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