Java tutorial
/* * 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; import java.lang.reflect.Field; import java.util.Locale; /** * An enumeration that defines a few standard naming conventions for JSON field names. * This enumeration should be used in conjunction with {@link com.google.gson.GsonBuilder} * to configure a {@link com.google.gson.Gson} instance to properly translate Java field * names into the desired JSON field names. * * @author Inderjeet Singh * @author Joel Leitch */ public enum FieldNamingPolicy implements FieldNamingStrategy { /** * Using this naming policy with Gson will ensure that the field name is * unchanged. */ IDENTITY() { @Override public String translateName(Field f) { return f.getName(); } }, /** * Using this naming policy with Gson will ensure that the first "letter" of the Java * field name is capitalized when serialized to its JSON form. * * <p>Here's a few examples of the form "Java Field Name" ---> "JSON Field Name":</p> * <ul> * <li>someFieldName ---> SomeFieldName</li> * <li>_someFieldName ---> _SomeFieldName</li> * </ul> */ UPPER_CAMEL_CASE() { @Override public String translateName(Field f) { return upperCaseFirstLetter(f.getName()); } }, /** * Using this naming policy with Gson will ensure that the first "letter" of the Java * field name is capitalized when serialized to its JSON form and the words will be * separated by a space. * * <p>Here's a few examples of the form "Java Field Name" ---> "JSON Field Name":</p> * <ul> * <li>someFieldName ---> Some Field Name</li> * <li>_someFieldName ---> _Some Field Name</li> * </ul> * * @since 1.4 */ UPPER_CAMEL_CASE_WITH_SPACES() { @Override public String translateName(Field f) { return upperCaseFirstLetter(separateCamelCase(f.getName(), " ")); } }, /** * Using this naming policy with Gson will modify the Java Field name from its camel cased * form to a lower case field name where each word is separated by an underscore (_). * * <p>Here's a few examples of the form "Java Field Name" ---> "JSON Field Name":</p> * <ul> * <li>someFieldName ---> some_field_name</li> * <li>_someFieldName ---> _some_field_name</li> * <li>aStringField ---> a_string_field</li> * <li>aURL ---> a_u_r_l</li> * </ul> */ LOWER_CASE_WITH_UNDERSCORES() { @Override public String translateName(Field f) { return separateCamelCase(f.getName(), "_").toLowerCase(Locale.ENGLISH); } }, /** * Using this naming policy with Gson will modify the Java Field name from its camel cased * form to a lower case field name where each word is separated by a dash (-). * * <p>Here's a few examples of the form "Java Field Name" ---> "JSON Field Name":</p> * <ul> * <li>someFieldName ---> some-field-name</li> * <li>_someFieldName ---> _some-field-name</li> * <li>aStringField ---> a-string-field</li> * <li>aURL ---> a-u-r-l</li> * </ul> * Using dashes in JavaScript is not recommended since dash is also used for a minus sign in * expressions. This requires that a field named with dashes is always accessed as a quoted * property like {@code myobject['my-field']}. Accessing it as an object field * {@code myobject.my-field} will result in an unintended javascript expression. * @since 1.4 */ LOWER_CASE_WITH_DASHES() { @Override public String translateName(Field f) { return separateCamelCase(f.getName(), "-").toLowerCase(Locale.ENGLISH); } }, /** * Using this naming policy with Gson will modify the Java Field name from its camel cased * form to a lower case field name where each word is separated by a dot (.). * * <p>Here's a few examples of the form "Java Field Name" ---> "JSON Field Name":</p> * <ul> * <li>someFieldName ---> some.field.name</li> * <li>_someFieldName ---> _some.field.name</li> * <li>aStringField ---> a.string.field</li> * <li>aURL ---> a.u.r.l</li> * </ul> * Using dots in JavaScript is not recommended since dot is also used for a member sign in * expressions. This requires that a field named with dots is always accessed as a quoted * property like {@code myobject['my.field']}. Accessing it as an object field * {@code myobject.my.field} will result in an unintended javascript expression. * @since 2.8 */ LOWER_CASE_WITH_DOTS() { @Override public String translateName(Field f) { return separateCamelCase(f.getName(), ".").toLowerCase(Locale.ENGLISH); } }; /** * Converts the field name that uses camel-case define word separation into * separate words that are separated by the provided {@code separatorString}. */ static String separateCamelCase(String name, String separator) { StringBuilder translation = new StringBuilder(); for (int i = 0, length = name.length(); i < length; i++) { char character = name.charAt(i); if (Character.isUpperCase(character) && translation.length() != 0) { translation.append(separator); } translation.append(character); } return translation.toString(); } /** * Ensures the JSON field names begins with an upper case letter. */ static String upperCaseFirstLetter(String name) { int firstLetterIndex = 0; int limit = name.length() - 1; for (; !Character.isLetter(name.charAt(firstLetterIndex)) && firstLetterIndex < limit; ++firstLetterIndex) ; char firstLetter = name.charAt(firstLetterIndex); if (Character.isUpperCase(firstLetter)) { //The letter is already uppercased, return the original return name; } char uppercased = Character.toUpperCase(firstLetter); if (firstLetterIndex == 0) { //First character in the string is the first letter, saves 1 substring return uppercased + name.substring(1); } return name.substring(0, firstLetterIndex) + uppercased + name.substring(firstLetterIndex + 1); } }