github.com/keysonZZZ/kmg@v0.0.0-20151121023212-05317bfd7d39/kmgRpc/kmgRpcJava/java/src/com/google/gson/annotations/Expose.java (about)

     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   *   &#64Expose private String firstName;
    37   *   &#64Expose(serialize = false) private String lastName;
    38   *   &#64Expose (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  }