public interface

JsonSerializer

com.google.gson.JsonSerializer<T>

Class Overview

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 registerTypeAdapter(Type, Object).

Let us look at example where defining a serializer will be useful. The Id class defined below has two fields: clazz and 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 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 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 IdSerializer with Gson as follows:

 Gson gson = new GsonBuilder().registerTypeAdapter(Id.class, new IdSerializer()).create();
 

New applications should prefer TypeAdapter, whose streaming API is more efficient than this interface's tree API.

Summary

Public Methods
abstract JsonElement serialize(T src, Type typeOfSrc, JsonSerializationContext context)
Gson invokes this call-back method during serialization when it encounters a field of the specified type.

Public Methods

public abstract JsonElement serialize (T src, Type typeOfSrc, JsonSerializationContext context)

Gson invokes this call-back method during serialization when it encounters a field of the specified type.

In the implementation of this call-back method, you should consider invoking serialize(Object, Type) method to create JsonElements for any non-trivial field of the src object. However, you should never invoke it on the src object itself since that will cause an infinite loop (Gson will call your call-back method again).

Parameters
src the object that needs to be converted to Json.
typeOfSrc the actual type (fully genericized version) of the source object.
Returns
  • a JsonElement corresponding to the specified object.