Java tutorial
/* * 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.GWT; import com.google.gwt.core.client.JavaScriptObject; import com.google.gwt.core.client.JsonUtils; import java.util.AbstractSet; import java.util.ArrayList; import java.util.Arrays; import java.util.Collection; import java.util.Iterator; import java.util.List; import java.util.Set; /** * Represents a JSON object. A JSON object consists of a set of properties. */ public class JSONObject extends JSONValue { /** * Called from {@link #getUnwrapper()}. */ private static JavaScriptObject unwrap(JSONObject value) { return value.jsObject; } private final JavaScriptObject jsObject; public JSONObject() { this(JavaScriptObject.createObject()); } /** * Creates a new JSONObject from the supplied JavaScript value. */ public JSONObject(JavaScriptObject jsValue) { jsObject = jsValue; } /** * Tests whether or not this JSONObject contains the specified property. * * @param key the property to search for * @return <code>true</code> if the JSONObject contains the specified property */ public native boolean containsKey(String key) /*-{ return key in this.@com.google.gwt.json.client.JSONObject::jsObject; }-*/; /** * Returns <code>true</code> if <code>other</code> is a {@link JSONObject} * wrapping the same underlying object. */ @Override public boolean equals(Object other) { if (!(other instanceof JSONObject)) { return false; } return jsObject.equals(((JSONObject) other).jsObject); } /** * Gets the JSONValue associated with the specified property. * * @param key the property to access * @return the value of the specified property, or <code>null</code> if the * property does not exist * @throws NullPointerException if key is <code>null</code> */ public JSONValue get(String key) { if (key == null) { throw new NullPointerException(); } return get0(key); } /** * Returns the underlying JavaScript object that this object wraps. */ public JavaScriptObject getJavaScriptObject() { return jsObject; } @Override public int hashCode() { return jsObject.hashCode(); } /** * Returns <code>this</code>, as this is a JSONObject. */ @Override public JSONObject isObject() { return this; } /** * Returns the set of properties defined on this JSONObject. The returned set * is immutable. */ public Set<String> keySet() { final String[] keys = computeKeys(); return new AbstractSet<String>() { @Override public boolean contains(Object o) { return (o instanceof String) && containsKey((String) o); } @Override public Iterator<String> iterator() { return Arrays.asList(keys).iterator(); } @Override public int size() { return keys.length; } }; } /** * Assign the specified property to the specified value in this JSONObject. If * the property already has an associated value, it is overwritten. * * @param key the property to assign * @param jsonValue the value to assign * @return the previous value of the property, or <code>null</code> if the * property did not exist * @throws NullPointerException if key is <code>null</code> */ public JSONValue put(String key, JSONValue jsonValue) { if (key == null) { throw new NullPointerException(); } JSONValue previous = get(key); put0(key, jsonValue); return previous; } /** * Determines the number of properties on this object. */ public int size() { // Must always recheck due to foreign changes. :( return computeSize(); } /** * Converts a JSONObject into a JSON representation that can be used to * communicate with a JSON service. * * @return a JSON string representation of this JSONObject instance */ @Override public String toString() { StringBuffer sb = new StringBuffer(); sb.append("{"); boolean first = true; String[] keys = computeKeys(); for (String key : keys) { if (first) { first = false; } else { sb.append(", "); } sb.append(JsonUtils.escapeValue(key)); sb.append(":"); sb.append(get(key)); } sb.append("}"); return sb.toString(); } @Override native JavaScriptObject getUnwrapper() /*-{ return @com.google.gwt.json.client.JSONObject::unwrap(Lcom/google/gwt/json/client/JSONObject;); }-*/; private native void addAllKeys(Collection<String> s) /*-{ var jsObject = this.@com.google.gwt.json.client.JSONObject::jsObject; for (var key in jsObject) { if (jsObject.hasOwnProperty(key)) { s.@java.util.Collection::add(Ljava/lang/Object;)(key); } } }-*/; private String[] computeKeys() { if (GWT.isScript()) { return computeKeys0(new String[0]); } else { List<String> result = new ArrayList<String>(); addAllKeys(result); return result.toArray(new String[result.size()]); } } private native String[] computeKeys0(String[] result) /*-{ var jsObject = this.@com.google.gwt.json.client.JSONObject::jsObject; var i = 0; for (var key in jsObject) { if (jsObject.hasOwnProperty(key)) { result[i++] = key; } } return result; }-*/; private native int computeSize() /*-{ var jsObject = this.@com.google.gwt.json.client.JSONObject::jsObject; var size = 0; for (var key in jsObject) { if (jsObject.hasOwnProperty(key)) { ++size; } } return size; }-*/; private native JSONValue get0(String key) /*-{ var jsObject = this.@com.google.gwt.json.client.JSONObject::jsObject; var v; // In Firefox, jsObject.hasOwnProperty(key) requires a primitive string key = String(key); if (jsObject.hasOwnProperty(key)) { v = jsObject[key]; } var func = @com.google.gwt.json.client.JSONParser::typeMap[typeof v]; var ret = func ? func(v) : @com.google.gwt.json.client.JSONParser::throwUnknownTypeException(Ljava/lang/String;)(typeof v); return ret; }-*/; private native void put0(String key, JSONValue value) /*-{ if (value) { var func = value.@com.google.gwt.json.client.JSONValue::getUnwrapper()(); this.@com.google.gwt.json.client.JSONObject::jsObject[key] = func(value); } else { delete this.@com.google.gwt.json.client.JSONObject::jsObject[key]; } }-*/; }