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Explore the source code of the class Expose.java

/*
 * 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.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 */ @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; }