@Retention(value=RUNTIME)
@Target(value={TYPE,FIELD})
public @interface JsonAdapter
TypeAdapter
to use with a class
or field.
Here is an example of how this annotation is used:
@JsonAdapter(UserJsonAdapter.class) public class User { public final String firstName, lastName; private User(String firstName, String lastName) { this.firstName = firstName; this.lastName = lastName; } } public class UserJsonAdapter extends TypeAdapter<User> { @Override public void write(JsonWriter out, User user) throws IOException { // implement write: combine firstName and lastName into name out.beginObject(); out.name("name"); out.value(user.firstName + " " + user.lastName); out.endObject(); // implement the write method } @Override public User read(JsonReader in) throws IOException { // implement read: split name into firstName and lastName in.beginObject(); in.nextName(); String[] nameParts = in.nextString().split(" "); in.endObject(); return new User(nameParts[0], nameParts[1]); } }Since User class specified UserJsonAdapter.class in @JsonAdapter annotation, it will automatically be invoked to serialize/deserialize User instances.
Here is an example of how to apply this annotation to a field.
private static final class Gadget { @JsonAdapter(UserJsonAdapter2.class) final User user; Gadget(User user) { this.user = user; } }It's possible to specify different type adapters on a field, that field's type, and in the
GsonBuilder
. Field
annotations take precedence over GsonBuilder
-registered type
adapters, which in turn take precedence over annotated types.
The class referenced by this annotation must be either a TypeAdapter
or a TypeAdapterFactory
, or must implement one
or both of JsonDeserializer
or JsonSerializer
.
Using TypeAdapterFactory
makes it possible to delegate
to the enclosing Gson
instance.
Modifier and Type | Required Element and Description |
---|---|
java.lang.Class<?> |
value
|
Modifier and Type | Optional Element and Description |
---|---|
boolean |
nullSafe
false, to be able to handle
null values within the adapter, default value is true. |
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