jsonobject.java

《AJAX基础》一书的源码

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.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.text.ParseException;


/**
 * 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 get() and opt() methods for accessing the values by name,
 * and put() methods for adding or replacing values by name. The values can be
 * any of these types: Boolean, JSONArray, JSONObject, Number, String, or the
 * JSONObject.NULL object.
 * <p>
 * The constructor can convert an external form string into an internal form
 * Java object. The toString() method creates an external form string.
 * <p>
 * A get() method returns a value if one can be found, and throws an exception
 * if one cannot be found. An opt() method returns a default value instead of
 * throwing an exception, and so is useful for obtaining optional values.
 * <p>
 * The generic get() and opt() methods return an object, which you can cast or
 * query for type. There are also typed get() and opt() methods that do type
 * checking and type coersion for you.
 * <p>
 * The texts produced by the toString() methods are very strict.
 * 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> as well as by <code>,</code></li>
 * <li>Numbers may have the <code>0-</code> <small>(octal)</small> or 
 *     <code>0x-</code> <small>(hex)</small> prefix.</li> 
 * <li>Line comments can begin with <code>#</code></li>
 * </ul>
 * @author JSON.org
 * @version 1
 */
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 {

        /**
         * Make a Null object.
         */
        private 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 NULL
     * object than to use Java's null value.
     * JSONObject.NULL.equals(null) returns true.
     * JSONObject.NULL.toString() returns "null".
     */
    public static final Object NULL = new Null();

    /**
     * Construct an empty JSONObject.
     */
    public JSONObject() {
        myHashMap = new HashMap();
    }


    /**
     * Construct a JSONObject from a JSONTokener.
     * @throws ParseException if there is a syntax error in the source string.
     * @param x A JSONTokener object containing the source string.
     */
    public JSONObject(JSONTokener x) throws ParseException {
        this();
        char c;
        String key;

        if (x.nextClean() != '{') {
            throw x.syntaxError("A JSONObject must begin with '{'");
        }
        while (true) {
            c = x.nextClean();
            switch (c) {
            case 0:
                throw x.syntaxError("A JSONObject must end with '}'");
            case '}':
                return;
            default:
                x.back();
                key = x.nextValue().toString();
            }
            c = x.nextClean();
			if (c == '=') {
				if (x.next() != '>') {
					x.back();
				}
			} else if (c != ':') {
                throw x.syntaxError("Expected a ':' after a key");
            }
            myHashMap.put(key, x.nextValue());
            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 string.
     * @exception ParseException The string must be properly formatted.
     * @param string    A string beginning 
     *  with <code>{</code>&nbsp;<small>(left brace)</small> and ending 
     *  with <code>}</code>&nbsp;<small>(right brace)</small>.
     */
    public JSONObject(String string) throws ParseException {
        this(new JSONTokener(string));
    }


    /**
     * 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) {
        myHashMap = new HashMap(map);
    }


    /**
     * 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.
     * @throws NullPointerException if the key is null
     * @param key   A key string.
     * @param value An object to be accumulated under the key.
     * @return this.
     */
    public JSONObject accumulate(String key, Object value)
            throws NullPointerException {
        JSONArray a;
        Object o = opt(key);
        if (o == null) {
            put(key, value);
        } else if (o instanceof JSONArray) {
            a = (JSONArray)o;
            a.put(value);
        } else {
            a = new JSONArray();
            a.put(o);
            a.put(value);
            put(key, a);
        }
        return this;
    }


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


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


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


    /**
     * Get the HashMap the holds that contents of the JSONObject.
     * @return The getHashMap.
     */
     HashMap getHashMap() {
        return myHashMap;
     }


    /**
     * Get the int value associated with a key.
     * @exception NoSuchElementException if the key is not found
     * @exception NumberFormatException
     *  if the value cannot be converted to a number.
     *
     * @param key   A key string.
     * @return      The integer value.
     */
    public int getInt(String key)
            throws NoSuchElementException, NumberFormatException {
        Object o = get(key);
        if (o instanceof Number) {
            return ((Number)o).intValue();
        }
        return (int)getDouble(key);
    }


    /**
     * Get the JSONArray value associated with a key.
     * @exception NoSuchElementException if the key is not found or
     *  if the value is not a JSONArray.
     *
     * @param key   A key string.
     * @return      A JSONArray which is the value.
     */
    public JSONArray getJSONArray(String key) throws NoSuchElementException {
        Object o = get(key);
        if (o instanceof JSONArray) {
            return (JSONArray)o;
        }
        throw new NoSuchElementException("JSONObject[" +
            quote(key) + "] is not a JSONArray.");
    }


    /**
     * Get the JSONObject value associated with a key.
     * @exception NoSuchElementException if the key is not found or
     *  if the value is not a JSONObject.
     *
     * @param key   A key string.
     * @return      A JSONObject which is the value.
     */
    public JSONObject getJSONObject(String key) throws NoSuchElementException {
        Object o = get(key);
        if (o instanceof JSONObject) {
            return (JSONObject)o;
        }
        throw new NoSuchElementException("JSONObject[" +
            quote(key) + "] is not a JSONObject.");
    }


    /**
     * Get the string associated with a key.
     * @exception NoSuchElementException if the key is not found.
     *
     * @param key   A key string.
     * @return      A string which is the value.
     */
    public String getString(String key) throws NoSuchElementException {
        return get(key).toString();
    }


    /**
     * Determine if the JSONObject contains a specific key.
     * @param key   A key string.
     * @return      true if the key exists in the JSONObject.
     */
    public boolean has(String key) {
        return myHashMap.containsKey(key);
    }


    /**
     * Determine if the value associated with the key is null or if there is
     *  no value.
     * @param key   A key string.
     * @return      true if there is no value associated with the key or if
     *  the value is the JSONObject.NULL object.
     */
    public boolean isNull(String key) {
        return JSONObject.NULL.equals(opt(key));
    }


    /**
     * Get an enumeration of the keys of the JSONObject.
     *
     * @return An iterator of the keys.
     */
    public Iterator keys() {
        return myHashMap.keySet().iterator();
    }


    /**
     * Get the number of keys stored in the JSONObject.
     *
     * @return The number of keys in the JSONObject.
     */
    public int length() {
        return myHashMap.size();
    }


    /**
     * Produce a JSONArray containing the names of the elements of this
     * JSONObject.
     * @return A JSONArray containing the key strings, or null if the JSONObject
     * is empty.
     */
    public JSONArray names() {
        JSONArray ja = new JSONArray();
        Iterator  keys = keys();
        while (keys.hasNext()) {
            ja.put(keys.next());
        }
        if (ja.length() == 0) {
            return null;
        }
        return ja;
    }


    /**
     * Produce a string from a number.
     * @exception ArithmeticException JSON can only serialize finite numbers.
     * @param  n A Number
     * @return A String.
     */
    static public String numberToString(Number n) throws ArithmeticException {
        if (
                (n instanceof Float &&
                    (((Float)n).isInfinite() || ((Float)n).isNaN())) ||
                (n instanceof Double &&
                    (((Double)n).isInfinite() || ((Double)n).isNaN()))) {
            throw new ArithmeticException(
                "JSON can only serialize finite numbers.");
        }

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

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