| /* |
| * Copyright (c) 2000, 2017, 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 |
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| * questions. |
| */ |
| |
| package javax.print; |
| |
| import java.io.IOException; |
| |
| /** |
| * Interface {@code 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 {@code MultiDoc}, and the Print Job calls methods on |
| * that object to obtain the print data. |
| * <p> |
| * Interface {@code 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: |
| * |
| * <pre> |
| * void processMultiDoc(MultiDoc theMultiDoc) { |
| * |
| * MultiDoc current = theMultiDoc; |
| * |
| * while (current != null) { |
| * processDoc (current.getDoc()); |
| * current = current.next(); |
| * } |
| * } |
| * </pre> |
| * Of course, interface {@code MultiDoc} can be implemented in any way that |
| * fulfills the contract; it doesn't have to use a linked list in the |
| * implementation. |
| * <p> |
| * To get all the print data for a multidoc print job, a Print Service proxy |
| * could use either of two patterns: |
| * <ol type=1> |
| * <li>The <b>interleaved</b> 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.) |
| * <li>The <b>all-at-once</b> 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. |
| * </ol> |
| * 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. |
| * <p> |
| * 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 {@code MultiDoc} object using the |
| * interleaved pattern. That is, given a {@code MultiDoc} object, the print |
| * service proxy will call {@link #getDoc() getDoc()} one or more times until it |
| * successfully obtains the current {@code 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 {@code MultiDoc} |
| * object or an indication that there are no more. An implementation of |
| * interface {@code MultiDoc} can assume the print service proxy will follow |
| * this interleaved pattern; for any other pattern of usage, the |
| * {@code MultiDoc} implementation's behavior is unspecified. |
| * <p> |
| * 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 |
| * @throws IOException if an error occurred when 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 {@code null} |
| * if there are no further doc objects |
| * @throws IOException if an error occurred locating the next document |
| */ |
| public MultiDoc next() throws IOException; |
| } |