/* * Copyright (c) 2000, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package javax.print; import java.io.IOException; /** * Interface MultiDoc specifies the interface for an object that supplies more * than one piece of print data for a Print Job. "Doc" is a short, * easy-to-pronounce term that means "a piece of print data," and a "multidoc" * is a group of several docs. The client passes to the Print Job an object * that implements interface MultiDoc, and the Print Job calls methods on * that object to obtain the print data. *

* Interface MultiDoc provides an abstraction similar to a "linked list" of * docs. A multidoc object is like a node in the linked list, containing the * current doc in the list and a pointer to the next node (multidoc) in the * list. The Print Job can call the multidoc's {@link #getDoc() * getDoc()} method to get the current doc. When it's ready to go * on to the next doc, the Print Job can call the multidoc's {@link #next() * next()} method to get the next multidoc, which contains the * next doc. So Print Job code for accessing a multidoc might look like this: * 

 *      void processMultiDoc(MultiDoc theMultiDoc) {
 *
 *          MultiDoc current = theMultiDoc;

 *          while (current != null) {
 *              processDoc (current.getDoc());
 *              current = current.next();
 *          }
 *      }
 *
*

* Of course, interface MultiDoc can be implemented in any way that fulfills * the contract; it doesn't have to use a linked list in the implementation. *

* To get all the print data for a multidoc print job, a Print Service * proxy could use either of two patterns: *

    *
  1. * The interleaved pattern: Get the doc from the current multidoc. Get * the print data representation object from the current doc. Get all the print * data from the print data representation object. Get the next multidoc from * the current multidoc, and repeat until there are no more. (The code example * above uses the interleaved pattern.) *

    *

  2. * The all-at-once pattern: Get the doc from the current multidoc, and * save the doc in a list. Get the next multidoc from the current multidoc, and * repeat until there are no more. Then iterate over the list of saved docs. Get * the print data representation object from the current doc. Get all the print * data from the print data representation object. Go to the next doc in the * list, and repeat until there are no more. *
* Now, consider a printing client that is generating print data on the fly and * does not have the resources to store more than one piece of print data at a * time. If the print service proxy used the all-at-once pattern to get the * print data, it would pose a problem for such a client; the client would have * to keep all the docs' print data around until the print service proxy comes * back and asks for them, which the client is not able to do. To work with such * a client, the print service proxy must use the interleaved pattern. *

* To address this problem, and to simplify the design of clients providing * multiple docs to a Print Job, every Print Service proxy that supports * multidoc print jobs is required to access a MultiDoc object using the * interleaved pattern. That is, given a MultiDoc object, the print service * proxy will call {@link #getDoc() getDoc()} one or more times * until it successfully obtains the current Doc object. The print service proxy * will then obtain the current doc's print data, not proceeding until all the * print data is obtained or an unrecoverable error occurs. If it is able to * continue, the print service proxy will then call {@link #next() * next()} one or more times until it successfully obtains either * the next MultiDoc object or an indication that there are no more. An * implementation of interface MultiDoc can assume the print service proxy will * follow this interleaved pattern; for any other pattern of usage, the MultiDoc * implementation's behavior is unspecified. *

* There is no restriction on the number of client threads that may be * simultaneously accessing the same multidoc. Therefore, all implementations of * interface MultiDoc must be designed to be multiple thread safe. In fact, a * client thread could be adding docs to the end of the (conceptual) list while * a Print Job thread is simultaneously obtaining docs from the beginning of the * list; provided the multidoc object synchronizes the threads properly, the two * threads will not interfere with each other */ public interface MultiDoc { /** * Obtain the current doc object. * * @return Current doc object. * * @exception IOException * Thrown if a error ocurred reading the document. */ public Doc getDoc() throws IOException; /** * Go to the multidoc object that contains the next doc object in the * sequence of doc objects. * * @return Multidoc object containing the next doc object, or null if * there are no further doc objects. * * @exception IOException * Thrown if an error occurred locating the next document */ public MultiDoc next() throws IOException; }