1 /*
2 * Copyright 2005-2006 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package javax.xml.bind.annotation.adapters;
27
28 import javax.xml.bind.Unmarshaller;
29 import javax.xml.bind.Marshaller;
30
31 /**
32 * Adapts a Java type for custom marshaling.
33 *
34 * <p> <b> Usage: </b> </p>
35 *
36 * <p>
37 * Some Java types do not map naturally to a XML representation, for
38 * example <tt>HashMap</tt> or other non JavaBean classes. Conversely,
39 * a XML repsentation may map to a Java type but an application may
40 * choose to accesss the XML representation using another Java
41 * type. For example, the schema to Java binding rules bind
42 * xs:DateTime by default to XmlGregorianCalendar. But an application
43 * may desire to bind xs:DateTime to a custom type,
44 * MyXmlGregorianCalendar, for example. In both cases, there is a
45 * mismatch between <i> bound type </i>, used by an application to
46 * access XML content and the <i> value type</i>, that is mapped to an
47 * XML representation.
48 *
49 * <p>
50 * This abstract class defines methods for adapting a bound type to a value
51 * type or vice versa. The methods are invoked by the JAXB binding
52 * framework during marshaling and unmarshalling:
53 *
54 * <ul>
55 * <li> <b> XmlAdapter.marshal(...): </b> During marshalling, JAXB
56 * binding framework invokes XmlAdapter.marshal(..) to adapt a
57 * bound type to value type, which is then marshaled to XML
58 * representation. </li>
59 *
60 * <li> <b> XmlAdapter.unmarshal(...): </b> During unmarshalling,
61 * JAXB binding framework first unmarshals XML representation
62 * to a value type and then invokes XmlAdapter.unmarshal(..) to
63 * adapt the value type to a bound type. </li>
64 * </ul>
65 *
66 * Writing an adapter therefore involves the following steps:
67 *
68 * <ul>
69 * <li> Write an adapter that implements this abstract class. </li>
70 * <li> Install the adapter using the annotation {@link
71 * XmlJavaTypeAdapter} </li>
72 * </ul>
73 *
74 * <p><b>Example:</b> Customized mapping of <tt>HashMap</tt></p>
75 * <p> The following example illustrates the use of
76 * <tt>@XmlAdapter</tt> and <tt>@XmlJavaTypeAdapter</tt> to
77 * customize the mapping of a <tt>HashMap</tt>.
78 *
79 * <p> <b> Step 1: </b> Determine the desired XML representation for HashMap.
80 *
81 * <pre>
82 * <hashmap>
83 * <entry key="id123">this is a value</entry>
84 * <entry key="id312">this is another value</entry>
85 * ...
86 * </hashmap>
87 * </pre>
88 *
89 * <p> <b> Step 2: </b> Determine the schema definition that the
90 * desired XML representation shown above should follow.
91 *
92 * <pre>
93 *
94 * <xs:complexType name="myHashMapType">
95 * <xs:sequence>
96 * <xs:element name="entry" type="myHashMapEntryType"
97 * minOccurs = "0" maxOccurs="unbounded"/>
98 * </xs:sequence>
99 * </xs:complexType>
100 *
101 * <xs:complexType name="myHashMapEntryType">
102 * <xs:simpleContent>
103 * <xs:extension base="xs:string">
104 * <xs:attribute name="key" type="xs:int"/>
105 * </xs:extension>
106 * </xs:simpleContent>
107 * </xs:complexType>
108 *
109 * </pre>
110 *
111 * <p> <b> Step 3: </b> Write value types that can generate the above
112 * schema definition.
113 *
114 * <pre>
115 * public class MyHashMapType {
116 * List<MyHashMapEntryType> entry;
117 * }
118 *
119 * public class MyHashMapEntryType {
120 * @XmlAttribute
121 * public Integer key;
122 *
123 * @XmlValue
124 * public String value;
125 * }
126 * </pre>
127 *
128 * <p> <b> Step 4: </b> Write the adapter that adapts the value type,
129 * MyHashMapType to a bound type, HashMap, used by the application.
130 *
131 * <pre>
132 * public final class MyHashMapAdapter extends
133 * XmlAdapter<HashMap, MyHashMapType> { ... }
134 *
135 * </pre>
136 *
137 * <p> <b> Step 5: </b> Use the adapter.
138 *
139 * <pre>
140 * public class Foo {
141 * @XmlJavaTypeAdapter(MyHashMapAdapter.class)
142 * HashMap hashmap;
143 * ...
144 * }
145 * </pre>
146 *
147 * The above code fragment will map to the following schema:
148 *
149 * <pre>
150 * <xs:complexType name="Foo">
151 * <xs:sequence>
152 * <xs:element name="hashmap" type="myHashMapType"
153 * </xs:sequence>
154 * </xs:complexType>
155 * </pre>
156 *
157 * @param <BoundType>
158 * The type that JAXB doesn't know how to handle. An adapter is written
159 * to allow this type to be used as an in-memory representation through
160 * the <tt>ValueType</tt>.
161 * @param <ValueType>
162 * The type that JAXB knows how to handle out of the box.
163 *
164 * @author <ul><li>Sekhar Vajjhala, Sun Microsystems Inc.</li> <li> Kohsuke Kawaguchi, Sun Microsystems Inc.</li></ul>
165 * @see XmlJavaTypeAdapter
166 * @since JAXB 2.0
167 */
168 public abstract class XmlAdapter<ValueType,BoundType> {
169
170 /**
171 * Do-nothing constructor for the derived classes.
172 */
173 protected XmlAdapter() {}
174
175 /**
176 * Convert a value type to a bound type.
177 *
178 * @param v
179 * The value to be converted. Can be null.
180 * @throws Exception
181 * if there's an error during the conversion. The caller is responsible for
182 * reporting the error to the user through {@link javax.xml.bind.ValidationEventHandler}.
183 */
184 public abstract BoundType unmarshal(ValueType v) throws Exception;
185
186 /**
187 * Convert a bound type to a value type.
188 *
189 * @param v
190 * The value to be convereted. Can be null.
191 * @throws Exception
192 * if there's an error during the conversion. The caller is responsible for
193 * reporting the error to the user through {@link javax.xml.bind.ValidationEventHandler}.
194 */
195 public abstract ValueType marshal(BoundType v) throws Exception;
196 }
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