/* * Copyright (C) 2008 Google Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.google.gson; import java.lang.reflect.Type; /** * Interface representing a custom serializer for JSON. You should write a custom serializer, if you * are not happy with the default serialization done by Gson. You will also need to register this * serializer through {@link com.google.gson.GsonBuilder#registerTypeAdapter(Type, Object)}. * *
Let us look at example where defining a serializer will be useful. The {@code Id} class * defined below has two fields: {@code clazz} and {@code value}. * *
* public class Id<T> { * private final Class<T> clazz; * private final long value; * * public Id(Class<T> clazz, long value) { * this.clazz = clazz; * this.value = value; * } * * public long getValue() { * return value; * } * } ** *
The default serialization of {@code Id(com.foo.MyObject.class, 20L)} will be
* {"clazz":"com.foo.MyObject","value":20}
. Suppose, you just want the output to be the value
* instead, which is {@code 20} in this case. You can achieve that by writing a custom serializer:
*
*
* class IdSerializer implements JsonSerializer<Id> { * public JsonElement serialize(Id id, Type typeOfId, JsonSerializationContext context) { * return new JsonPrimitive(id.getValue()); * } * } ** *
You will also need to register {@code IdSerializer} with Gson as follows: * *
* Gson gson = new GsonBuilder().registerTypeAdapter(Id.class, new IdSerializer()).create(); ** *
Serializers should be stateless and thread-safe, otherwise the thread-safety guarantees of * {@link Gson} might not apply. * *
New applications should prefer {@link TypeAdapter}, whose streaming API is more efficient than
* this interface's tree API.
*
* @author Inderjeet Singh
* @author Joel Leitch
* @param In the implementation of this call-back method, you should consider invoking {@link
* JsonSerializationContext#serialize(Object, Type)} method to create JsonElements for any
* non-trivial field of the {@code src} object. However, you should never invoke it on the {@code
* src} object itself since that will cause an infinite loop (Gson will call your call-back method
* again).
*
* @param src the object that needs to be converted to Json.
* @param typeOfSrc the actual type (fully genericized version) of the source object.
* @return a JsonElement corresponding to the specified object.
*/
public JsonElement serialize(T src, Type typeOfSrc, JsonSerializationContext context);
}