经典Structs教程

package org.json; /* Copyright (c) 2002 JSON.org Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. The Software shall be used for Good, not Evil. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */ import java.io.IOException; import java.io.Writer; import java.util.Collection; import java.lang.reflect.Field; import java.lang.reflect.Method; import java.util.HashMap; import java.util.Iterator; import java.util.Map; /** * A JSONObject is an unordered collection of name/value pairs. Its * external form is a string wrapped in curly braces with colons between the * names and values, and commas between the values and names. The internal form * is an object having <code>get</code> and <code>opt</code> methods for * accessing the values by name, and <code>put</code> methods for adding or * replacing values by name. The values can be any of these types: * <code>Boolean</code>, <code>JSONArray</code>, <code>JSONObject</code>, * <code>Number</code>, <code>String</code>, or the <code>JSONObject.NULL</code> * object. A JSONObject constructor can be used to convert an external form * JSON text into an internal form whose values can be retrieved with the * <code>get</code> and <code>opt</code> methods, or to convert values into a * JSON text using the <code>put</code> and <code>toString</code> methods. * A <code>get</code> method returns a value if one can be found, and throws an * exception if one cannot be found. An <code>opt</code> method returns a * default value instead of throwing an exception, and so is useful for * obtaining optional values. * <p> * The generic <code>get()</code> and <code>opt()</code> methods return an * object, which you can cast or query for type. There are also typed * <code>get</code> and <code>opt</code> methods that do type checking and type * coersion for you. * <p> * The <code>put</code> methods adds values to an object. For example, <pre> * myString = new JSONObject().put("JSON", "Hello, World!").toString();</pre> * produces the string <code>{"JSON": "Hello, World"}</code>. * <p> * The texts produced by the <code>toString</code> methods strictly conform to * the JSON sysntax rules. * The constructors are more forgiving in the texts they will accept: * <ul> * <li>An extra <code>,</code>&nbsp;<small>(comma)</small> may appear just * before the closing brace.</li> * <li>Strings may be quoted with <code>'</code>&nbsp;<small>(single * quote)</small>.</li> * <li>Strings do not need to be quoted at all if they do not begin with a quote * or single quote, and if they do not contain leading or trailing spaces, * and if they do not contain any of these characters: * <code>{ } [ ] / \ : , = ; #</code> and if they do not look like numbers * and if they are not the reserved words <code>true</code>, * <code>false</code>, or <code>null</code>.</li> * <li>Keys can be followed by <code>=</code> or <code>=></code> as well as * by <code>:</code>.</li> * <li>Values can be followed by <code>;</code> <small>(semicolon)</small> as * well as by <code>,</code> <small>(comma)</small>.</li> * <li>Numbers may have the <code>0-</code> <small>(octal)</small> or * <code>0x-</code> <small>(hex)</small> prefix.</li> * <li>Comments written in the slashshlash, slashstar, and hash conventions * will be ignored.</li> * </ul> * @author JSON.org * @version 2 */ public class JSONObject { /** * JSONObject.NULL is equivalent to the value that JavaScript calls null, * whilst Java's null is equivalent to the value that JavaScript calls * undefined. */ private static final class Null { /** * There is only intended to be a single instance of the NULL object, * so the clone method returns itself. * @return NULL. */ protected final Object clone() { return this; } /** * A Null object is equal to the null value and to itself. * @param object An object to test for nullness. * @return true if the object parameter is the JSONObject.NULL object * or null. */ public boolean equals(Object object) { return object == null || object == this; } /** * Get the "null" string value. * @return The string "null". */ public String toString() { return "null"; } } /** * The hash map where the JSONObject's properties are kept. */ private HashMap myHashMap; /** * It is sometimes more convenient and less ambiguous to have a * <code>NULL</code> object than to use Java's <code>null</code> value. * <code>JSONObject.NULL.equals(null)</code> returns <code>true</code>. * <code>JSONObject.NULL.toString()</code> returns <code>"null"</code>. */ public static final Object NULL = new Null(); /** * Construct an empty JSONObject. */ public JSONObject() { this.myHashMap = new HashMap(); } /** * Construct a JSONObject from a subset of another JSONObject. * An array of strings is used to identify the keys that should be copied. * Missing keys are ignored. * @param jo A JSONObject. * @param names An array of strings. * @exception JSONException If a value is a non-finite number. */ public JSONObject(JSONObject jo, String[] names) throws JSONException { this(); for (int i = 0; i < names.length; i += 1) { putOpt(names[i], jo.opt(names[i])); } } /** * Construct a JSONObject from a JSONTokener. * @param x A JSONTokener object containing the source string. * @throws JSONException If there is a syntax error in the source string. */ public JSONObject(JSONTokener x) throws JSONException { this(); char c; String key; if (x.nextClean() != '{') { throw x.syntaxError("A JSONObject text must begin with '{'"); } for (;;) { c = x.nextClean(); switch (c) { case 0: throw x.syntaxError("A JSONObject text must end with '}'"); case '}': return; default: x.back(); key = x.nextValue().toString(); } /* * The key is followed by ':'. We will also tolerate '=' or '=>'. */ c = x.nextClean(); if (c == '=') { if (x.next() != '>') { x.back(); } } else if (c != ':') { throw x.syntaxError("Expected a ':' after a key"); } put(key, x.nextValue()); /* * Pairs are separated by ','. We will also tolerate ';'. */ switch (x.nextClean()) { case ';': case ',': if (x.nextClean() == '}') { return; }