- All Known Implementing Classes:
SimpleDoc
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 anjavax.print.attribute.DocAttributeSet
.
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
Modifier and TypeMethodDescriptionObtains the set of printing attributes for this doc object.Determines the doc flavor in which this doc object will supply its piece of print data.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.Obtains a reader for extracting character print data from this doc.Obtains an input stream for extracting byte print data from this doc.
-
Method Details
-
getDocFlavor
DocFlavor getDocFlavor()Determines the doc flavor in which this doc object will supply its piece of print data.- Returns:
- doc flavor
-
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. ThegetPrintData()
method returns an instance of the representation class whose name is given bygetDocFlavor()
.getRepresentationClassName()
, and the return value can be cast from classObject
to that representation class.- Returns:
- print data representation object
- Throws:
IOException
- 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 ifnull
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
Obtains a reader for extracting character print data from this doc. TheDoc
implementation is required to support this method if theDocFlavor
has one of the following print data representation classes, and returnnull
otherwise:- char[]
- java.lang.String
- java.io.Reader
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 aReader
, 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
- if there was an I/O error while creating the reader
-
getStreamForBytes
Obtains an input stream for extracting byte print data from this doc. TheDoc
implementation is required to support this method if theDocFlavor
has one of the following print data representation classes, and returnnull
otherwise:- byte[]
- java.io.InputStream
- 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
- if there was an I/O error while creating the input stream
-