JavaTM 2 Platform Std. Ed. v1.6.0
javax.print
Interface Doc
- All Known Implementing Classes:
- SimpleDoc
public interface Doc
Interface Doc specifies the interface for an object that supplies one piece
of print data for a Print Job. "Doc" is a short, easy-to-pronounce term
that means "a piece of print data." The client passes to the Print Job an
object that implements interface Doc, and the Print Job calls methods on
that object to obtain the print data. The Doc interface lets a Print Job:
-
Determine the format, or "doc flavor" (class
DocFlavor ),
in which the print data is available. A doc flavor designates the print
data format (a MIME type) and the representation class of the object
from which the print data comes.
-
Obtain the print data representation object, which is an instance of the
doc flavor's representation class. The Print Job can then obtain the actual
print data from the representation object.
-
Obtain the printing attributes that specify additional characteristics of
the doc or that specify processing instructions to be applied to the doc.
Printing attributes are defined in package
javax.print.attribute . The doc returns its printing attributes stored in
an javax.print.attribute.DocAttributeSet .
Each method in an implementation of interface Doc is permitted always to
return the same object each time the method is called.
This has implications
for a Print Job or other caller of a doc object whose print data
representation object "consumes" the print data as the caller obtains the
print data, such as a print data representation object which is a stream.
Once the Print Job has called getPrintData() and obtained the stream, any further calls to
getPrintData() will return the same
stream object upon which reading may already be in progress, not a new
stream object that will re-read the print data from the beginning. Specifying
a doc object to behave this way simplifies the implementation of doc objects,
and is justified on the grounds that a particular doc is intended to convey
print data only to one Print Job, not to several different Print Jobs. (To
convey the same print data to several different Print Jobs, you have to
create several different doc objects on top of the same print data source.)
Interface Doc affords considerable implementation flexibility. The print data
might already be in existence when the doc object is constructed. In this
case the objects returned by the doc's methods can be supplied to the doc's
constructor, be stored in the doc ahead of time, and simply be returned when
called for. Alternatively, the print data might not exist yet when the doc
object is constructed. In this case the doc object might provide a "lazy"
implementation that generates the print data representation object (and/or
the print data) only when the Print Job calls for it (when the Print Job
calls the getPrintData() method).
There is no restriction on the number of client threads that may be
simultaneously accessing the same doc. Therefore, all implementations of
interface Doc must be designed to be multiple thread safe.
However there can only be one consumer of the print data obtained from a
Doc.
If print data is obtained from the client as a stream, by calling Doc's
getReaderForText() or getStreamForBytes()
methods, or because the print data source is already an InputStream or
Reader, then the print service should always close these streams for the
client on all job completion conditions. With the following caveat.
If the print data is itself a stream, the service will always close it.
If the print data is otherwise something that can be requested as a stream,
the service will only close the stream if it has obtained the stream before
terminating. That is, just because a print service might request data as
a stream does not mean that it will, with the implications that Doc
implementors which rely on the service to close them should create such
streams only in response to a request from the service.
Method Summary |
DocAttributeSet |
getAttributes()
Obtains the set of printing attributes for this doc object. |
DocFlavor |
getDocFlavor()
Determines the doc flavor in which this doc object will supply its
piece of print data. |
Object |
getPrintData()
Obtains the print data representation object that contains this doc
object's piece of print data in the format corresponding to the
supported doc flavor. |
Reader |
getReaderForText()
Obtains a reader for extracting character print data from this doc. |
InputStream |
getStreamForBytes()
Obtains an input stream for extracting byte print data from this
doc. |
getDocFlavor
DocFlavor getDocFlavor()
- Determines the doc flavor in which this doc object will supply its
piece of print data.
- Returns:
- Doc flavor.
getPrintData
Object getPrintData()
throws IOException
- Obtains the print data representation object that contains this doc
object's piece of print data in the format corresponding to the
supported doc flavor.
The
getPrintData() method returns an instance of
the representation class whose name is given by getDocFlavor() .getRepresentationClassName() , and the return value can be cast
from class Object to that representation class.
- Returns:
- Print data representation object.
- Throws:
IOException - Thrown if the representation class is a stream and there was an I/O
error while constructing the stream.
getAttributes
DocAttributeSet getAttributes()
- Obtains the set of printing attributes for this doc object. If the
returned attribute set includes an instance of a particular attribute
X, the printer must use that attribute value for this doc,
overriding any value of attribute X in the job's attribute set.
If the returned attribute set does not include an instance
of a particular attribute X or if null is returned, the printer
must consult the job's attribute set to obtain the value for
attribute X, and if not found there, the printer must use an
implementation-dependent default value. The returned attribute set is
unmodifiable.
- Returns:
- Unmodifiable set of printing attributes for this doc, or null
to obtain all attribute values from the job's attribute
set.
getReaderForText
Reader getReaderForText()
throws IOException
- Obtains a reader for extracting character print data from this doc.
The Doc implementation is required to support this method if the
DocFlavor has one of the following print data representation classes,
and return null otherwise:
- char[]
- java.lang.String
- java.io.Reader
The doc's print data representation object is used to construct and
return a Reader for reading the print data as a stream of characters
from the print data representation object.
However, if the print data representation object is itself a Reader,
then the print data representation object is simply returned.
- Returns:
- Reader for reading the print data characters from this doc.
If a reader cannot be provided because this doc does not meet
the criteria stated above, null is returned.
- Throws:
IOException - Thrown if there was an I/O error while creating the reader.
getStreamForBytes
InputStream getStreamForBytes()
throws IOException
- Obtains an input stream for extracting byte print data from this
doc. The Doc implementation is required to support this method if
the DocFlavor has one of the following print data representation
classes, and return null otherwise:
- byte[]
- java.io.InputStream
This doc's print data representation object is obtained, then an input
stream for reading the print data from the print data representation
object as a stream of bytes is created and returned. However, if the
print data representation object is itself an input stream, then the
print data representation object is simply returned.
- Returns:
- Input stream for reading the print data bytes from this doc. If
an input stream cannot be provided because this doc does not
meet the criteria stated above, null is returned.
- Throws:
IOException - Thrown if there was an I/O error while creating the input stream.
Copyright 2003 Sun Microsystems, Inc. All rights reserved
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