/*
* @(#)Doc.java 1.7 03/12/19
*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package javax.print;
import java.io.InputStream;
import java.io.IOException;
import java.io.Reader;
import java.io.UnsupportedEncodingException;
import javax.print.attribute.AttributeSet;
import javax.print.attribute.DocAttributeSet;
/**
* 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:
* <UL>
* <LI>
* Determine the format, or "doc flavor" (class {@link DocFlavor 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.
* <P>
* <LI>
* 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.
* <P>
* <LI>
* 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 {@link javax.print.attribute
* javax.print.attribute}. The doc returns its printing attributes stored in
* an {@link javax.print.attribute.DocAttributeSet javax.print.attribute.DocAttributeSet}.
* </UL>
* <P>
* 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 {@link #getPrintData()
* <CODE>getPrintData()</CODE>} and obtained the stream, any further calls to
* {@link #getPrintData() <CODE>getPrintData()</CODE>} will return the same
* stream object upon which reading may already be in progress, <I>not</I> 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.)
* <P>
* 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 {@link #getPrintData() <CODE>getPrintData()</CODE>} method).
* <P>
* 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.
* <p>
* However there can only be one consumer of the print data obtained from a
* Doc.
* <p>
* If print data is obtained from the client as a stream, by calling Doc's
* <code>getReaderForText()</code> or <code>getStreamForBytes()</code>
* 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.
* <P>
* <HR>
*/
public interface Doc {
/**
* Determines the doc flavor in which this doc object will supply its
* piece of print data.
*
* @return Doc flavor.
*/
public DocFlavor getDocFlavor();
/**
* 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 <CODE>getPrintData()</CODE> method returns an instance of
* the representation class whose name is given by <CODE>{@link
* #getDocFlavor() getDocFlavor()}.{@link
* DocFlavor#getRepresentationClassName()
* getRepresentationClassName()}</CODE>, and the return value can be cast
* from class Object to that representation class.
*
* @return Print data representation object.
*
* @exception IOException
* Thrown if the representation class is a stream and there was an I/O
* error while constructing the stream.
*/
public Object getPrintData() throws IOException;
/**
* Obtains the set of printing attributes for this doc object. If the
* returned attribute set includes an instance of a particular attribute
* <I>X,</I> the printer must use that attribute value for this doc,
* overriding any value of attribute <I>X</I> in the job's attribute set.
* If the returned attribute set does not include an instance
* of a particular attribute <I>X</I> or if null is returned, the printer
* must consult the job's attribute set to obtain the value for
* attribute <I>X,</I> and if not found there, the printer must use an
* implementation-dependent default value. The returned attribute set is
* unmodifiable.
*
* @return Unmodifiable set of printing attributes for this doc, or null
* to obtain all attribute values from the job's attribute
* set.
*/
public DocAttributeSet getAttributes();
/**
* 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:
* <UL>
* <LI> char[]
* <LI> java.lang.String
* <LI> java.io.Reader
* </UL>
* 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.
* <P>
* @return 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.
*
* @exception IOException
* Thrown if there was an I/O error while creating the reader.
*/
public Reader getReaderForText() 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:
* <UL>
* <LI> byte[]
* <LI> java.io.InputStream
* </UL>
* 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.
* <P>
* @return 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.
*
* @exception IOException
* Thrown if there was an I/O error while creating the input stream.
*/
public InputStream getStreamForBytes() throws IOException;
}
|
