| 1 | /* |
| 2 | * Copyright (C) 2008 Google Inc. |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package com.google.gson.annotations; |
| 18 | |
| 19 | import java.lang.annotation.ElementType; |
| 20 | import java.lang.annotation.Retention; |
| 21 | import java.lang.annotation.RetentionPolicy; |
| 22 | import java.lang.annotation.Target; |
| 23 | |
| 24 | /** |
| 25 | * An annotation that indicates this member should be exposed for JSON |
| 26 | * serialization or deserialization. |
| 27 | * |
| 28 | * <p>This annotation has no effect unless you build {@link com.google.gson.Gson} |
| 29 | * with a {@link com.google.gson.GsonBuilder} and invoke |
| 30 | * {@link com.google.gson.GsonBuilder#excludeFieldsWithoutExposeAnnotation()} |
| 31 | * method.</p> |
| 32 | * |
| 33 | * <p>Here is an example of how this annotation is meant to be used: |
| 34 | * <p><pre> |
| 35 | * public class User { |
| 36 | * @Expose private String firstName; |
| 37 | * @Expose(serialize = false) private String lastName; |
| 38 | * @Expose (serialize = false, deserialize = false) private String emailAddress; |
| 39 | * private String password; |
| 40 | * } |
| 41 | * </pre></p> |
| 42 | * If you created Gson with {@code new Gson()}, the {@code toJson()} and {@code fromJson()} |
| 43 | * methods will use the {@code password} field along-with {@code firstName}, {@code lastName}, |
| 44 | * and {@code emailAddress} for serialization and deserialization. However, if you created Gson |
| 45 | * with {@code Gson gson = new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create()} |
| 46 | * then the {@code toJson()} and {@code fromJson()} methods of Gson will exclude the |
| 47 | * {@code password} field. This is because the {@code password} field is not marked with the |
| 48 | * {@code @Expose} annotation. Gson will also exclude {@code lastName} and {@code emailAddress} |
| 49 | * from serialization since {@code serialize} is set to {@code false}. Similarly, Gson will |
| 50 | * exclude {@code emailAddress} from deserialization since {@code deserialize} is set to false. |
| 51 | * |
| 52 | * <p>Note that another way to achieve the same effect would have been to just mark the |
| 53 | * {@code password} field as {@code transient}, and Gson would have excluded it even with default |
| 54 | * settings. The {@code @Expose} annotation is useful in a style of programming where you want to |
| 55 | * explicitly specify all fields that should get considered for serialization or deserialization. |
| 56 | * |
| 57 | * @author Inderjeet Singh |
| 58 | * @author Joel Leitch |
| 59 | */ |
| 60 | @Retention(RetentionPolicy.RUNTIME) |
| 61 | @Target(ElementType.FIELD) |
| 62 | public @interface Expose { |
| 63 | |
| 64 | /** |
| 65 | * If {@code true}, the field marked with this annotation is written out in the JSON while |
| 66 | * serializing. If {@code false}, the field marked with this annotation is skipped from the |
| 67 | * serialized output. Defaults to {@code true}. |
| 68 | * @since 1.4 |
| 69 | */ |
| 70 | public boolean serialize() default true; |
| 71 | |
| 72 | /** |
| 73 | * If {@code true}, the field marked with this annotation is deserialized from the JSON. |
| 74 | * If {@code false}, the field marked with this annotation is skipped during deserialization. |
| 75 | * Defaults to {@code true}. |
| 76 | * @since 1.4 |
| 77 | */ |
| 78 | public boolean deserialize() default true; |
| 79 | } |