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    
017    package com.google.common.annotations;
018    
019    import java.lang.annotation.Documented;
020    import java.lang.annotation.ElementType;
021    import java.lang.annotation.Retention;
022    import java.lang.annotation.RetentionPolicy;
023    import 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     * 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     * 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
068    public @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    }