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collect-library/src/main/java/com/google/gson/FieldNamingPolicy.java

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+/*
+ * 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;
+
+/**
+ * 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();
+    }
+  },
+
+  /**
+   * 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();
+    }
+  };
+
+  /**
+   * Converts the field name that uses camel-case define word separation into
+   * separate words that are separated by the provided {@code separatorString}.
+   */
+  private static String separateCamelCase(String name, String separator) {
+    StringBuilder translation = new StringBuilder();
+    for (int i = 0; i < name.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.
+   */
+  private static String upperCaseFirstLetter(String name) {
+    StringBuilder fieldNameBuilder = new StringBuilder();
+    int index = 0;
+    char firstCharacter = name.charAt(index);
+
+    while (index < name.length() - 1) {
+      if (Character.isLetter(firstCharacter)) {
+        break;
+      }
+
+      fieldNameBuilder.append(firstCharacter);
+      firstCharacter = name.charAt(++index);
+    }
+
+    if (index == name.length()) {
+      return fieldNameBuilder.toString();
+    }
+
+    if (!Character.isUpperCase(firstCharacter)) {
+      String modifiedTarget = modifyString(Character.toUpperCase(firstCharacter), name, ++index);
+      return fieldNameBuilder.append(modifiedTarget).toString();
+    } else {
+      return name;
+    }
+  }
+
+  private static String modifyString(char firstCharacter, String srcString, int indexOfSubstring) {
+    return (indexOfSubstring < srcString.length())
+        ? firstCharacter + srcString.substring(indexOfSubstring)
+        : String.valueOf(firstCharacter);
+  }
+}