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

     1  /*
     2   * Copyright (C) 2008 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;
    18  
    19  import java.lang.reflect.Type;
    20  
    21  /**
    22   * Interface representing a custom serializer for Json. You should write a custom serializer, if
    23   * you are not happy with the default serialization done by Gson. You will also need to register
    24   * this serializer through {@link GsonBuilder#registerTypeAdapter(Type, Object)}.
    25   *
    26   * <p>Let us look at example where defining a serializer will be useful. The {@code Id} class
    27   * defined below has two fields: {@code clazz} and {@code value}.</p>
    28   *
    29   * <p><pre>
    30   * public class Id&lt;T&gt; {
    31   *   private final Class&lt;T&gt; clazz;
    32   *   private final long value;
    33   *
    34   *   public Id(Class&lt;T&gt; clazz, long value) {
    35   *     this.clazz = clazz;
    36   *     this.value = value;
    37   *   }
    38   *
    39   *   public long getValue() {
    40   *     return value;
    41   *   }
    42   * }
    43   * </pre></p>
    44   *
    45   * <p>The default serialization of {@code Id(com.foo.MyObject.class, 20L)} will be
    46   * <code>{"clazz":com.foo.MyObject,"value":20}</code>. Suppose, you just want the output to be
    47   * the value instead, which is {@code 20} in this case. You can achieve that by writing a custom
    48   * serializer:</p>
    49   *
    50   * <p><pre>
    51   * class IdSerializer implements JsonSerializer&lt;Id&gt;() {
    52   *   public JsonElement serialize(Id id, Type typeOfId, JsonSerializationContext context) {
    53   *     return new JsonPrimitive(id.getValue());
    54   *   }
    55   * }
    56   * </pre></p>
    57   *
    58   * <p>You will also need to register {@code IdSerializer} with Gson as follows:</p>
    59   * <pre>
    60   * Gson gson = new GsonBuilder().registerTypeAdapter(Id.class, new IdSerializer()).create();
    61   * </pre>
    62   *
    63   * <p>New applications should prefer {@link TypeAdapter}, whose streaming API
    64   * is more efficient than this interface's tree API.
    65   *
    66   * @author Inderjeet Singh
    67   * @author Joel Leitch
    68   *
    69   * @param <T> type for which the serializer is being registered. It is possible that a serializer
    70   *        may be asked to serialize a specific generic type of the T.
    71   */
    72  public interface JsonSerializer<T> {
    73  
    74    /**
    75     * Gson invokes this call-back method during serialization when it encounters a field of the
    76     * specified type.
    77     *
    78     * <p>In the implementation of this call-back method, you should consider invoking
    79     * {@link JsonSerializationContext#serialize(Object, Type)} method to create JsonElements for any
    80     * non-trivial field of the {@code src} object. However, you should never invoke it on the
    81     * {@code src} object itself since that will cause an infinite loop (Gson will call your
    82     * call-back method again).</p>
    83     *
    84     * @param src the object that needs to be converted to Json.
    85     * @param typeOfSrc the actual type (fully genericized version) of the source object.
    86     * @return a JsonElement corresponding to the specified object.
    87     */
    88    public JsonElement serialize(T src, Type typeOfSrc, JsonSerializationContext context);
    89  }