Move gson to its own folder

[unical.git] / gson / com / google / gson / JsonSerializer.java

diff --git a/gson/com/google/gson/JsonSerializer.java b/gson/com/google/gson/JsonSerializer.java
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+++ b/gson/com/google/gson/JsonSerializer.java
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+/*
+ * 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)}.
+ *
+ * <p>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}.</p>
+ *
+ * <p><pre>
+ * public class Id&lt;T&gt; {
+ *   private final Class&lt;T&gt; clazz;
+ *   private final long value;
+ *
+ *   public Id(Class&lt;T&gt; clazz, long value) {
+ *     this.clazz = clazz;
+ *     this.value = value;
+ *   }
+ *
+ *   public long getValue() {
+ *     return value;
+ *   }
+ * }
+ * </pre></p>
+ *
+ * <p>The default serialization of {@code Id(com.foo.MyObject.class, 20L)} will be
+ * <code>{"clazz":com.foo.MyObject,"value":20}</code>. 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:</p>
+ *
+ * <p><pre>
+ * class IdSerializer implements JsonSerializer&lt;Id&gt;() {
+ *   public JsonElement serialize(Id id, Type typeOfId, JsonSerializationContext context) {
+ *     return new JsonPrimitive(id.getValue());
+ *   }
+ * }
+ * </pre></p>
+ *
+ * <p>You will also need to register {@code IdSerializer} with Gson as follows:</p>
+ * <pre>
+ * Gson gson = new GsonBuilder().registerTypeAdapter(Id.class, new IdSerializer()).create();
+ * </pre>
+ *
+ * <p>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 <T> type for which the serializer is being registered. It is possible that a serializer
+ *        may be asked to serialize a specific generic type of the T.
+ */
+public interface JsonSerializer<T> {
+
+  /**
+   * Gson invokes this call-back method during serialization when it encounters a field of the
+   * specified type.
+   *
+   * <p>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).</p>
+   *
+   * @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);
+}