com.google.gson.annotations.Expose Maven / Gradle / Ivy
/*
* Copyright (C) 2008 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 java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* An annotation that indicates this member should be exposed for JSON
* serialization or deserialization.
*
* This annotation has no effect unless you build {@link com.google.gson.Gson}
* with a {@link com.google.gson.GsonBuilder} and invoke
* {@link com.google.gson.GsonBuilder#excludeFieldsWithoutExposeAnnotation()}
* method.
*
* Here is an example of how this annotation is meant to be used:
*
* public class User {
* @Expose private String firstName;
* @Expose(serialize = false) private String lastName;
* @Expose (serialize = false, deserialize = false) private String emailAddress;
* private String password;
* }
*
* If you created Gson with {@code new Gson()}, the {@code toJson()} and {@code fromJson()}
* methods will use the {@code password} field along-with {@code firstName}, {@code lastName},
* and {@code emailAddress} for serialization and deserialization. However, if you created Gson
* with {@code Gson gson = new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create()}
* then the {@code toJson()} and {@code fromJson()} methods of Gson will exclude the
* {@code password} field. This is because the {@code password} field is not marked with the
* {@code @Expose} annotation. Gson will also exclude {@code lastName} and {@code emailAddress}
* from serialization since {@code serialize} is set to {@code false}. Similarly, Gson will
* exclude {@code emailAddress} from deserialization since {@code deserialize} is set to false.
*
* Note that another way to achieve the same effect would have been to just mark the
* {@code password} field as {@code transient}, and Gson would have excluded it even with default
* settings. The {@code @Expose} annotation is useful in a style of programming where you want to
* explicitly specify all fields that should get considered for serialization or deserialization.
*
* @author Inderjeet Singh
* @author Joel Leitch
*/
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface Expose {
/**
* If {@code true}, the field marked with this annotation is written out in the JSON while
* serializing. If {@code false}, the field marked with this annotation is skipped from the
* serialized output. Defaults to {@code true}.
* @since 1.4
*/
public boolean serialize() default true;
/**
* If {@code true}, the field marked with this annotation is deserialized from the JSON.
* If {@code false}, the field marked with this annotation is skipped during deserialization.
* Defaults to {@code true}.
* @since 1.4
*/
public boolean deserialize() default true;
}