| /* |
| * Copyright (C) 2014 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.annotations; |
| |
| import com.google.gson.JsonDeserializer; |
| import com.google.gson.JsonSerializer; |
| import com.google.gson.TypeAdapter; |
| import com.google.gson.TypeAdapterFactory; |
| import java.lang.annotation.ElementType; |
| import java.lang.annotation.Retention; |
| import java.lang.annotation.RetentionPolicy; |
| import java.lang.annotation.Target; |
| |
| /** |
| * An annotation that indicates the Gson {@link TypeAdapter} to use with a class |
| * or field. |
| * |
| * <p>Here is an example of how this annotation is used:</p> |
| * <pre> |
| * @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]); |
| * } |
| * } |
| * </pre> |
| * |
| * Since User class specified UserJsonAdapter.class in @JsonAdapter annotation, it |
| * will automatically be invoked to serialize/deserialize User instances. <br> |
| * |
| * <p> Here is an example of how to apply this annotation to a field. |
| * <pre> |
| * private static final class Gadget { |
| * @JsonAdapter(UserJsonAdapter2.class) |
| * final User user; |
| * Gadget(User user) { |
| * this.user = user; |
| * } |
| * } |
| * </pre> |
| * |
| * It's possible to specify different type adapters on a field, that |
| * field's type, and in the {@link com.google.gson.GsonBuilder}. Field |
| * annotations take precedence over {@code GsonBuilder}-registered type |
| * adapters, which in turn take precedence over annotated types. |
| * |
| * <p>The class referenced by this annotation must be either a {@link |
| * TypeAdapter} or a {@link TypeAdapterFactory}, or must implement one |
| * or both of {@link JsonDeserializer} or {@link JsonSerializer}. |
| * Using {@link TypeAdapterFactory} makes it possible to delegate |
| * to the enclosing {@code Gson} instance. |
| * |
| * @since 2.3 |
| * |
| * @author Inderjeet Singh |
| * @author Joel Leitch |
| * @author Jesse Wilson |
| */ |
| // Note that the above example is taken from AdaptAnnotationTest. |
| @Retention(RetentionPolicy.RUNTIME) |
| @Target({ElementType.TYPE, ElementType.FIELD}) |
| public @interface JsonAdapter { |
| |
| /** Either a {@link TypeAdapter} or {@link TypeAdapterFactory}, or one or both of {@link JsonDeserializer} or {@link JsonSerializer}. */ |
| Class<?> value(); |
| |
| /** false, to be able to handle {@code null} values within the adapter, default value is true. */ |
| boolean nullSafe() default true; |
| |
| } |