src/com/google/gson/FieldNamingPolicy.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;
  18
  19 import java.lang.reflect.Field;
  20
  21 /**
  22  * An enumeration that defines a few standard naming conventions for JSON field names.
  23  * This enumeration should be used in conjunction with {@link com.google.gson.GsonBuilder}
  24  * to configure a {@link com.google.gson.Gson} instance to properly translate Java field
  25  * names into the desired JSON field names.
  26  *
  27  * @author Inderjeet Singh
  28  * @author Joel Leitch
  29  */
  30 public enum FieldNamingPolicy implements FieldNamingStrategy {
  31
  32   /**
  33    * Using this naming policy with Gson will ensure that the field name is
  34    * unchanged.
  35    */
  36   IDENTITY() {
  37     public String translateName(Field f) {
  38       return f.getName();
  39     }
  40   },
  41
  42   /**
  43    * Using this naming policy with Gson will ensure that the first "letter" of the Java
  44    * field name is capitalized when serialized to its JSON form.
  45    *
  46    * <p>Here's a few examples of the form "Java Field Name" ---> "JSON Field Name":</p>
  47    * <ul>
  48    *   <li>someFieldName ---> SomeFieldName</li>
  49    *   <li>_someFieldName ---> _SomeFieldName</li>
  50    * </ul>
  51    */
  52   UPPER_CAMEL_CASE() {
  53     public String translateName(Field f) {
  54       return upperCaseFirstLetter(f.getName());
  55     }
  56   },
  57
  58   /**
  59    * Using this naming policy with Gson will ensure that the first "letter" of the Java
  60    * field name is capitalized when serialized to its JSON form and the words will be
  61    * separated by a space.
  62    *
  63    * <p>Here's a few examples of the form "Java Field Name" ---> "JSON Field Name":</p>
  64    * <ul>
  65    *   <li>someFieldName ---> Some Field Name</li>
  66    *   <li>_someFieldName ---> _Some Field Name</li>
  67    * </ul>
  68    *
  69    * @since 1.4
  70    */
  71   UPPER_CAMEL_CASE_WITH_SPACES() {
  72     public String translateName(Field f) {
  73       return upperCaseFirstLetter(separateCamelCase(f.getName(), " "));
  74     }
  75   },
  76
  77   /**
  78    * Using this naming policy with Gson will modify the Java Field name from its camel cased
  79    * form to a lower case field name where each word is separated by an underscore (_).
  80    *
  81    * <p>Here's a few examples of the form "Java Field Name" ---> "JSON Field Name":</p>
  82    * <ul>
  83    *   <li>someFieldName ---> some_field_name</li>
  84    *   <li>_someFieldName ---> _some_field_name</li>
  85    *   <li>aStringField ---> a_string_field</li>
  86    *   <li>aURL ---> a_u_r_l</li>
  87    * </ul>
  88    */
  89   LOWER_CASE_WITH_UNDERSCORES() {
  90     public String translateName(Field f) {
  91       return separateCamelCase(f.getName(), "_").toLowerCase();
  92     }
  93   },
  94
  95   /**
  96    * Using this naming policy with Gson will modify the Java Field name from its camel cased
  97    * form to a lower case field name where each word is separated by a dash (-).
  98    *
  99    * <p>Here's a few examples of the form "Java Field Name" ---> "JSON Field Name":</p>
 100    * <ul>
 101    *   <li>someFieldName ---> some-field-name</li>
 102    *   <li>_someFieldName ---> _some-field-name</li>
 103    *   <li>aStringField ---> a-string-field</li>
 104    *   <li>aURL ---> a-u-r-l</li>
 105    * </ul>
 106    * Using dashes in JavaScript is not recommended since dash is also used for a minus sign in
 107    * expressions. This requires that a field named with dashes is always accessed as a quoted
 108    * property like {@code myobject['my-field']}. Accessing it as an object field
 109    * {@code myobject.my-field} will result in an unintended javascript expression.
 110    * @since 1.4
 111    */
 112   LOWER_CASE_WITH_DASHES() {
 113     public String translateName(Field f) {
 114       return separateCamelCase(f.getName(), "-").toLowerCase();
 115     }
 116   };
 117
 118   /**
 119    * Converts the field name that uses camel-case define word separation into
 120    * separate words that are separated by the provided {@code separatorString}.
 121    */
 122   private static String separateCamelCase(String name, String separator) {
 123     StringBuilder translation = new StringBuilder();
 124     for (int i = 0; i < name.length(); i++) {
 125       char character = name.charAt(i);
 126       if (Character.isUpperCase(character) && translation.length() != 0) {
 127         translation.append(separator);
 128       }
 129       translation.append(character);
 130     }
 131     return translation.toString();
 132   }
 133
 134   /**
 135    * Ensures the JSON field names begins with an upper case letter.
 136    */
 137   private static String upperCaseFirstLetter(String name) {
 138     StringBuilder fieldNameBuilder = new StringBuilder();
 139     int index = 0;
 140     char firstCharacter = name.charAt(index);
 141
 142     while (index < name.length() - 1) {
 143       if (Character.isLetter(firstCharacter)) {
 144         break;
 145       }
 146
 147       fieldNameBuilder.append(firstCharacter);
 148       firstCharacter = name.charAt(++index);
 149     }
 150
 151     if (index == name.length()) {
 152       return fieldNameBuilder.toString();
 153     }
 154
 155     if (!Character.isUpperCase(firstCharacter)) {
 156       String modifiedTarget = modifyString(Character.toUpperCase(firstCharacter), name, ++index);
 157       return fieldNameBuilder.append(modifiedTarget).toString();
 158     } else {
 159       return name;
 160     }
 161   }
 162
 163   private static String modifyString(char firstCharacter, String srcString, int indexOfSubstring) {
 164     return (indexOfSubstring < srcString.length())
 165         ? firstCharacter + srcString.substring(indexOfSubstring)
 166         : String.valueOf(firstCharacter);
 167   }
 168 }