github.com/keysonZZZ/kmg@v0.0.0-20151121023212-05317bfd7d39/kmgRpc/kmgRpcJava/java/src/com/google/gson/annotations/JsonAdapter.java (about)

     1  /*
     2   * Copyright (C) 2014 Google Inc.
     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  
    17  package com.google.gson.annotations;
    18  
    19  import com.google.gson.TypeAdapter;
    20  import com.google.gson.TypeAdapterFactory;
    21  import java.lang.annotation.ElementType;
    22  import java.lang.annotation.Retention;
    23  import java.lang.annotation.RetentionPolicy;
    24  import java.lang.annotation.Target;
    25  
    26  /**
    27   * An annotation that indicates the Gson {@link TypeAdapter} to use with a class
    28   * or field.
    29   *
    30   * <p>Here is an example of how this annotation is used:</p>
    31   * <pre>
    32   * &#64JsonAdapter(UserJsonAdapter.class)
    33   * public class User {
    34   *   public final String firstName, lastName;
    35   *   private User(String firstName, String lastName) {
    36   *     this.firstName = firstName;
    37   *     this.lastName = lastName;
    38   *   }
    39   * }
    40   * public class UserJsonAdapter extends TypeAdapter&lt;User&gt; {
    41   *   &#64Override public void write(JsonWriter out, User user) throws IOException {
    42   *     // implement write: combine firstName and lastName into name
    43   *     out.beginObject();
    44   *     out.name("name");
    45   *     out.value(user.firstName + " " + user.lastName);
    46   *     out.endObject();
    47   *     // implement the write method
    48   *   }
    49   *   &#64Override public User read(JsonReader in) throws IOException {
    50   *     // implement read: split name into firstName and lastName
    51   *     in.beginObject();
    52   *     in.nextName();
    53   *     String[] nameParts = in.nextString().split(" ");
    54   *     in.endObject();
    55   *     return new User(nameParts[0], nameParts[1]);
    56   *   }
    57   * }
    58   * </pre>
    59   *
    60   * Since User class specified UserJsonAdapter.class in &#64JsonAdapter annotation, it
    61   * will automatically be invoked to serialize/deserialize User instances. <br>
    62   *
    63   * <p> Here is an example of how to apply this annotation to a field.
    64   * <pre>
    65   * private static final class Gadget {
    66   *   &#64JsonAdapter(UserJsonAdapter2.class)
    67   *   final User user;
    68   *   Gadget(User user) {
    69   *     this.user = user;
    70   *   }
    71   * }
    72   * </pre>
    73   *
    74   * It's possible to specify different type adapters on a field, that
    75   * field's type, and in the {@link com.google.gson.GsonBuilder}. Field
    76   * annotations take precedence over {@code GsonBuilder}-registered type
    77   * adapters, which in turn take precedence over annotated types.
    78   *
    79   * <p>The class referenced by this annotation must be either a {@link
    80   * TypeAdapter} or a {@link TypeAdapterFactory}. Using the factory interface
    81   * makes it possible to delegate to the enclosing {@code Gson} instance.
    82   *
    83   * @since 2.3
    84   *
    85   * @author Inderjeet Singh
    86   * @author Joel Leitch
    87   * @author Jesse Wilson
    88   */
    89  // Note that the above example is taken from AdaptAnnotationTest.
    90  @Retention(RetentionPolicy.RUNTIME)
    91  @Target({ElementType.TYPE, ElementType.FIELD})
    92  public @interface JsonAdapter {
    93  
    94    /** Either a {@link TypeAdapter} or {@link TypeAdapterFactory}. */
    95    Class<?> value();
    96  
    97  }