1 /*
2 * Copyright (c) 2000, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package javax.print;
27
28 import java.io.IOException;
29
30 /**
31 * Interface MultiDoc specifies the interface for an object that supplies more
32 * than one piece of print data for a Print Job. "Doc" is a short,
33 * easy-to-pronounce term that means "a piece of print data," and a "multidoc"
34 * is a group of several docs. The client passes to the Print Job an object
35 * that implements interface MultiDoc, and the Print Job calls methods on
36 * that object to obtain the print data.
37 * <P>
38 * Interface MultiDoc provides an abstraction similar to a "linked list" of
39 * docs. A multidoc object is like a node in the linked list, containing the
40 * current doc in the list and a pointer to the next node (multidoc) in the
41 * list. The Print Job can call the multidoc's {@link #getDoc()
42 * getDoc()} method to get the current doc. When it's ready to go
43 * on to the next doc, the Print Job can call the multidoc's {@link #next()
44 * next()} method to get the next multidoc, which contains the
45 * next doc. So Print Job code for accessing a multidoc might look like this:
46 * <PRE>
47 * void processMultiDoc(MultiDoc theMultiDoc) {
48 *
49 * MultiDoc current = theMultiDoc;
50
51 * while (current != null) {
52 * processDoc (current.getDoc());
53 * current = current.next();
54 * }
55 * }
56 * </PRE>
57 * <P>
58 * Of course, interface MultiDoc can be implemented in any way that fulfills
59 * the contract; it doesn't have to use a linked list in the implementation.
60 * <P>
61 * To get all the print data for a multidoc print job, a Print Service
62 * proxy could use either of two patterns:
63 * <OL TYPE=1>
64 * <LI>
65 * The <B>interleaved</B> pattern: Get the doc from the current multidoc. Get
66 * the print data representation object from the current doc. Get all the print
67 * data from the print data representation object. Get the next multidoc from
68 * the current multidoc, and repeat until there are no more. (The code example
69 * above uses the interleaved pattern.)
70 * <P>
71 * <LI>
72 * The <B>all-at-once</B> pattern: Get the doc from the current multidoc, and
73 * save the doc in a list. Get the next multidoc from the current multidoc, and
74 * repeat until there are no more. Then iterate over the list of saved docs. Get
75 * the print data representation object from the current doc. Get all the print
76 * data from the print data representation object. Go to the next doc in the
77 * list, and repeat until there are no more.
78 * </OL>
79 * Now, consider a printing client that is generating print data on the fly and
80 * does not have the resources to store more than one piece of print data at a
81 * time. If the print service proxy used the all-at-once pattern to get the
82 * print data, it would pose a problem for such a client; the client would have
83 * to keep all the docs' print data around until the print service proxy comes
84 * back and asks for them, which the client is not able to do. To work with such
85 * a client, the print service proxy must use the interleaved pattern.
86 * <P>
87 * To address this problem, and to simplify the design of clients providing
88 * multiple docs to a Print Job, every Print Service proxy that supports
89 * multidoc print jobs is required to access a MultiDoc object using the
90 * interleaved pattern. That is, given a MultiDoc object, the print service
91 * proxy will call {@link #getDoc() getDoc()} one or more times
92 * until it successfully obtains the current Doc object. The print service proxy
93 * will then obtain the current doc's print data, not proceeding until all the
94 * print data is obtained or an unrecoverable error occurs. If it is able to
95 * continue, the print service proxy will then call {@link #next()
96 * next()} one or more times until it successfully obtains either
97 * the next MultiDoc object or an indication that there are no more. An
98 * implementation of interface MultiDoc can assume the print service proxy will
99 * follow this interleaved pattern; for any other pattern of usage, the MultiDoc
100 * implementation's behavior is unspecified.
101 * <P>
102 * There is no restriction on the number of client threads that may be
103 * simultaneously accessing the same multidoc. Therefore, all implementations of
104 * interface MultiDoc must be designed to be multiple thread safe. In fact, a
105 * client thread could be adding docs to the end of the (conceptual) list while
106 * a Print Job thread is simultaneously obtaining docs from the beginning of the
107 * list; provided the multidoc object synchronizes the threads properly, the two
108 * threads will not interfere with each other
109 */
110
111 public interface MultiDoc {
112
113
114 /**
115 * Obtain the current doc object.
116 *
117 * @return Current doc object.
118 *
119 * @exception IOException
120 * Thrown if a error occurred reading the document.
121 */
122 public Doc getDoc() throws IOException;
123
124 /**
125 * Go to the multidoc object that contains the next doc object in the
126 * sequence of doc objects.
127 *
128 * @return Multidoc object containing the next doc object, or null if
129 * there are no further doc objects.
130 *
131 * @exception IOException
132 * Thrown if an error occurred locating the next document
133 */
134 public MultiDoc next() throws IOException;
135
136 }