GwtCompatible.java revision 1d580d0f6ee4f21eb309ba7b509d2c6d671c4044 
1/*
2 * Copyright (C) 2009 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.common.annotations;
18
19import java.lang.annotation.Documented;
20import java.lang.annotation.ElementType;
21import java.lang.annotation.Retention;
22import java.lang.annotation.RetentionPolicy;
23import java.lang.annotation.Target;
24
25/**
26 * The presence of this annotation on a type indicates that the type may be
27 * used with the
28 * <a href="http://code.google.com/webtoolkit/">Google Web Toolkit</a> (GWT).
29 * When applied to a method, the return type of the method is GWT compatible.
30 * It's useful to indicate that an instance created by factory methods has a GWT
31 * serializable type.  In the following example,
32 *
33 * <pre style="code">
34 * {@literal @}GwtCompatible
35 * class Lists {
36 *   ...
37 *   {@literal @}GwtCompatible(serializable = true)
38 *   static &lt;E> List&lt;E> newArrayList(E... elements) {
39 *     ...
40 *   }
41 * }
42 * </pre>
43 * The return value of {@code Lists.newArrayList(E[])} has GWT
44 * serializable type.  It is also useful in specifying contracts of interface
45 * methods.  In the following example,
46 *
47 * <pre style="code">
48 * {@literal @}GwtCompatible
49 * interface ListFactory {
50 *   ...
51 *   {@literal @}GwtCompatible(serializable = true)
52 *   &lt;E> List&lt;E> newArrayList(E... elements);
53 * }
54 * </pre>
55 * The {@code newArrayList(E[])} method of all implementations of {@code
56 * ListFactory} is expected to return a value with a GWT serializable type.
57 *
58 * <p>Note that a {@code GwtCompatible} type may have some {@link
59 * GwtIncompatible} methods.
60 *
61 * @author Charles Fry
62 * @author Hayward Chan
63 */
64@Retention(RetentionPolicy.CLASS)
65@Target({ ElementType.TYPE, ElementType.METHOD })
66@Documented
67@GwtCompatible
68public @interface GwtCompatible {
69
70  /**
71   * When {@code true}, the annotated type or the type of the method return
72   * value is GWT serializable.
73   *
74   * @see <a href="http://code.google.com/webtoolkit/doc/latest/DevGuideServerCommunication.html#DevGuideSerializableTypes">
75   *     Documentation about GWT serialization</a>
76   */
77  boolean serializable() default false;
78
79  /**
80   * When {@code true}, the annotated type is emulated in GWT. The emulated
81   * source (also known as super-source) is different from the implementation
82   * used by the JVM.
83   *
84   * @see <a href="http://code.google.com/webtoolkit/doc/latest/DevGuideOrganizingProjects.html#DevGuideModules">
85   *     Documentation about GWT emulated source</a>
86   */
87  boolean emulated() default false;
88}
89