1/*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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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).
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24 */
25
26package javax.print;
27
28import 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 *
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
111public 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}
137