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<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;
* }
* }
* </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<Id>() {
* 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);
}