Overview | Package | Class | Use | Tree | Deprecated | Index | Help
PREV CLASS NEXT CLASS | FRAMES NO FRAMES
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD

## com.google.gson
Interface JsonDeserializer<T>

Type Parameters:
  `T` - type for which the deserializer is being registered. It is possible that a deserializer may be asked to deserialize a specific generic type of the T.

    public interface JsonDeserializer<T>

Interface representing a custom deserializer for Json. You should write a custom deserializer, if you are not happy with the default deserialization done by Gson. You will also need to register this deserializer through `GsonBuilder.registerTypeAdapter(Type, Object)`.

Let us look at example where defining a deserializer 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 deserialization of `Id(com.foo.MyObject.class, 20L)` will require the Json string to be `{"clazz":com.foo.MyObject,"value":20}`. Suppose, you already know the type of the field that the `Id` will be deserialized into, and hence just want to deserialize it from a Json string `20`. You can achieve that by writing a custom deserializer:

     class IdDeserializer implements JsonDeserializer<Id>() {
       public Id deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
           throws JsonParseException {
         return new Id((Class)typeOfT, id.getValue());
       }

You will also need to register `IdDeserializer` with Gson as follows:

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

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

Author:
  Inderjeet Singh, Joel Leitch

Method Summary
`T` | `deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)` Gson invokes this call-back method during deserialization when it encounters a field of the specified type.

Method Detail

### deserialize

    T deserialize(JsonElement json,
                  Type typeOfT,
                  JsonDeserializationContext context)
                  throws JsonParseException

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

  In the implementation of this call-back method, you should consider invoking `JsonDeserializationContext.deserialize(JsonElement, Type)` method to create objects for any non-trivial field of the returned object. However, you should never invoke it on the the same type passing `json` since that will cause an infinite loop (Gson will call your call-back method again).

  Parameters:
    `json` - The Json data being deserialized
    `typeOfT` - The type of the Object to deserialize to
  Returns:
    a deserialized object of the specified type typeOfT which is a subclass of `T`
  Throws:
    `JsonParseException` - if json is not in the expected format of `typeofT`

Overview | Package | Class | Use | Tree | Deprecated | Index | Help
PREV CLASS NEXT CLASS | FRAMES NO FRAMES
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD

Copyright © 2008–2014 Google, Inc.. All rights reserved.