001/*
002 * Copyright (C) 2009 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.annotations;
018
019import java.lang.annotation.Documented;
020import java.lang.annotation.ElementType;
021import java.lang.annotation.Retention;
022import java.lang.annotation.RetentionPolicy;
023import java.lang.annotation.Target;
024
025/**
026 * The presence of this annotation on a type indicates that the type may be
027 * used with the
028 * <a href="http://code.google.com/webtoolkit/">Google Web Toolkit</a> (GWT).
029 * When applied to a method, the return type of the method is GWT compatible.
030 * It's useful to indicate that an instance created by factory methods has a GWT
031 * serializable type.  In the following example,
032 *
033 * <pre style="code">
034 * {@literal @}GwtCompatible
035 * class Lists {
036 *   ...
037 *   {@literal @}GwtCompatible(serializable = true)
038 *   static &lt;E> List&lt;E> newArrayList(E... elements) {
039 *     ...
040 *   }
041 * }
042 * </pre>
043 * <p>The return value of {@code Lists.newArrayList(E[])} has GWT
044 * serializable type.  It is also useful in specifying contracts of interface
045 * methods.  In the following example,
046 *
047 * <pre style="code">
048 * {@literal @}GwtCompatible
049 * interface ListFactory {
050 *   ...
051 *   {@literal @}GwtCompatible(serializable = true)
052 *   &lt;E> List&lt;E> newArrayList(E... elements);
053 * }
054 * </pre>
055 * <p>The {@code newArrayList(E[])} method of all implementations of {@code
056 * ListFactory} is expected to return a value with a GWT serializable type.
057 *
058 * <p>Note that a {@code GwtCompatible} type may have some {@link
059 * GwtIncompatible} methods.
060 *
061 * @author Charles Fry
062 * @author Hayward Chan
063 */
064@Retention(RetentionPolicy.CLASS)
065@Target({ ElementType.TYPE, ElementType.METHOD })
066@Documented
067@GwtCompatible
068public @interface GwtCompatible {
069
070  /**
071   * When {@code true}, the annotated type or the type of the method return
072   * value is GWT serializable.
073   *
074   * @see <a href="http://code.google.com/webtoolkit/doc/latest/DevGuideServerCommunication.html#DevGuideSerializableTypes">
075   *     Documentation about GWT serialization</a>
076   */
077  boolean serializable() default false;
078
079  /**
080   * When {@code true}, the annotated type is emulated in GWT. The emulated
081   * source (also known as super-source) is different from the implementation
082   * used by the JVM.
083   *
084   * @see <a href="http://code.google.com/webtoolkit/doc/latest/DevGuideOrganizingProjects.html#DevGuideModules">
085   *     Documentation about GWT emulated source</a>
086   */
087  boolean emulated() default false;
088}