gson/com/google/gson/annotations/Until.java

   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 the version number until a member or a type should be present.
  26  * Basically, if Gson is created with a version number that exceeds the value stored in the
  27  * {@code Until} annotation then the field will be ignored from the JSON output.  This annotation
  28  * is useful to manage versioning of your JSON classes for a web-service.
  29  *
  30  * <p>
  31  * This annotation has no effect unless you build {@link com.google.gson.Gson} with a
  32  * {@link com.google.gson.GsonBuilder} and invoke
  33  * {@link com.google.gson.GsonBuilder#setVersion(double)} method.
  34  *
  35  * <p>Here is an example of how this annotation is meant to be used:</p>
  36  * <pre>
  37  * public class User {
  38  *   private String firstName;
  39  *   private String lastName;
  40  *   &#64Until(1.1) private String emailAddress;
  41  *   &#64Until(1.1) private String password;
  42  * }
  43  * </pre>
  44  *
  45  * <p>If you created Gson with {@code new Gson()}, the {@code toJson()} and {@code fromJson()}
  46  * methods will use all the fields for serialization and deserialization. However, if you created
  47  * Gson with {@code Gson gson = new GsonBuilder().setVersion(1.2).create()} then the
  48  * {@code toJson()} and {@code fromJson()} methods of Gson will exclude the {@code emailAddress}
  49  * and {@code password} fields from the example above, because the version number passed to the
  50  * GsonBuilder, {@code 1.2}, exceeds the version number set on the {@code Until} annotation,
  51  * {@code 1.1}, for those fields.
  52  *
  53  * @author Inderjeet Singh
  54  * @author Joel Leitch
  55  * @since 1.3
  56  */
  57 @Retention(RetentionPolicy.RUNTIME)
  58 @Target({ElementType.FIELD, ElementType.TYPE})
  59 public @interface Until {
  60
  61   /**
  62    * the value indicating a version number until this member
  63    * or type should be ignored.
  64    */
  65   double value();
  66 }