| /* |
| * Copyright 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.gwt.json.client; |
| |
| import com.google.gwt.core.client.JavaScriptObject; |
| |
| /** |
| * Represents the JSON <code>null</code> value. |
| */ |
| public class JSONNull extends JSONValue { |
| |
| private static final JSONNull instance = new JSONNull(); |
| |
| /** |
| * Returns the singleton null-valued JSON object. |
| */ |
| public static JSONNull getInstance() { |
| return instance; |
| } |
| |
| /** |
| * Called from {@link #getUnwrapper()}. |
| */ |
| private static JavaScriptObject unwrap() { |
| return null; |
| } |
| |
| /** |
| * There should only be one null value. |
| */ |
| private JSONNull() { |
| } |
| |
| /** |
| * Returns <code>this</code>, as this is a JSONNull. |
| */ |
| @Override |
| public JSONNull isNull() { |
| // Workaround for https://code.google.com/p/google-web-toolkit/issues/detail?id=8139 |
| if (this != instance) { |
| return null; |
| } |
| return this; |
| } |
| |
| /** |
| * Returns "null" to allow for formatting <code>null</code> values. |
| */ |
| @Override |
| public String toString() { |
| return "null"; |
| } |
| |
| @Override |
| native JavaScriptObject getUnwrapper() /*-{ |
| return @com.google.gwt.json.client.JSONNull::unwrap(); |
| }-*/; |
| |
| } |