
    intclassfile 
    Repeated classfile times:
    byteclassbytebyte in JVM class file format. 
    Reply Data
    (None)
    Error Data
    INVALID_CLASSOne of the refType is not the ID of a reference type. 
    INVALID_OBJECTOne of the refType is not a known ID. 
    UNSUPPORTED_VERSIONA class file has a version number not supported by this VM. 
    INVALID_CLASS_FORMATThe virtual machine attempted to read a class file and determined that the file is malformed or otherwise cannot be interpreted as a class file. 
    CIRCULAR_CLASS_DEFINITIONA circularity has been detected while initializing a class. 
    FAILS_VERIFICATIONThe verifier detected that a class file, though well formed, contained some sort of internal inconsistency or security problem. 
    NAMES_DONT_MATCHThe class name defined in the new class file is different from the name in the old class object. 
    NOT_IMPLEMENTEDNo aspect of this functionality is implemented (CapabilitiesNew.canRedefineClasses is false) 
    ADD_METHOD_NOT_IMPLEMENTEDAdding methods has not been implemented. 
    SCHEMA_CHANGE_NOT_IMPLEMENTEDSchema change has not been implemented. 
    HIERARCHY_CHANGE_NOT_IMPLEMENTEDA direct superclass is different for the new class version, or the set of directly implemented interfaces is different and canUnrestrictedlyRedefineClasses is false. 
    DELETE_METHOD_NOT_IMPLEMENTEDThe new class version does not declare a method declared in the old class version and canUnrestrictedlyRedefineClasses is false. 
    CLASS_MODIFIERS_CHANGE_NOT_IMPLEMENTEDThe new class version has different modifiers and and canUnrestrictedlyRedefineClasses is false. 
    METHOD_MODIFIERS_CHANGE_NOT_IMPLEMENTEDA method in the new class version has different modifiers than its counterpart in the old class version and and canUnrestrictedlyRedefineClasses is false. 
    VM_DEADThe virtual machine is not running. 
    SetDefaultStratum Command (19)
    Set the default stratum.
    Out Data
    stringstratumIDdefault stratum, or empty string to use reference type default. 
    Reply Data
    (None)
    Error Data
    NOT_IMPLEMENTEDThe functionality is not implemented in this virtual machine. 
    VM_DEADThe virtual machine is not running. 

    ReferenceType Command Set (2)

    Signature Command (1)
    Returns the JNI signature of a reference type. JNI signature formats are described in the Java Native Inteface Specification

    For primitive classes the returned signature is the signature of the corresponding primitive type; for example, "I" is returned as the signature of the class represented by java.lang.Integer.TYPE.

    Out Data
    referenceTypeIDrefTypeThe reference type ID. 
    Reply Data
    stringsignatureThe JNI signature for the reference type. 
    Error Data
    INVALID_CLASSrefType is not the ID of a reference type. 
    INVALID_OBJECTrefType is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    ClassLoader Command (2)
    Returns the instance of java.lang.ClassLoader which loaded a given reference type. If the reference type was loaded by the system class loader, the returned object ID is null.
    Out Data
    referenceTypeIDrefTypeThe reference type ID. 
    Reply Data
    classLoaderIDclassLoaderThe class loader for the reference type.  
    Error Data
    INVALID_CLASSrefType is not the ID of a reference type. 
    INVALID_OBJECTrefType is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    Modifiers Command (3)
    Returns the modifiers (also known as access flags) for a reference type. The returned bit mask contains information on the declaration of the reference type. If the reference type is an array or a primitive class (for example, java.lang.Integer.TYPE), the value of the returned bit mask is undefined.
    Out Data
    referenceTypeIDrefTypeThe reference type ID. 
    Reply Data
    intmodBitsModifier bits as defined in the VM Specification 
    Error Data
    INVALID_CLASSrefType is not the ID of a reference type. 
    INVALID_OBJECTrefType is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    Fields Command (4)
    Returns information for each field in a reference type. Inherited fields are not included. The field list will include any synthetic fields created by the compiler. Fields are returned in the order they occur in the class file.
    Out Data
    referenceTypeIDrefTypeThe reference type ID. 
    Reply Data
    intdeclaredNumber of declared fields. 
    Repeated declared times:
    fieldIDfieldIDField ID. 
    stringnameName of field. 
    stringsignatureJNI Signature of field. 
    intmodBitsThe modifier bit flags (also known as access flags) which provide additional information on the field declaration. Individual flag values are defined in the VM Specification.In addition, The 0xf0000000 bit identifies the field as synthetic, if the synthetic attribute capability is available. 
    Error Data
    CLASS_NOT_PREPAREDClass has been loaded but not yet prepared. 
    INVALID_CLASSrefType is not the ID of a reference type. 
    INVALID_OBJECTrefType is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    Methods Command (5)
    Returns information for each method in a reference type. Inherited methodss are not included. The list of methods will include constructors (identified with the name "<init>"), the initialization method (identified with the name "<clinit>") if present, and any synthetic methods created by the compiler. Methods are returned in the order they occur in the class file.
    Out Data
    referenceTypeIDrefTypeThe reference type ID. 
    Reply Data
    intdeclaredNumber of declared methods. 
    Repeated declared times:
    methodIDmethodIDMethod ID. 
    stringnameName of method. 
    stringsignatureJNI signature of method. 
    intmodBitsThe modifier bit flags (also known as access flags) which provide additional information on the method declaration. Individual flag values are defined in the VM Specification.In addition, The 0xf0000000 bit identifies the method as synthetic, if the synthetic attribute capability is available. 
    Error Data
    CLASS_NOT_PREPAREDClass has been loaded but not yet prepared. 
    INVALID_CLASSrefType is not the ID of a reference type. 
    INVALID_OBJECTrefType is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    GetValues Command (6)
    Returns the value of one or more static fields of the reference type. Each field must be member of the reference type or one of its superclasses, superinterfaces, or implemented interfaces. Access control is not enforced; for example, the values of private fields can be obtained.
    Out Data
    referenceTypeIDrefTypeThe reference type ID. 
    intfieldsThe number of values to get 
    Repeated fields times:
    fieldIDfieldIDA field to get 
    Reply Data
    intvaluesThe number of values returned 
    Repeated values times:
    valuevalueThe field value 
    Error Data
    INVALID_CLASSrefType is not the ID of a reference type. 
    INVALID_OBJECTrefType is not a known ID. 
    INVALID_FIELDIDInvalid field. 
    VM_DEADThe virtual machine is not running. 
    SourceFile Command (7)
    Returns the name of source file in which a reference type was declared.
    Out Data
    referenceTypeIDrefTypeThe reference type ID. 
    Reply Data
    stringsourceFileThe source file name. No path information for the file is included 
    Error Data
    INVALID_CLASSrefType is not the ID of a reference type. 
    INVALID_OBJECTrefType is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    NestedTypes Command (8)
    Returns the classes and interfaces directly nested within this type.Types further nested within those types are not included.
    Out Data
    referenceTypeIDrefTypeThe reference type ID. 
    Reply Data
    intclassesThe number of nested classes and interfaces 
    Repeated classes times:
    byterefTypeTagKind of following reference type.  
    referenceTypeIDtypeIDThe nested class or interface ID. 
    Error Data
    INVALID_CLASSrefType is not the ID of a reference type. 
    INVALID_OBJECTrefType is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    Status Command (9)
    Returns the current status of the reference type. The status indicates the extent to which the reference type has been initialized, as described in the VM specification. The returned status bits are undefined for array types and for primitive classes (such as java.lang.Integer.TYPE).
    Out Data
    referenceTypeIDrefTypeThe reference type ID. 
    Reply Data
    intstatusStatus bits:See JDWP.ClassStatus 
    Error Data
    INVALID_CLASSrefType is not the ID of a reference type. 
    INVALID_OBJECTrefType is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    Interfaces Command (10)
    Returns the interfaces declared as implemented by this class. Interfaces indirectly implemented (extended by the implemented interface or implemented by a superclass) are not included.
    Out Data
    referenceTypeIDrefTypeThe reference type ID. 
    Reply Data
    intinterfacesThe number of implemented interfaces 
    Repeated interfaces times:
    interfaceIDinterfaceTypeimplemented interface. 
    Error Data
    INVALID_CLASSrefType is not the ID of a reference type. 
    INVALID_OBJECTrefType is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    ClassObject Command (11)
    Returns the class object corresponding to this type.
    Out Data
    referenceTypeIDrefTypeThe reference type ID. 
    Reply Data
    classObjectIDclassObjectclass object. 
    Error Data
    INVALID_CLASSrefType is not the ID of a reference type. 
    INVALID_OBJECTrefType is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    SourceDebugExtension Command (12)
    Returns the value of the SourceDebugExtension attribute. Since JDWP version 1.4.
    Out Data
    referenceTypeIDrefTypeThe reference type ID. 
    Reply Data
    stringextensionextension attribute 
    Error Data
    INVALID_CLASSrefType is not the ID of a reference type. 
    INVALID_OBJECTrefType is not a known ID. 
    ABSENT_INFORMATIONIf the extension is not specified. 
    NOT_IMPLEMENTEDThe functionality is not implemented in this virtual machine. 
    VM_DEADThe virtual machine is not running. 

    ClassType Command Set (3)

    Superclass Command (1)
    Returns the immediate superclass of a class.
    Out Data
    classIDclazzThe class type ID. 
    Reply Data
    classIDsuperclassThe superclass (null if the class ID for java.lang.Object is specified). 
    Error Data
    INVALID_CLASSclazz is not the ID of a class. 
    INVALID_OBJECTclazz is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    SetValues Command (2)
    Sets the value of one or more static fields. Each field must be member of the class type or one of its superclasses, superinterfaces, or implemented interfaces. Access control is not enforced; for example, the values of private fields can be set. Final fields cannot be set.For primitive values, the value's type must match the field's type exactly. For object values, there must exist a widening reference conversion from the value's type to the field's type and the field's type must be loaded.
    Out Data
    classIDclazzThe class type ID. 
    intvaluesThe number of fields to set. 
    Repeated values times:
    fieldIDfieldIDField to set. 
    untagged-valuevalueValue to put in the field. 
    Reply Data
    (None)
    Error Data
    INVALID_CLASSclazz is not the ID of a class. 
    CLASS_NOT_PREPAREDClass has been loaded but not yet prepared. 
    INVALID_OBJECTclazz is not a known ID or a value of an object field is not a known ID. 
    INVALID_FIELDIDInvalid field. 
    VM_DEADThe virtual machine is not running. 
    InvokeMethod Command (3)
    Invokes a static method. The method must be member of the class type or one of its superclasses, superinterfaces, or implemented interfaces. Access control is not enforced; for example, private methods can be invoked.

    The method invocation will occur in the specified thread. Method invocation can occur only if the specified thread has been suspended by an event. Method invocation is not supported when the target VM has been suspended by the front-end.

    The specified method is invoked with the arguments in the specified argument list. The method invocation is synchronous; the reply packet is not sent until the invoked method returns in the target VM. The return value (possibly the void value) is included in the reply packet. If the invoked method throws an exception, the exception object ID is set in the reply packet; otherwise, the exception object ID is null.

    For primitive arguments, the argument value's type must match the argument's type exactly. For object arguments, there must exist a widening reference conversion from the argument value's type to the argument's type and the argument's type must be loaded.

    By default, all threads in the target VM are resumed while the method is being invoked if they were previously suspended by an event or by command. This is done to prevent the deadlocks that will occur if any of the threads own monitors that will be needed by the invoked method. It is possible that breakpoints or other events might occur during the invocation. Note, however, that this implicit resume acts exactly like the ThreadReference resume command, so if the thread's suspend count is greater than 1, it will remain in a suspended state during the invocation. By default, when the invocation completes, all threads in the target VM are suspended, regardless their state before the invocation.

    The resumption of other threads during the invoke can be prevented by specifying the INVOKE_SINGLE_THREADED bit flag in the options field; however, there is no protection against or recovery from the deadlocks described above, so this option should be used with great caution. Only the specified thread will be resumed (as described for all threads above). Upon completion of a single threaded invoke, the invoking thread will be suspended once again. Note that any threads started during the single threaded invocation will not be suspended when the invocation completes.

    If the target VM is disconnected during the invoke (for example, through the VirtualMachine dispose command) the method invocation continues.

    Out Data
    classIDclazzThe class type ID. 
    threadIDthreadThe thread in which to invoke. 
    methodIDmethodIDThe method to invoke. 
    intarguments 
    Repeated arguments times:
    valueargThe argument value. 
    intoptionsInvocation options 
    Reply Data
    valuereturnValueThe returned value. 
    tagged-objectIDexceptionThe thrown exception. 
    Error Data
    INVALID_CLASSclazz is not the ID of a class. 
    INVALID_OBJECTclazz is not a known ID. 
    INVALID_METHODIDmethodID is not the ID of a method. 
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    THREAD_NOT_SUSPENDEDIf the specified thread has not been suspended by an event. 
    VM_DEADThe virtual machine is not running. 
    NewInstance Command (4)
    Creates a new object of this type, invoking the specified constructor. The constructor method ID must be a member of the class type.

    Instance creation will occur in the specified thread. Instance creation can occur only if the specified thread has been suspended by an event. Method invocation is not supported when the target VM has been suspended by the front-end.

    The specified constructor is invoked with the arguments in the specified argument list. The constructor invocation is synchronous; the reply packet is not sent until the invoked method returns in the target VM. The return value (possibly the void value) is included in the reply packet. If the constructor throws an exception, the exception object ID is set in the reply packet; otherwise, the exception object ID is null.

    For primitive arguments, the argument value's type must match the argument's type exactly. For object arguments, there must exist a widening reference conversion from the argument value's type to the argument's type and the argument's type must be loaded.

    By default, all threads in the target VM are resumed while the method is being invoked if they were previously suspended by an event or by command. This is done to prevent the deadlocks that will occur if any of the threads own monitors that will be needed by the invoked method. It is possible that breakpoints or other events might occur during the invocation. Note, however, that this implicit resume acts exactly like the ThreadReference resume command, so if the thread's suspend count is greater than 1, it will remain in a suspended state during the invocation. By default, when the invocation completes, all threads in the target VM are suspended, regardless their state before the invocation.

    The resumption of other threads during the invoke can be prevented by specifying the INVOKE_SINGLE_THREADED bit flag in the options field; however, there is no protection against or recovery from the deadlocks described above, so this option should be used with great caution. Only the specified thread will be resumed (as described for all threads above). Upon completion of a single threaded invoke, the invoking thread will be suspended once again. Note that any threads started during the single threaded invocation will not be suspended when the invocation completes.

    If the target VM is disconnected during the invoke (for example, through the VirtualMachine dispose command) the method invocation continues.

    Out Data
    classIDclazzThe class type ID. 
    threadIDthreadThe thread in which to invoke the constructor. 
    methodIDmethodIDThe constructor to invoke. 
    intarguments 
    Repeated arguments times:
    valueargThe argument value. 
    intoptionsConstructor invocation options 
    Reply Data
    tagged-objectIDnewObjectThe newly created object, or null if the constructor threw an exception. 
    tagged-objectIDexceptionThe thrown exception, if any; otherwise, null. 
    Error Data
    INVALID_CLASSclazz is not the ID of a class. 
    INVALID_OBJECTclazz is not a known ID or a value of an object parameter is not a known ID.. 
    INVALID_METHODIDmethodID is not the ID of a method. 
    INVALID_OBJECTIf this reference type has been unloaded and garbage collected. 
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    THREAD_NOT_SUSPENDEDIf the specified thread has not been suspended by an event. 
    VM_DEADThe virtual machine is not running. 

    ArrayType Command Set (4)

    NewInstance Command (1)
    Creates a new array object of this type with a given length.
    Out Data
    arrayTypeIDarrTypeThe array type of the new instance. 
    intlengthThe length of the array. 
    Reply Data
    tagged-objectIDnewArrayThe newly created array object.  
    Error Data
    INVALID_ARRAYThe array is invalid. 
    INVALID_OBJECTIf this reference type has been unloaded and garbage collected. 
    VM_DEADThe virtual machine is not running. 

    InterfaceType Command Set (5)

    Method Command Set (6)

    LineTable Command (1)
    Returns line number information for the method. The line table maps source line numbers to the initial code index of the line. The line table is ordered by code index (from lowest to highest).
    Out Data
    referenceTypeIDrefTypeThe class. 
    methodIDmethodIDThe method. 
    Reply Data
    longstartLowest valid code index for the method. 
    longendHighest valid code index for the method. 
    intlinesThe number of lines. 
    Repeated lines times:
    longlineCodeIndexInitial code index of the line (unsigned). 
    intlineNumberLine number. 
    Error Data
    INVALID_CLASSrefType is not the ID of a reference type. 
    INVALID_OBJECTrefType is not a known ID. 
    INVALID_METHODIDmethodID is not the ID of a method. 
    VM_DEADThe virtual machine is not running. 
    VariableTable Command (2)
    Returns variable information for the method. The variable table includes arguments and locals declared within the method. For instance methods, the "this" reference is included in the table. Also, synthetic variables may be present.
    Out Data
    referenceTypeIDrefTypeThe class. 
    methodIDmethodIDThe method. 
    Reply Data
    intargCntThe number of words in the frame used by arguments. Eight-byte arguments use two words; all others use one.  
    intslotsThe number of variables. 
    Repeated slots times:
    longcodeIndexFirst code index at which the variable is visible (unsigned). Used in conjunction with length. The variable can be get or set only when the current codeIndex <= current frame code index < codeIndex + length  
    stringnameThe variable's name. 
    stringsignatureThe variable type's JNI signature. 
    intlengthUnsigned value used in conjunction with codeIndex. The variable can be get or set only when the current codeIndex <= current frame code index < code index + length  
    intslotThe local variable's index in its frame 
    Error Data
    INVALID_CLASSrefType is not the ID of a reference type. 
    INVALID_OBJECTrefType is not a known ID. 
    INVALID_METHODIDmethodID is not the ID of a method. 
    ABSENT_INFORMATIONthere is no variable information for the method. 
    VM_DEADThe virtual machine is not running. 
    Bytecodes Command (3)
    Retrieve the method's bytecodes as defined in the JVM Specification.
    Out Data
    referenceTypeIDrefTypeThe class. 
    methodIDmethodIDThe method. 
    Reply Data
    intbytes 
    Repeated bytes times:
    bytebytecodeA Java bytecode. 
    Error Data
    INVALID_CLASSrefType is not the ID of a reference type. 
    INVALID_OBJECTrefType is not a known ID. 
    INVALID_METHODIDmethodID is not the ID of a method. 
    NOT_IMPLEMENTEDIf the target virtual machine does not support the retrieval of bytecodes. 
    VM_DEADThe virtual machine is not running. 
    IsObsolete Command (4)
    Determine if this method is obsolete.
    Out Data
    referenceTypeIDrefTypeThe class. 
    methodIDmethodIDThe method. 
    Reply Data
    booleanisObsoletetrue if this method has been replacedby a non-equivalent method usingthe RedefineClasses command 
    Error Data
    INVALID_CLASSrefType is not the ID of a reference type. 
    INVALID_OBJECTrefType is not a known ID. 
    INVALID_METHODIDmethodID is not the ID of a method. 
    NOT_IMPLEMENTEDIf the target virtual machine does not support this query. 
    VM_DEADThe virtual machine is not running. 

    Field Command Set (8)

    ObjectReference Command Set (9)

    ReferenceType Command (1)
    Returns the runtime type of the object. The runtime type will be a class or an array.
    Out Data
    objectIDobjectThe object ID 
    Reply Data
    byterefTypeTagKind of following reference type.  
    referenceTypeIDtypeIDThe runtime reference type. 
    Error Data
    INVALID_OBJECTIf this reference type has been unloaded and garbage collected. 
    VM_DEADThe virtual machine is not running. 
    GetValues Command (2)
    Returns the value of one or more instance fields. Each field must be member of the object's type or one of its superclasses, superinterfaces, or implemented interfaces. Access control is not enforced; for example, the values of private fields can be obtained.
    Out Data
    objectIDobjectThe object ID 
    intfieldsThe number of values to get 
    Repeated fields times:
    fieldIDfieldIDField to get. 
    Reply Data
    intvaluesThe number of values returned 
    Repeated values times:
    valuevalueThe field value 
    Error Data
    INVALID_OBJECTIf this reference type has been unloaded and garbage collected. 
    INVALID_FIELDIDInvalid field. 
    VM_DEADThe virtual machine is not running. 
    SetValues Command (3)
    Sets the value of one or more instance fields. Each field must be member of the object's type or one of its superclasses, superinterfaces, or implemented interfaces. Access control is not enforced; for example, the values of private fields can be set. For primitive values, the value's type must match the field's type exactly. For object values, there must be a widening reference conversion from the value's type to the field's type and the field's type must be loaded.
    Out Data
    objectIDobjectThe object ID 
    intvaluesThe number of fields to set. 
    Repeated values times:
    fieldIDfieldIDField to set. 
    untagged-valuevalueValue to put in the field. 
    Reply Data
    (None)
    Error Data
    INVALID_OBJECTIf this reference type has been unloaded and garbage collected. 
    INVALID_FIELDIDInvalid field. 
    VM_DEADThe virtual machine is not running. 
    MonitorInfo Command (5)
    Returns monitor information for an object. All threads int the VM must be suspended.
    Out Data
    objectIDobjectThe object ID 
    Reply Data
    threadIDownerThe monitor owner, or null if it is not currently owned. 
    intentryCountThe number of times the monitor has been entered. 
    intwaitersThe number of threads that are waiting for the monitor 0 if there is no current owner 
    Repeated waiters times:
    threadIDthreadA thread waiting for this monitor. 
    Error Data
    INVALID_OBJECTIf this reference type has been unloaded and garbage collected. 
    NOT_IMPLEMENTEDThe functionality is not implemented in this virtual machine. 
    VM_DEADThe virtual machine is not running. 
    InvokeMethod Command (6)
    Invokes a instance method. The method must be member of the object's type or one of its superclasses, superinterfaces, or implemented interfaces. Access control is not enforced; for example, private methods can be invoked.

    The method invocation will occur in the specified thread. Method invocation can occur only if the specified thread has been suspended by an event. Method invocation is not supported when the target VM has been suspended by the front-end.

    The specified method is invoked with the arguments in the specified argument list. The method invocation is synchronous; the reply packet is not sent until the invoked method returns in the target VM. The return value (possibly the void value) is included in the reply packet. If the invoked method throws an exception, the exception object ID is set in the reply packet; otherwise, the exception object ID is null.

    For primitive arguments, the argument value's type must match the argument's type exactly. For object arguments, there must be a widening reference conversion from the argument value's type to the argument's type and the argument's type must be loaded.

    By default, all threads in the target VM are resumed while the method is being invoked if they were previously suspended by an event or by command. This is done to prevent the deadlocks that will occur if any of the threads own monitors that will be needed by the invoked method. It is possible that breakpoints or other events might occur during the invocation. Note, however, that this implicit resume acts exactly like the ThreadReference resume command, so if the thread's suspend count is greater than 1, it will remain in a suspended state during the invocation. By default, when the invocation completes, all threads in the target VM are suspended, regardless their state before the invocation.

    The resumption of other threads during the invoke can be prevented by specifying the INVOKE_SINGLE_THREADED bit flag in the options field; however, there is no protection against or recovery from the deadlocks described above, so this option should be used with great caution. Only the specified thread will be resumed (as described for all threads above). Upon completion of a single threaded invoke, the invoking thread will be suspended once again. Note that any threads started during the single threaded invocation will not be suspended when the invocation completes.

    If the target VM is disconnected during the invoke (for example, through the VirtualMachine dispose command) the method invocation continues.

    Out Data
    objectIDobjectThe object ID 
    threadIDthreadThe thread in which to invoke. 
    classIDclazzThe class type. 
    methodIDmethodIDThe method to invoke. 
    intargumentsThe number of arguments. 
    Repeated arguments times:
    valueargThe argument value. 
    intoptionsInvocation options 
    Reply Data
    valuereturnValueThe returned value, or null if an exception is thrown. 
    tagged-objectIDexceptionThe thrown exception, if any. 
    Error Data
    INVALID_OBJECTIf this reference type has been unloaded and garbage collected. 
    INVALID_CLASSclazz is not the ID of a reference type. 
    INVALID_METHODIDmethodID is not the ID of a method. 
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    THREAD_NOT_SUSPENDEDIf the specified thread has not been suspended by an event. 
    VM_DEADThe virtual machine is not running. 
    DisableCollection Command (7)
    Prevents garbage collection for the given object. By default all objects in back-end replies may be collected at any time the target VM is running. A call to this command guarantees that the object will not be collected. The EnableCollection command can be used to allow collection once again.

    Note that while the target VM is suspended, no garbage collection will occur because all threads are suspended. The typical examination of variables, fields, and arrays during the suspension is safe without explicitly disabling garbage collection.

    This method should be used sparingly, as it alters the pattern of garbage collection in the target VM and, consequently, may result in application behavior under the debugger that differs from its non-debugged behavior.

    Out Data
    objectIDobjectThe object ID 
    Reply Data
    (None)
    Error Data
    INVALID_OBJECTIf this reference type has been unloaded and garbage collected. 
    VM_DEADThe virtual machine is not running. 
    EnableCollection Command (8)
    Permits garbage collection for this object. By default all objects returned by the JDWP may be collected at any time the target VM is running. A call to this command is necessary only if garbage collection was previously disabled with the DisableCollection command.
    Out Data
    objectIDobjectThe object ID 
    Reply Data
    (None)
    Error Data
    VM_DEADThe virtual machine is not running. 
    IsCollected Command (9)
    Determines whether an object has been garbage collected in the target VM.
    Out Data
    objectIDobjectThe object ID 
    Reply Data
    booleanisCollectedtrue if the object has been collected; false otherwise 
    Error Data
    INVALID_OBJECTIf this reference type has been unloaded and garbage collected. 
    VM_DEADThe virtual machine is not running. 

    StringReference Command Set (10)

    Value Command (1)
    Returns the characters contained in the string.
    Out Data
    objectIDstringObjectThe String object ID.  
    Reply Data
    stringstringValueThe value of the String. 
    Error Data
    INVALID_STRINGThe string is invalid. 
    INVALID_OBJECTIf this reference type has been unloaded and garbage collected. 
    VM_DEADThe virtual machine is not running. 

    ThreadReference Command Set (11)

    Name Command (1)
    Returns the thread name.
    Out Data
    threadIDthreadThe thread object ID.  
    Reply Data
    stringthreadNameThe thread name. 
    Error Data
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    INVALID_OBJECTthread is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    Suspend Command (2)
    Suspends the thread.

    Unlike java.lang.Thread.suspend(), suspends of both the virtual machine and individual threads are counted. Before a thread will run again, it must be resumed the same number of times it has been suspended.

    Suspending single threads with command has the same dangers java.lang.Thread.suspend(). If the suspended thread holds a monitor needed by another running thread, deadlock is possible in the target VM (at least until the suspended thread is resumed again).

    The suspended thread is guaranteed to remain suspended until resumed through one of the JDI resume methods mentioned above; the application in the target VM cannot resume the suspended thread through {@link java.lang.Thread#resume}.

    Note that this doesn't change the status of the thread (see the ThreadStatus command.) For example, if it was Running, it will still appear running to other threads.

    Out Data
    threadIDthreadThe thread object ID.  
    Reply Data
    (None)
    Error Data
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    INVALID_OBJECTthread is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    Resume Command (3)
    Resumes the execution of a given thread. If this thread was not previously suspended by the front-end, calling this command has no effect. Otherwise, the count of pending suspends on this thread is decremented. If it is decremented to 0, the thread will continue to execute.
    Out Data
    threadIDthreadThe thread object ID.  
    Reply Data
    (None)
    Error Data
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    INVALID_OBJECTthread is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    Status Command (4)
    Returns the current status of a thread. The thread status reply indicates the thread status the last time it was running. the suspend status provides information on the thread's suspension, if any.
    Out Data
    threadIDthreadThe thread object ID.  
    Reply Data
    intthreadStatusOne of the thread status codes See JDWP.ThreadStatus 
    intsuspendStatusOne of the suspend status codes See JDWP.SuspendStatus 
    Error Data
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    INVALID_OBJECTthread is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    ThreadGroup Command (5)
    Returns the thread group that contains a given thread.
    Out Data
    threadIDthreadThe thread object ID.  
    Reply Data
    threadGroupIDgroupThe thread group of this thread.  
    Error Data
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    INVALID_OBJECTthread is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    Frames Command (6)
    Returns the current call stack of a suspended thread. The sequence of frames starts with the currently executing frame, followed by its caller, and so on. The thread must be suspended, and the returned frameID is valid only while the thread is suspended.
    Out Data
    threadIDthreadThe thread object ID.  
    intstartFrameThe index of the first frame to retrieve. 
    intlengthThe count of frames to retrieve (-1 means all remaining).  
    Reply Data
    intframesThe number of frames retreived 
    Repeated frames times:
    frameIDframeIDThe ID of this frame.  
    locationlocationThe current location of this frame 
    Error Data
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    INVALID_OBJECTthread is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    FrameCount Command (7)
    Returns the count of frames on this thread's stack. The thread must be suspended, and the returned count is valid only while the thread is suspended. Returns JDWP.Error.errorThreadNotSuspended if not suspended.
    Out Data
    threadIDthreadThe thread object ID.  
    Reply Data
    intframeCountThe count of frames on this thread's stack.  
    Error Data
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    INVALID_OBJECTthread is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    OwnedMonitors Command (8)
    Returns the objects whose monitors have been entered by this thread. The thread must be suspended, and the returned information is relevant only while the thread is suspended.
    Out Data
    threadIDthreadThe thread object ID.  
    Reply Data
    intownedThe number of owned monitors 
    Repeated owned times:
    tagged-objectIDmonitorAn owned monitor 
    Error Data
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    INVALID_OBJECTthread is not a known ID. 
    NOT_IMPLEMENTEDThe functionality is not implemented in this virtual machine. 
    VM_DEADThe virtual machine is not running. 
    CurrentContendedMonitor Command (9)
    Returns the object, if any, for which this thread is waiting for monitor entry or with java.lang.Object.wait. The thread must be suspended, and the returned information is relevant only while the thread is suspended.
    Out Data
    threadIDthreadThe thread object ID.  
    Reply Data
    tagged-objectIDmonitorThe contended monitor, or null if there is no current contended monitor.  
    Error Data
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    INVALID_OBJECTthread is not a known ID. 
    NOT_IMPLEMENTEDThe functionality is not implemented in this virtual machine. 
    VM_DEADThe virtual machine is not running. 
    Stop Command (10)
    Stops the thread with an asynchronous exception, as if done by java.lang.Thread.stop
    Out Data
    threadIDthreadThe thread object ID.  
    objectIDthrowableAsynchronous exception. This object must be an instance of java.lang.Throwable or a subclass 
    Reply Data
    (None)
    Error Data
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    INVALID_OBJECTIf thread is not a known ID or the asynchronous exception has been garbage collected. 
    VM_DEADThe virtual machine is not running. 
    Interrupt Command (11)
    Interrupt the thread, as if done by java.lang.Thread.interrupt
    Out Data
    threadIDthreadThe thread object ID.  
    Reply Data
    (None)
    Error Data
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    INVALID_OBJECTthread is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    SuspendCount Command (12)
    Get the suspend count for this thread. The suspend count is the number of times the thread has been suspended through the thread-level or VM-level suspend commands without a corresponding resume
    Out Data
    threadIDthreadThe thread object ID.  
    Reply Data
    intsuspendCountThe number of outstanding suspends of this thread.  
    Error Data
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    INVALID_OBJECTthread is not a known ID. 
    VM_DEADThe virtual machine is not running. 

    ThreadGroupReference Command Set (12)

    Name Command (1)
    Returns the thread group name.
    Out Data
    threadGroupIDgroupThe thread group object ID.  
    Reply Data
    stringgroupNameThe thread group's name. 
    Error Data
    INVALID_THREAD_GROUPThread group invalid. 
    INVALID_OBJECTgroup is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    Parent Command (2)
    Returns the thread group, if any, which contains a given thread group.
    Out Data
    threadGroupIDgroupThe thread group object ID.  
    Reply Data
    threadGroupIDparentGroupThe parent thread group object, or null if the given thread group is a top-level thread group 
    Error Data
    INVALID_THREAD_GROUPThread group invalid. 
    INVALID_OBJECTgroup is not a known ID. 
    VM_DEADThe virtual machine is not running. 
    Children Command (3)
    Returns the threads and thread groups directly contained in this thread group. Threads and thread groups in child thread groups are not included.
    Out Data
    threadGroupIDgroupThe thread group object ID.  
    Reply Data
    intchildThreadsThe number of child threads.  
    Repeated childThreads times:
    threadIDchildThreadA direct child thread ID.  
    intchildGroupsThe number of child thread groups.  
    Repeated childGroups times:
    threadGroupIDchildGroupA direct child thread group ID.  
    Error Data
    INVALID_THREAD_GROUPThread group invalid. 
    INVALID_OBJECTgroup is not a known ID. 
    VM_DEADThe virtual machine is not running. 

    ArrayReference Command Set (13)

    Length Command (1)
    Returns the number of components in a given array.
    Out Data
    arrayIDarrayObjectThe array object ID.  
    Reply Data
    intarrayLengthThe length of the array. 
    Error Data
    INVALID_OBJECTarrayObject is not a known ID. 
    INVALID_ARRAYThe array is invalid. 
    VM_DEADThe virtual machine is not running. 
    GetValues Command (2)
    Returns a range of array components. The specified range must be within the bounds of the array.
    Out Data
    arrayIDarrayObjectThe array object ID.  
    intfirstIndexThe first index to retrieve. 
    intlengthThe number of components to retrieve. 
    Reply Data
    arrayregionvaluesThe retrieved values. If the values are objects, they are tagged-values; otherwise, they are untagged-values 
    Error Data
    INVALID_LENGTHIf index is beyond the end of this array. 
    INVALID_OBJECTarrayObject is not a known ID. 
    INVALID_ARRAYThe array is invalid. 
    VM_DEADThe virtual machine is not running. 
    SetValues Command (3)
    Sets a range of array components. The specified range must be within the bounds of the array. For primitive values, each value's type must match the array component type exactly. For object values, there must be a widening reference conversion from the value's type to the array component type and the array component type must be loaded.
    Out Data
    arrayIDarrayObjectThe array object ID.  
    intfirstIndexThe first index to set. 
    intvaluesThe number of values to set.  
    Repeated values times:
    untagged-valuevalueA value to set.  
    Reply Data
    (None)
    Error Data
    INVALID_LENGTHIf index is beyond the end of this array. 
    INVALID_OBJECTarrayObject is not a known ID. 
    INVALID_ARRAYThe array is invalid. 
    VM_DEADThe virtual machine is not running. 

    ClassLoaderReference Command Set (14)

    VisibleClasses Command (1)
    Returns a list of all classes which this class loader has been requested to load. This class loader is considered to be an initiating class loader for each class in the returned list. The list contains each reference type defined by this loader and any types for which loading was delegated by this class loader to another class loader.

    The visible class list has useful properties with respect to the type namespace. A particular type name will occur at most once in the list. Each field or variable declared with that type name in a class defined by this class loader must be resolved to that single type.

    No ordering of the returned list is guaranteed.

    Out Data
    classLoaderIDclassLoaderObjectThe class loader object ID.  
    Reply Data
    intclassesThe number of visible classes.  
    Repeated classes times:
    byterefTypeTagKind of following reference type.  
    referenceTypeIDtypeIDA class visible to this class loader. 
    Error Data
    INVALID_OBJECTIf this reference type has been unloaded and garbage collected. 
    INVALID_CLASS_LOADERThe class loader is invalid. 
    VM_DEADThe virtual machine is not running. 

    EventRequest Command Set (15)

    Set Command (1)
    Set an event request. When the event described by this request occurs, an event is sent from the target VM.
    Out Data
    byteeventKindEvent kind to request. See JDWP.EventKind for a complete list of events that can be requested.  
    bytesuspendPolicyWhat threads are suspended when this event occurs? Note that the order of events and command replies accurately reflects the order in which threads are suspended and resumed. For example, if a VM-wide resume is processed before an event occurs which suspends the VM, the reply to the resume command will be written to the transport before the suspending event. 
    intmodifiersConstraints used to control the number of generated events. Modifiers specify additional tests that an event must satisfy before it is placed in the event queue. Events are filtered by applying each modifier to an event in the order they are specified in this collection Only events that satisfy all modifiers are reported.

    Filtering can improve debugger performance dramatically by reducing the amount of event traffic sent from the target VM to the debugger VM.  

    Repeated modifiers times:
    bytemodKindModifier kind 
    Case Count - if modKind is 1: Limit the requested event to be reported at most once after a given number of occurrences. The event is not reported the first count - 1 times this filter is reached. To request a one-off event, call this method with a count of 1.

    Once the count reaches 0, any subsequent filters in this request are applied. If none of those filters cause the event to be suppressed, the event is reported. Otherwise, the event is not reported. In either case subsequent events are never reported for this request. This modifier can be used with any event kind. 

    intcountCount before event. One for one-off. 
    Case Conditional - if modKind is 2: Conditional on expression 
    intexprIDFor the future 
    Case ThreadOnly - if modKind is 3: Restricts reported events to those in the given thread. This modifier can be used with any event kind except for class unload.  
    threadIDthreadRequired thread 
    Case ClassOnly - if modKind is 4: For class prepare events, restricts the events generated by this request to be the preparation of the given reference type and any subtypes. For other events, restricts the events generated by this request to those whose location is in the given reference type or any of its subtypes. An event will be generated for any location in a reference type that can be safely cast to the given reference type. This modifier can be used with any event kind except class unload, thread start, and thread end.  
    referenceTypeIDclazzRequired class 
    Case ClassMatch - if modKind is 5: Restricts reported events to those for classes whose name matches the given restricted regular expression. For class prepare events, the prepared class name is matched. For class unload events, the unloaded class name is matched. For other events, the class name of the event's location is matched. This modifier can be used with any event kind except thread start and thread end.  
    stringclassPatternRequired class pattern. Matches are limited to exact matches of the given class pattern and matches of patterns that begin or end with '*'; for example, "*.Foo" or "java.*".  
    Case ClassExclude - if modKind is 6: Restricts reported events to those for classes whose name does not match the given restricted regular expression. For class prepare events, the prepared class name is matched. For class unload events, the unloaded class name is matched. For other events, the class name of the event's location is matched. This modifier can be used with any event kind except thread start and thread end.  
    stringclassPatternDisallowed class pattern. Matches are limited to exact matches of the given class pattern and matches of patterns that begin or end with '*'; for example, "*.Foo" or "java.*".  
    Case LocationOnly - if modKind is 7: Restricts reported events to those that occur at the given location. This modifier can be used with breakpoint, field access, field modification, step, and exception event kinds.  
    locationlocRequired location 
    Case ExceptionOnly - if modKind is 8: Restricts reported exceptions by their class and whether they are caught or uncaught. This modifier can be used with exception event kinds only.  
    referenceTypeIDexceptionOrNullException to report. Null (0) means report exceptions of all types. A non-null type restricts the reported exception events to exceptions of the given type or any of its subtypes.  
    booleancaughtReport caught exceptions 
    booleanuncaughtReport uncaught exceptions. Note that it is not always possible to determine whether an exception is caught or uncaught at the time it is thrown. See the exception event catch location under composite events for more information.  
    Case FieldOnly - if modKind is 9: Restricts reported events to those that occur for a given field. This modifier can be used with field access and field modification event kinds only.  
    referenceTypeIDdeclaringType in which field is declared. 
    fieldIDfieldIDRequired field 
    Case Step - if modKind is 10: Restricts reported step events to those which satisfy depth and size constraints. This modifier can be used with step event kinds only.  
    threadIDthreadThread in which to step 
    intsizesize of each step. See JDWP.StepSize 
    intdepthrelative call stack limit. See JDWP.StepDepth 
    Case InstanceOnly - if modKind is 11: Restricts reported events to those whose active 'this' object is the given object. Match value is the null object for static methods. This modifier can be used with any event kind except class prepare, class unload, thread start, and thread end. Introduced in JDWP version 1.4. 
    objectIDinstanceRequired 'this' object 
    Reply Data
    intrequestIDID of created request 
    Error Data
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    INVALID_CLASSInvalid class. 
    INVALID_STRINGThe string is invalid. 
    INVALID_OBJECTIf this reference type has been unloaded and garbage collected. 
    INVALID_COUNTThe count is invalid. 
    INVALID_FIELDIDInvalid field. 
    INVALID_METHODIDInvalid method. 
    INVALID_LOCATIONInvalid location. 
    INVALID_EVENT_TYPEThe specified event type id is not recognized. 
    NOT_IMPLEMENTEDThe functionality is not implemented in this virtual machine. 
    VM_DEADThe virtual machine is not running. 
    Clear Command (2)
    Clear an event request.
    Out Data
    byteeventEvent type to clear 
    intrequestIDID of request to clear 
    Reply Data
    (None)
    Error Data
    VM_DEADThe virtual machine is not running. 
    ClearAllBreakpoints Command (3)
    Removes all set breakpoints.
    Out Data
    (None)
    Reply Data
    (None)
    Error Data
    VM_DEADThe virtual machine is not running. 

    StackFrame Command Set (16)

    GetValues Command (1)
    Returns the value of one or more local variables in a given frame. Each variable must be visible at the frame's code index. Even if local variable information is not available, values can be retrieved if the front-end is able to determine the correct local variable index. (Typically, this index can be determined for method arguments from the method signature without access to the local variable table information.)
    Out Data
    threadIDthreadThe frame's thread.  
    frameIDframeThe frame ID.  
    intslotsThe number of values to get.  
    Repeated slots times:
    intslotThe local variable's index in the frame.  
    bytesigbyteA tag identifying the type of the variable  
    Reply Data
    intvaluesThe number of values retrieved.  
    Repeated values times:
    valueslotValueThe value of the local variable.  
    Error Data
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    INVALID_OBJECTIf this reference type has been unloaded and garbage collected. 
    INVALID_FRAMEIDInvalid jframeID. 
    VM_DEADThe virtual machine is not running. 
    SetValues Command (2)
    Sets the value of one or more local variables. Each variable must be visible at the current frame code index. For primitive values, the value's type must match the variable's type exactly. For object values, there must be a widening reference conversion from the value's type to the variable's type and the variable's type must be loaded.

    Even if local variable information is not available, values can be set, if the front-end is able to determine the correct local variable index. (Typically, this index can be determined for method arguments from the method signature without access to the local variable table information.)

    Out Data
    threadIDthreadThe frame's thread.  
    frameIDframeThe frame ID.  
    intslotValuesThe number of values to set.  
    Repeated slotValues times:
    intslotThe slot ID.  
    valueslotValueThe value to set.  
    Reply Data
    (None)
    Error Data
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    INVALID_OBJECTIf this reference type has been unloaded and garbage collected. 
    INVALID_FRAMEIDInvalid jframeID. 
    VM_DEADThe virtual machine is not running. 
    ThisObject Command (3)
    Returns the value of the 'this' reference for this frame. If the frame's method is static or native, the reply will contain the null object reference.
    Out Data
    threadIDthreadThe frame's thread.  
    frameIDframeThe frame ID.  
    Reply Data
    tagged-objectIDobjectThisThe 'this' object for this frame.  
    Error Data
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    INVALID_OBJECTIf this reference type has been unloaded and garbage collected. 
    INVALID_FRAMEIDInvalid jframeID. 
    VM_DEADThe virtual machine is not running. 
    PopFrames Command (4)
    Pop stack frames, thru and including 'frame'.Since JDWP version 1.4.
    Out Data
    threadIDthreadThe thread object ID.  
    frameIDframeThe frame ID.  
    Reply Data
    (None)
    Error Data
    INVALID_THREADPassed thread is null, is not a valid thread or has exited. 
    INVALID_OBJECTthread is not a known ID. 
    INVALID_FRAMEIDInvalid jframeID. 
    THREAD_NOT_SUSPENDEDIf the specified thread has not been suspended by an event. 
    NO_MORE_FRAMESThere are no more Java or JNI frames on the call stack. 
    INVALID_FRAMEIDInvalid jframeID. 
    NOT_IMPLEMENTEDThe functionality is not implemented in this virtual machine. 
    VM_DEADThe virtual machine is not running. 

    ClassObjectReference Command Set (17)

    ReflectedType Command (1)
    Returns the reference type reflected by this class object.
    Out Data
    classObjectIDclassObjectThe class object.  
    Reply Data
    byterefTypeTagKind of following reference type.  
    referenceTypeIDtypeIDreflected reference type 
    Error Data
    INVALID_OBJECTIf this reference type has been unloaded and garbage collected. 
    VM_DEADThe virtual machine is not running. 

    Event Command Set (64)

    Composite Command (100)
    Several events may occur at a given time in the target VM. For example, there may be more than one breakpoint request for a given location or you might single step to the same location as a breakpoint request. These events are delivered together as a composite event. For uniformity, a composite event is always used to deliver events, even if there is only one event to report.

    The events that are grouped in a composite event are restricted in the following ways:

    Event Data
    bytesuspendPolicyWhich threads where suspended by this composite event? 
    inteventsEvents in set. 
    Repeated events times:
    byteeventKindEvent kind selector 
    Case VMStart - if eventKind is JDWP.EventKind.VM_START: Notification of initialization of a target VM. This event is received before the main thread is started and before any application code has been executed. Before this event occurs a significant amount of system code has executed and a number of system classes have been loaded. This event is always generated by the target VM, even if not explicitly requested. 
    intrequestIDRequest that generated event (or 0 if this event is automatically generated. 
    threadIDthreadInitial thread 
    Case SingleStep - if eventKind is JDWP.EventKind.SINGLE_STEP: Notification of step completion in the target VM. The step event is generated before the code at its location is executed.  
    intrequestIDRequest that generated event 
    threadIDthreadStepped thread 
    locationlocationLocation stepped to 
    Case Breakpoint - if eventKind is JDWP.EventKind.BREAKPOINT: Notification of a breakpoint in the target VM. The breakpoint event is generated before the code at its location is executed.  
    intrequestIDRequest that generated event 
    threadIDthreadthread which hit breakpoint 
    locationlocationLocation hit 
    Case MethodEntry - if eventKind is JDWP.EventKind.METHOD_ENTRY: Notification of a method invocation in the target VM. This event is generated before any code in the invoked method has executed. Method entry events are generated for both native and non-native methods.

    In some VMs method entry events can occur for a particular thread before its thread start event occurs if methods are called as part of the thread's initialization.  

    intrequestIDRequest that generated event 
    threadIDthreadthread which entered method 
    locationlocationLocation of entry 
    Case MethodExit - if eventKind is JDWP.EventKind.METHOD_EXIT: Notification of a method return in the target VM. This event is generated after all code in the method has executed, but the location of this event is the last executed location in the method. Method exit events are generated for both native and non-native methods. Method exit events are not generated if the method terminates with a thrown exception.  
    intrequestIDRequest that generated event 
    threadIDthreadthread which exited method 
    locationlocationLocation of exit 
    Case Exception - if eventKind is JDWP.EventKind.EXCEPTION: Notification of an exception in the target VM. If the exception is thrown from a non-native method, the exception event is generated at the location where the exception is thrown. If the exception is thrown from a native method, the exception event is generated at the first non-native location reached after the exception is thrown. 
    intrequestIDRequest that generated event 
    threadIDthreadThread with exception 
    locationlocationLocation of exception throw (or first non-native location after throw if thrown from a native method) 
    tagged-objectIDexceptionThrown exception 
    locationcatchLocationLocation of catch, or 0 if not caught. An exception is considered to be caught if, at the point of the throw, the current location is dynamically enclosed in a try statement that handles the exception. (See the JVM specification for details). If there is such a try statement, the catch location is the first location in the appropriate catch clause.

    If there are native methods in the call stack at the time of the exception, there are important restrictions to note about the returned catch location. In such cases, it is not possible to predict whether an exception will be handled by some native method on the call stack. Thus, it is possible that exceptions considered uncaught here will, in fact, be handled by a native method and not cause termination of the target VM. Furthermore, it cannot be assumed that the catch location returned here will ever be reached by the throwing thread. If there is a native frame between the current location and the catch location, the exception might be handled and cleared in that native method instead.

    Note that compilers can generate try-catch blocks in some cases where they are not explicit in the source code; for example, the code generated for synchronized and finally blocks can contain implicit try-catch blocks. If such an implicitly generated try-catch is present on the call stack at the time of the throw, the exception will be considered caught even though it appears to be uncaught from examination of the source code.  

    Case ThreadStart - if eventKind is JDWP.EventKind.THREAD_START: Notification of a new running thread in the target VM. The new thread can be the result of a call to java.lang.Thread.start or the result of attaching a new thread to the VM though JNI. The notification is generated by the new thread some time before its execution starts. Because of this timing, it is possible to receive other events for the thread before this event is received. (Notably, Method Entry Events and Method Exit Events might occur during thread initialization. It is also possible for the VirtualMachine AllThreads command to return a thread before its thread start event is received.

    Note that this event gives no information about the creation of the thread object which may have happened much earlier, depending on the VM being debugged.  

    intrequestIDRequest that generated event 
    threadIDthreadStarted thread 
    Case ThreadDeath - if eventKind is JDWP.EventKind.THREAD_DEATH: Notification of a completed thread in the target VM. The notification is generated by the dying thread before it terminates. Because of this timing, it is possible for {@link VirtualMachine#allThreads} to return this thread after this event is received.

    Note that this event gives no information about the lifetime of the thread object. It may or may not be collected soon depending on what references exist in the target VM.  

    intrequestIDRequest that generated event 
    threadIDthreadEnding thread 
    Case ClassPrepare - if eventKind is JDWP.EventKind.CLASS_PREPARE: Notification of a class prepare in the target VM. See the JVM specification for a definition of class preparation. Class prepare events are not generated for primtiive classes (for example, java.lang.Integer.TYPE).  
    intrequestIDRequest that generated event 
    threadIDthreadPreparing thread. In rare cases, this event may occur in a debugger system thread within the target VM. Debugger threads take precautions to prevent these events, but they cannot be avoided under some conditions, especially for some subclasses of java.lang.Error. If the event was generated by a debugger system thread, the value returned by this method is null, and if the requested suspend policy for the event was EVENT_THREAD all threads will be suspended instead, and the composite event's suspend policy will reflect this change.

    Note that the discussion above does not apply to system threads created by the target VM during its normal (non-debug) operation.  

    byterefTypeTagKind of reference type. See JDWP.TypeTag 
    referenceTypeIDtypeIDType being prepared 
    stringsignatureType signature 
    intstatusStatus of type. See JDWP.ClassStatus 
    Case ClassUnload - if eventKind is JDWP.EventKind.CLASS_UNLOAD: Notification of a class unload in the target VM.

    There are severe constraints on the debugger back-end during garbage collection, so unload information is greatly limited.  

    intrequestIDRequest that generated event 
    stringsignatureType signature 
    Case FieldAccess - if eventKind is JDWP.EventKind.FIELD_ACCESS: Notification of a field access in the target VM. Field modifications are not considered field accesses.  
    intrequestIDRequest that generated event 
    threadIDthreadAccessing thread 
    locationlocationLocation of access 
    byterefTypeTagKind of reference type. See JDWP.TypeTag 
    referenceTypeIDtypeIDType of field 
    fieldIDfieldIDField being accessed 
    tagged-objectIDobjectObject being accessed (null=0 for statics 
    Case FieldModification - if eventKind is JDWP.EventKind.FIELD_MODIFICATION: Notification of a field modification in the target VM.  
    intrequestIDRequest that generated event 
    threadIDthreadModifying thread 
    locationlocationLocation of modify 
    byterefTypeTagKind of reference type. See JDWP.TypeTag 
    referenceTypeIDtypeIDType of field 
    fieldIDfieldIDField being modified 
    tagged-objectIDobjectObject being modified (null=0 for statics 
    valuevalueToBeValue to be assigned 
    Case VMDeath - if eventKind is JDWP.EventKind.VM_DEATH:  
    intrequestIDRequest that generated event 

    Error Constants

    NONE0No error has occurred.  
    INVALID_THREAD10Passed thread is null, is not a valid thread or has exited.  
    INVALID_THREAD_GROUP11Thread group invalid.  
    INVALID_PRIORITY12Invalid priority.  
    THREAD_NOT_SUSPENDED13If the specified thread has not been suspended by an event.  
    THREAD_SUSPENDED14Thread already suspended.  
    INVALID_OBJECT20If this reference type has been unloaded and garbage collected.  
    INVALID_CLASS21Invalid class.  
    CLASS_NOT_PREPARED22Class has been loaded but not yet prepared.  
    INVALID_METHODID23Invalid method.  
    INVALID_LOCATION24Invalid location.  
    INVALID_FIELDID25Invalid field.  
    INVALID_FRAMEID30Invalid jframeID.  
    NO_MORE_FRAMES31There are no more Java or JNI frames on the call stack.  
    OPAQUE_FRAME32Information about the frame is not available.  
    NOT_CURRENT_FRAME33Operation can only be performed on current frame.  
    TYPE_MISMATCH34The variable is not an appropriate type for the function used.  
    INVALID_SLOT35Invalid slot.  
    DUPLICATE40Item already set.  
    NOT_FOUND41Desired element not found.  
    INVALID_MONITOR50Invalid monitor.  
    NOT_MONITOR_OWNER51This thread doesn't own the monitor.  
    INTERRUPT52The call has been interrupted before completion.  
    INVALID_CLASS_FORMAT60The virtual machine attempted to read a class file and determined that the file is malformed or otherwise cannot be interpreted as a class file.  
    CIRCULAR_CLASS_DEFINITION61A circularity has been detected while initializing a class.  
    FAILS_VERIFICATION62The verifier detected that a class file, though well formed, contained some sort of internal inconsistency or security problem.  
    ADD_METHOD_NOT_IMPLEMENTED63Adding methods has not been implemented.  
    SCHEMA_CHANGE_NOT_IMPLEMENTED64Schema change has not been implemented.  
    INVALID_TYPESTATE65The state of the thread has been modified, and is now inconsistent.  
    HIERARCHY_CHANGE_NOT_IMPLEMENTED66A direct superclass is different for the new class version, or the set of directly implemented interfaces is different and canUnrestrictedlyRedefineClasses is false.  
    DELETE_METHOD_NOT_IMPLEMENTED67The new class version does not declare a method declared in the old class version and canUnrestrictedlyRedefineClasses is false.  
    UNSUPPORTED_VERSION68A class file has a version number not supported by this VM.  
    NAMES_DONT_MATCH69The class name defined in the new class file is different from the name in the old class object.  
    CLASS_MODIFIERS_CHANGE_NOT_IMPLEMENTED70The new class version has different modifiers and and canUnrestrictedlyRedefineClasses is false.  
    METHOD_MODIFIERS_CHANGE_NOT_IMPLEMENTED71A method in the new class version has different modifiers than its counterpart in the old class version and and canUnrestrictedlyRedefineClasses is false.  
    NOT_IMPLEMENTED99The functionality is not implemented in this virtual machine.  
    NULL_POINTER100Invalid pointer.  
    ABSENT_INFORMATION101Desired information is not available.  
    INVALID_EVENT_TYPE102The specified event type id is not recognized.  
    ILLEGAL_ARGUMENT103Illegal argument.  
    OUT_OF_MEMORY110The function needed to allocate memory and no more memory was available for allocation.  
    ACCESS_DENIED111Debugging has not been enabled in this virtual machine. JVMDI cannot be used.  
    VM_DEAD112The virtual machine is not running.  
    INTERNAL113An unexpected internal error has occurred.  
    UNATTACHED_THREAD115The thread being used to call this function is not attached to the virtual machine. Calls must be made from attached threads.  
    INVALID_TAG500object type id or class tag.  
    ALREADY_INVOKING502Previous invoke not complete.  
    INVALID_INDEX503Index is invalid.  
    INVALID_LENGTH504The length is invalid.  
    INVALID_STRING506The string is invalid.  
    INVALID_CLASS_LOADER507The class loader is invalid.  
    INVALID_ARRAY508The array is invalid.  
    TRANSPORT_LOAD509Unable to load the transport.  
    TRANSPORT_INIT510Unable to initialize the transport.  
    NATIVE_METHOD511  
    INVALID_COUNT512The count is invalid.  

    EventKind Constants

    VM_DISCONNECTED100Never sent across JDWP  
    VM_STARTJDWP.EventKind.VM_INIT  
    THREAD_DEATHJDWP.EventKind.THREAD_END  
    SINGLE_STEP1  
    BREAKPOINT2  
    FRAME_POP3  
    EXCEPTION4  
    USER_DEFINED5  
    THREAD_START6  
    THREAD_END7  
    CLASS_PREPARE8  
    CLASS_UNLOAD9  
    CLASS_LOAD10  
    FIELD_ACCESS20  
    FIELD_MODIFICATION21  
    EXCEPTION_CATCH30  
    METHOD_ENTRY40  
    METHOD_EXIT41  
    VM_INIT90  
    VM_DEATH99  

    ThreadStatus Constants

    ZOMBIE0  
    RUNNING1  
    SLEEPING2  
    MONITOR3  
    WAIT4  

    SuspendStatus Constants

    SUSPEND_STATUS_SUSPENDED0x1  

    ClassStatus Constants

    VERIFIED1  
    PREPARED2  
    INITIALIZED4  
    ERROR8  

    TypeTag Constants

    CLASS1ReferenceType is a class.  
    INTERFACE2ReferenceType is an interface.  
    ARRAY3ReferenceType is an array.  

    Tag Constants

    ARRAY91'[' - an array object (objectID size).  
    BYTE66'B' - a byte value (1 byte).  
    CHAR67'C' - a character value (2 bytes).  
    OBJECT76'L' - an object (objectID size).  
    FLOAT70'F' - a float value (4 bytes).  
    DOUBLE68'D' - a double value (8 bytes).  
    INT73'I' - an int value (4 bytes).  
    LONG74'J' - a long value (8 bytes).  
    SHORT83'S' - a short value (2 bytes).  
    VOID86'V' - a void value (no bytes).  
    BOOLEAN90'Z' - a boolean value (1 byte).  
    STRING115's' - a String object (objectID size).  
    THREAD116't' - a Thread object (objectID size).  
    THREAD_GROUP103'g' - a ThreadGroup object (objectID size).  
    CLASS_LOADER108'l' - a ClassLoader object (objectID size).  
    CLASS_OBJECT99'c' - a class object object (objectID size).  

    StepDepth Constants

    INTO0Step into any method calls that occur before the end of the step.  
    OVER1Step over any method calls that occur before the end of the step.  
    OUT2Step out of the current method.  

    StepSize Constants

    MIN0Step by the minimum possible amount (often a bytecode instruction).  
    LINE1Step to the next source line unless there is no line number information in which case a MIN step is done instead.  

    SuspendPolicy Constants

    NONE0Suspend no threads when this event is encountered.  
    EVENT_THREAD1Suspend the event thread when this event is encountered.  
    ALL2Suspend all threads when this event is encountered.  

    InvokeOptions Constants

    INVOKE_SINGLE_THREADED0x01otherwise, all threads started.  
    INVOKE_NONVIRTUAL0x02otherwise, normal virtual invoke (instance methods only)  


    Copyright © 2003 Sun Microsystems, Inc. All Rights Reserved. 

    Please send comments to: java-debugger@java.sun.com 

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