jsonobject.java

JSON使用源码,对于AJAX与服务器数据交换,采用JSON作为数据传输格式是个不错的选择

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.util.Collection;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.io.IOException;
import java.io.Writer;

/**
 * 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 sa An array of strings.
     * @exception JSONException If a value is a non-finite number.
     */
    public JSONObject(JSONObject jo, String[] sa) throws JSONException {
        this();
        for (int i = 0; i < sa.length; i += 1) {
            putOpt(sa[i], jo.opt(sa[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;
                }
                x.back();
                break;
            case '}':
                return;
            default:
                throw x.syntaxError("Expected a ',' or '}'");
            }
        }
    }


    /**
     * Construct a JSONObject from a Map.
     * @param map A map object that can be used to initialize the contents of
     *  the JSONObject.
     */
    public JSONObject(Map map) {
        this.myHashMap = (map == null) ?
        	new HashMap() :
        	new HashMap(map);
    }

    
    /**
     * Construct a JSONObject from an Object, using reflection to find the
     * public members. The resulting JSONObject's keys will be the strings
     * from the names array, and the values will be the field values associated
     * with those keys in the object. If a key is not found or not visible,
     * then it will not be copied into the new JSONObject.
     * @param object An object that has fields that should be used to make a
     * JSONObject.
     * @param names An array of strings, the names of the fields to be used
     * from the object.
     */
    public JSONObject(Object object, String names[]) {
    	this();
    	Class c = object.getClass();
    	for (int i = 0; i < names.length; i += 1) {
    		try {
    			String name = names[i];
    			Field field = c.getField(name);
    			Object value = field.get(object);
	    		this.put(name, value);
    		} catch (Exception e) {
    			/* forget about it */
    		}
    	}
    }


    /**
     * Construct a JSONObject from a string.
     * This is the most commonly used JSONObject constructor.
     * @param string    A string beginning
     *  with <code>{</code>&nbsp;<small>(left brace)</small> and ending
     *  with <code>}</code>&nbsp;<small>(right brace)</small>.
     * @exception JSONException If there is a syntax error in the source string.
     */
    public JSONObject(String string) throws JSONException {
        this(new JSONTokener(string));
    }


    /**
     * Accumulate values under a key. It is similar to the put method except
     * that if there is already an object stored under the key then a
     * JSONArray is stored under the key to hold all of the accumulated values.
     * If there is already a JSONArray, then the new value is appended to it.
     * In contrast, the put method replaces the previous value.
     * @param key   A key string.
     * @param value An object to be accumulated under the key.
     * @return this.
     * @throws JSONException If the value is an invalid number
     *  or if the key is null.
     */
    public JSONObject accumulate(String key, Object value)
            throws JSONException {
        testValidity(value);
        Object o = opt(key);
        if (o == null) {
            put(key, value instanceof JSONArray ? 
            		new JSONArray().put(value) : 
                    value);
        } else if (o instanceof JSONArray) {
            ((JSONArray)o).put(value);
        } else {
            put(key, new JSONArray().put(o).put(value));
        }
        return this;
    }


    /**
     * Append values to the array under a key. If the key does not exist in the
     * JSONObject, then the key is put in the JSONObject with its value being a
     * JSONArray containing the value parameter. If the key was already
     * associated with a JSONArray, then the value parameter is appended to it.
     * @param key   A key string.
     * @param value An object to be accumulated under the key.
     * @return this.
     * @throws JSONException If the key is null or if the current value 
     * 	associated with the key is not a JSONArray.
     */
    public JSONObject append(String key, Object value)
            throws JSONException {
        testValidity(value);
        Object o = opt(key);
        if (o == null) {
            put(key, new JSONArray().put(value));
        } else if (o instanceof JSONArray) {
            put(key, ((JSONArray)o).put(value));
        } else {
            throw new JSONException("JSONObject[" + key + 
            		"] is not a JSONArray.");
        }
        return this;
    }


    /**
     * Produce a string from a double. The string "null" will be returned if
     * the number is not finite.
     * @param  d A double.
     * @return A String.
     */
    static public String doubleToString(double d) {
        if (Double.isInfinite(d) || Double.isNaN(d)) {
        	return "null";
        }

// Shave off trailing zeros and decimal point, if possible.

        String s = Double.toString(d);
        if (s.indexOf('.') > 0 && s.indexOf('e') < 0 && s.indexOf('E') < 0) {
            while (s.endsWith("0")) {
                s = s.substring(0, s.length() - 1);
            }
            if (s.endsWith(".")) {
                s = s.substring(0, s.length() - 1);
            }
        }
        return s;
    }


    /**
     * Get the value object associated with a key.
     *
     * @param key   A key string.
     * @return      The object associated with the key.
     * @throws   JSONException if the key is not found.
     */
    public Object get(String key) throws JSONException {
        Object o = opt(key);
        if (o == null) {
            throw new JSONException("JSONObject[" + quote(key) +
                    "] not found.");
        }
        return o;
    }


    /**
     * Get the boolean value associated with a key.
     *
     * @param key   A key string.
     * @return      The truth.
     * @throws   JSONException
     *  if the value is not a Boolean or the String "true" or "false".
     */
    public boolean getBoolean(String key) throws JSONException {
        Object o = get(key);
        if (o.equals(Boolean.FALSE) ||
                (o instanceof String &&
                ((String)o).equalsIgnoreCase("false"))) {
            return false;
        } else if (o.equals(Boolean.TRUE) ||
                (o instanceof String &&
                ((String)o).equalsIgnoreCase("true"))) {
            return true;
        }
        throw new JSONException("JSONObject[" + quote(key) +
                "] is not a Boolean.");
    }


    /**
     * Get the double value associated with a key.
     * @param key   A key string.
     * @return      The numeric value.
     * @throws JSONException if the key is not found or
     *  if the value is not a Number object and cannot be converted to a number.
     */
    public double getDouble(String key) throws JSONException {
        Object o = get(key);
        try {
            return o instanceof Number ?
                ((Number)o).doubleValue() : 
                Double.valueOf((String)o).doubleValue();
        } catch (Exception e) {
            throw new JSONException("JSONObject[" + quote(key) +
                "] is not a number.");
        }
    }