jsonarray.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.io.IOException;
import java.io.Writer;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Map;

/**
 * A JSONArray is an ordered sequence of values. Its external text form is a
 * string wrapped in square brackets with commas separating the values. The
 * internal form is an object having <code>get</code> and <code>opt</code>
 * methods for accessing the values by index, and <code>put</code> methods for
 * adding or replacing values. 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 object</code>.
 * <p>
 * The constructor can convert a JSON text into a Java object. The
 * <code>toString</code> method converts to JSON text.
 * <p>
 * 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 texts produced by the <code>toString</code> methods strictly conform to
 * JSON syntax 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 bracket.</li>
 * <li>The <code>null</code> value will be inserted when there
 *     is <code>,</code>&nbsp;<small>(comma)</small> elision.</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>Values can be separated 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 JSONArray {


    /**
     * The arrayList where the JSONArray's properties are kept.
     */
    private ArrayList myArrayList;


    /**
     * Construct an empty JSONArray.
     */
    public JSONArray() {
        this.myArrayList = new ArrayList();
    }

    /**
     * Construct a JSONArray from a JSONTokener.
     * @param x A JSONTokener
     * @throws JSONException If there is a syntax error.
     */
    public JSONArray(JSONTokener x) throws JSONException {
        this();
        if (x.nextClean() != '[') {
            throw x.syntaxError("A JSONArray text must start with '['");
        }
        if (x.nextClean() == ']') {
            return;
        }
        x.back();
        for (;;) {
            if (x.nextClean() == ',') {
                x.back();
                this.myArrayList.add(null);
            } else {
                x.back();
                this.myArrayList.add(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 JSONArray from a source sJSON text.
     * @param string     A string that begins with
     * <code>[</code>&nbsp;<small>(left bracket)</small>
     *  and ends with <code>]</code>&nbsp;<small>(right bracket)</small>.
     *  @throws JSONException If there is a syntax error.
     */
    public JSONArray(String string) throws JSONException {
        this(new JSONTokener(string));
    }


    /**
     * Construct a JSONArray from a Collection.
     * @param collection     A Collection.
     */
    public JSONArray(Collection collection) {
        this.myArrayList = (collection == null) ?
        	new ArrayList() :
	        new ArrayList(collection);
    }


    /**
     * Get the object value associated with an index.
     * @param index
     *  The index must be between 0 and length() - 1.
     * @return An object value.
     * @throws JSONException If there is no value for the index.
     */
    public Object get(int index) throws JSONException {
        Object o = opt(index);
        if (o == null) {
            throw new JSONException("JSONArray[" + index + "] not found.");
        }
        return o;
    }


    /**
     * Get the boolean value associated with an index.
     * The string values "true" and "false" are converted to boolean.
     *
     * @param index The index must be between 0 and length() - 1.
     * @return      The truth.
     * @throws JSONException If there is no value for the index or if the
     *  value is not convertable to boolean.
     */
    public boolean getBoolean(int index) throws JSONException {
        Object o = get(index);
        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("JSONArray[" + index + "] is not a Boolean.");
    }


    /**
     * Get the double value associated with an index.
     *
     * @param index The index must be between 0 and length() - 1.
     * @return      The value.
     * @throws   JSONException If the key is not found or if the value cannot
     *  be converted to a number.
     */
    public double getDouble(int index) throws JSONException {
        Object o = get(index);
        try {
            return o instanceof Number ?
                ((Number)o).doubleValue() : 
                Double.valueOf((String)o).doubleValue();
        } catch (Exception e) {
            throw new JSONException("JSONArray[" + index +
                "] is not a number.");
        }
    }


    /**
     * Get the int value associated with an index.
     *
     * @param index The index must be between 0 and length() - 1.
     * @return      The value.
     * @throws   JSONException If the key is not found or if the value cannot
     *  be converted to a number.
     *  if the value cannot be converted to a number.
     */
    public int getInt(int index) throws JSONException {
        Object o = get(index);
        return o instanceof Number ?
                ((Number)o).intValue() : (int)getDouble(index);
    }


    /**
     * Get the JSONArray associated with an index.
     * @param index The index must be between 0 and length() - 1.
     * @return      A JSONArray value.
     * @throws JSONException If there is no value for the index. or if the
     * value is not a JSONArray
     */
    public JSONArray getJSONArray(int index) throws JSONException {
        Object o = get(index);
        if (o instanceof JSONArray) {
            return (JSONArray)o;
        }
        throw new JSONException("JSONArray[" + index +
                "] is not a JSONArray.");
    }


    /**
     * Get the JSONObject associated with an index.
     * @param index subscript
     * @return      A JSONObject value.
     * @throws JSONException If there is no value for the index or if the
     * value is not a JSONObject
     */
    public JSONObject getJSONObject(int index) throws JSONException {
        Object o = get(index);
        if (o instanceof JSONObject) {
            return (JSONObject)o;
        }
        throw new JSONException("JSONArray[" + index +
            "] is not a JSONObject.");
    }


    /**
     * Get the long value associated with an index.
     *
     * @param index The index must be between 0 and length() - 1.
     * @return      The value.
     * @throws   JSONException If the key is not found or if the value cannot
     *  be converted to a number.
     */
    public long getLong(int index) throws JSONException {
        Object o = get(index);
        return o instanceof Number ?
                ((Number)o).longValue() : (long)getDouble(index);
    }


    /**
     * Get the string associated with an index.
     * @param index The index must be between 0 and length() - 1.
     * @return      A string value.
     * @throws JSONException If there is no value for the index.
     */
    public String getString(int index) throws JSONException {
        return get(index).toString();
    }


    /**
     * Determine if the value is null.
     * @param index The index must be between 0 and length() - 1.
     * @return true if the value at the index is null, or if there is no value.
     */
    public boolean isNull(int index) {
        return JSONObject.NULL.equals(opt(index));
    }


    /**
     * Make a string from the contents of this JSONArray. The
     * <code>separator</code> string is inserted between each element.
     * Warning: This method assumes that the data structure is acyclical.
     * @param separator A string that will be inserted between the elements.
     * @return a string.
     * @throws JSONException If the array contains an invalid number.
     */
    public String join(String separator) throws JSONException {
        int len = length();
        StringBuffer sb = new StringBuffer();

        for (int i = 0; i < len; i += 1) {
            if (i > 0) {
                sb.append(separator);
            }
            sb.append(JSONObject.valueToString(this.myArrayList.get(i)));
        }
        return sb.toString();
    }


    /**
     * Get the number of elements in the JSONArray, included nulls.
     *
     * @return The length (or size).
     */
    public int length() {
        return this.myArrayList.size();
    }


    /**
     * Get the optional object value associated with an index.
     * @param index The index must be between 0 and length() - 1.
     * @return      An object value, or null if there is no
     *              object at that index.
     */
    public Object opt(int index) {
        return (index < 0 || index >= length()) ?
            null : this.myArrayList.get(index);
    }


    /**
     * Get the optional boolean value associated with an index.
     * It returns false if there is no value at that index,
     * or if the value is not Boolean.TRUE or the String "true".
     *
     * @param index The index must be between 0 and length() - 1.
     * @return      The truth.
     */
    public boolean optBoolean(int index)  {
        return optBoolean(index, false);
    }


    /**
     * Get the optional boolean value associated with an index.
     * It returns the defaultValue if there is no value at that index or if
     * it is not a Boolean or the String "true" or "false" (case insensitive).
     *
     * @param index The index must be between 0 and length() - 1.
     * @param defaultValue     A boolean default.
     * @return      The truth.
     */
    public boolean optBoolean(int index, boolean defaultValue)  {
        try {
            return getBoolean(index);
        } catch (Exception e) {
            return defaultValue;
        }
    }


    /**
     * Get the optional double value associated with an index.
     * NaN is returned if there is no value for the index,
     * or if the value is not a number and cannot be converted to a number.
     *
     * @param index The index must be between 0 and length() - 1.
     * @return      The value.
     */
    public double optDouble(int index) {
        return optDouble(index, Double.NaN);
    }


    /**
     * Get the optional double value associated with an index.
     * The defaultValue is returned if there is no value for the index,
     * or if the value is not a number and cannot be converted to a number.
     *
     * @param index subscript
     * @param defaultValue     The default value.
     * @return      The value.
     */
    public double optDouble(int index, double defaultValue) {
        try {
            return getDouble(index);
        } catch (Exception e) {
            return defaultValue;
        }
    }


    /**
     * Get the optional int value associated with an index.
     * Zero is returned if there is no value for the index,
     * or if the value is not a number and cannot be converted to a number.
     *
     * @param index The index must be between 0 and length() - 1.
     * @return      The value.
     */
    public int optInt(int index) {
        return optInt(index, 0);
    }


    /**
     * Get the optional int value associated with an index.
     * The defaultValue is returned if there is no value for the index,
     * or if the value is not a number and cannot be converted to a number.
     * @param index The index must be between 0 and length() - 1.
     * @param defaultValue     The default value.
     * @return      The value.
     */
    public int optInt(int index, int defaultValue) {
        try {