json.java

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//========================================================================
//Copyright 2004-2008 Mort Bay Consulting Pty. Ltd.
//------------------------------------------------------------------------
//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 org.mortbay.util.ajax;

import java.io.Externalizable;
import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.lang.reflect.Array;
import java.lang.reflect.Constructor;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import org.mortbay.log.Log;
import org.mortbay.util.IO;
import org.mortbay.util.Loader;
import org.mortbay.util.QuotedStringTokenizer;
import org.mortbay.util.TypeUtil;

/** JSON Parser and Generator.
 * 
 * <p>This class provides some static methods to convert POJOs to and from JSON
 * notation.  The mapping from JSON to java is:<pre>
 *   object ==> Map
 *   array  ==> Object[]
 *   number ==> Double or Long
 *   string ==> String
 *   null   ==> null
 *   bool   ==> Boolean
 * </pre>
 * </p><p>
 * The java to JSON mapping is:<pre>
 *   String --> string
 *   Number --> number
 *   Map    --> object
 *   List   --> array
 *   Array  --> array
 *   null   --> null
 *   Boolean--> boolean
 *   Object --> string (dubious!)
 * </pre>
 * </p><p>
 * The interface {@link JSON.Convertible} may be implemented by classes that wish to externalize and 
 * initialize specific fields to and from JSON objects.  Only directed acyclic graphs of objects are supported.
 * </p>
 * <p>
 * The interface {@link JSON.Generator} may be implemented by classes that know how to render themselves as JSON and
 * the {@link #toString(Object)} method will use {@link JSON.Generator#addJSON(StringBuffer)} to generate the JSON.
 * The class {@link JSON.Literal} may be used to hold pre-gnerated JSON object. 
 * <p>
 * The interface {@link Convertor} may be implemented to provide static convertors for objects that may be registered 
 * with {@link #registerConvertor(Class, org.mortbay.util.ajax.JSON.Convertor)}. These convertors are looked up by class, interface and
 * super class by {@link #getConvertor(Class)}.
 * </p>
 * @author gregw
 *
 */
public class JSON
{
    private static JSON __default = new JSON();

    private Map _convertors=new HashMap();
    private int _stringBufferSize=256;
    
    
    public JSON()
    {
    }
    
    /* ------------------------------------------------------------ */
    /**
     * @return the initial stringBuffer size to use when creating JSON strings (default 256)
     */
    public int getStringBufferSize()
    {
        return _stringBufferSize;
    }



    /* ------------------------------------------------------------ */
    /**
     * @param stringBufferSize the initial stringBuffer size to use when creating JSON strings (default 256)
     */
    public void setStringBufferSize(int stringBufferSize)
    {
        _stringBufferSize=stringBufferSize;
    }
    



    /**
     * Register a {@link Convertor} for a class or interface.
     * @param forClass The class or interface that the convertor applies to
     * @param convertor the convertor
     */
    public static void registerConvertor(Class forClass, Convertor convertor)
    {
        __default.addConvertor(forClass,convertor);
    }

    public static JSON getDefault()
    {
        return __default;
    }

    public static void setDefault(JSON json)
    {
        __default=json;
    }
    
    public static String toString(Object object)
    {
        StringBuffer buffer=new StringBuffer(__default.getStringBufferSize());
        synchronized (buffer)
        {
            __default.append(buffer,object);
            return buffer.toString();
        }
    }

    public static String toString(Map object)
    {
        StringBuffer buffer=new StringBuffer(__default.getStringBufferSize());
        synchronized (buffer)
        {
            __default.appendMap(buffer,object);
            return buffer.toString();
        }
    }

    public static String toString(Object[] array)
    {
        StringBuffer buffer=new StringBuffer(__default.getStringBufferSize());
        synchronized (buffer)
        {
            __default.appendArray(buffer,array);
            return buffer.toString();
        }
    }

    /**
     * @param s String containing JSON object or array.
     * @return A Map, Object array or primitive array parsed from the JSON.
     */
    public static Object parse(String s)
    {
        return __default.parse(new StringSource(s),false);
    }

    /**
     * @param s String containing JSON object or array.
     * @param stripOuterComment If true, an outer comment around the JSON is ignored.
     * @return A Map, Object array or primitive array parsed from the JSON.
     */
    public static Object parse(String s, boolean stripOuterComment)
    {
        return __default.parse(new StringSource(s),stripOuterComment);
    }

    /**
     * @param in Reader containing JSON object or array.
     * @return A Map, Object array or primitive array parsed from the JSON.
     */
    public static Object parse(Reader in) throws IOException
    {
        return __default.parse(new ReaderSource(in),false);
    }

    /**
     * @param s Stream containing JSON object or array.
     * @param stripOuterComment If true, an outer comment around the JSON is ignored.
     * @return A Map, Object array or primitive array parsed from the JSON.
     */
    public static Object parse(Reader in, boolean stripOuterComment) throws IOException
    {
        return __default.parse(new ReaderSource(in),stripOuterComment);
    }

    /**
     * @deprecated use {@link #parse(Reader)}
     * @param in Reader containing JSON object or array.
     * @return A Map, Object array or primitive array parsed from the JSON.
     */
    public static Object parse(InputStream in) throws IOException
    {
        return __default.parse(new StringSource(IO.toString(in)),false);
    }

    /**
     * @deprecated use {@link #parse(Reader, boolean)}
     * @param s Stream containing JSON object or array.
     * @param stripOuterComment If true, an outer comment around the JSON is ignored.
     * @return A Map, Object array or primitive array parsed from the JSON.
     */
    public static Object parse(InputStream in, boolean stripOuterComment) throws IOException
    {
        return __default.parse(new StringSource(IO.toString(in)),stripOuterComment);
    }

    /* ------------------------------------------------------------ */
    /** Convert Object to JSON
     * @param object The object to convert
     * @return The JSON String
     */
    public String toJSON(Object object)
    {
        StringBuffer buffer=new StringBuffer(getStringBufferSize());
        synchronized (buffer)
        {
            append(buffer,object);
            return buffer.toString();
        }
    }

    /* ------------------------------------------------------------ */
    /** Convert JSON to Object
     * @param json The json to convert
     * @return The object
     */
    public Object fromJSON(String json)
    {
        Source source = new StringSource(json);
        return parse(source);
    }
    
    /**
     * Append object as JSON to string buffer.
     * @param buffer
     * @param object
     */
    public void append(StringBuffer buffer, Object object)
    {
        if (object==null)
            buffer.append("null");
        else if (object instanceof Convertible)
            appendJSON(buffer,(Convertible)object);
        else if (object instanceof Generator)
            appendJSON(buffer,(Generator)object);
        else if (object instanceof Map)
            appendMap(buffer,(Map)object);
        else if (object instanceof Collection)
            appendArray(buffer,(Collection)object);
        else if (object.getClass().isArray())
            appendArray(buffer,object);
        else if (object instanceof Number)
            appendNumber(buffer,(Number)object);
        else if (object instanceof Boolean)
            appendBoolean(buffer,(Boolean)object);
        else if (object instanceof String)
            appendString(buffer,(String)object);
        else
        {
            Convertor convertor=getConvertor(object.getClass());
            if (convertor!=null)
                appendJSON(buffer,convertor,object);
            else
                appendString(buffer,object.toString());
        }
    }

    public void appendNull(StringBuffer buffer)
    {
        buffer.append("null");
    }

    public void appendJSON(final StringBuffer buffer, final Convertor convertor, final Object object)
    {
        appendJSON(buffer,new Convertible()
        {
            public void fromJSON(Map object)
            {
            }

            public void toJSON(Output out)
            {
                convertor.toJSON(object,out);
            }
        });
    }

    public void appendJSON(final StringBuffer buffer, Convertible converter)
    {
        final char[] c=
        { '{' };
        converter.toJSON(new Output()
        {
            public void add(Object obj)
            {
                if (c[0]==0)
                    throw new IllegalStateException();
                append(buffer,obj);
                c[0]=0;
            }

            public void addClass(Class type)
            {
                if (c[0]==0)
                    throw new IllegalStateException();
                buffer.append(c);
                buffer.append("\"class\":");
                append(buffer,type.getName());
                c[0]=',';
            }

            public void add(String name, Object value)
            {
                if (c[0]==0)
                    throw new IllegalStateException();
                buffer.append(c);
                QuotedStringTokenizer.quote(buffer,name);
                buffer.append(':');
                append(buffer,value);
                c[0]=',';
            }

            public void add(String name, double value)
            {
                if (c[0]==0)
                    throw new IllegalStateException();
                buffer.append(c);
                QuotedStringTokenizer.quote(buffer,name);
                buffer.append(':');
                appendNumber(buffer,new Double(value));
                c[0]=',';
            }

            public void add(String name, long value)
            {
                if (c[0]==0)
                    throw new IllegalStateException();
                buffer.append(c);
                QuotedStringTokenizer.quote(buffer,name);
                buffer.append(':');
                appendNumber(buffer,TypeUtil.newLong(value));
                c[0]=',';
            }

            public void add(String name, boolean value)
            {
                if (c[0]==0)
                    throw new IllegalStateException();
                buffer.append(c);
                QuotedStringTokenizer.quote(buffer,name);
                buffer.append(':');
                appendBoolean(buffer,value?Boolean.TRUE:Boolean.FALSE);
                c[0]=',';
            }
        });

        if (c[0]=='{')
            buffer.append("{}");
        else if (c[0]!=0)
            buffer.append("}");
    }

    public void appendJSON(StringBuffer buffer, Generator generator)
    {
        generator.addJSON(buffer);
    }

    public void appendMap(StringBuffer buffer, Map object)
    {
        if (object==null)
        {
            appendNull(buffer);
            return;
        }

        buffer.append('{');
        Iterator iter=object.entrySet().iterator();
        while (iter.hasNext())
        {
            Map.Entry entry=(Map.Entry)iter.next();
            QuotedStringTokenizer.quote(buffer,entry.getKey().toString());
            buffer.append(':');
            append(buffer,entry.getValue());
            if (iter.hasNext())
                buffer.append(',');
        }

        buffer.append('}');
    }

    public void appendArray(StringBuffer buffer, Collection collection)
    {
        if (collection==null)
        {
            appendNull(buffer);
            return;
        }

        buffer.append('[');
        Iterator iter=collection.iterator();
        boolean first=true;
        while (iter.hasNext())
        {
            if (!first)
                buffer.append(',');

            first=false;
            append(buffer,iter.next());
        }

        buffer.append(']');
    }

    public void appendArray(StringBuffer buffer, Object array)
    {
        if (array==null)
        {
            appendNull(buffer);
            return;
        }

        buffer.append('[');
        int length=Array.getLength(array);

        for (int i=0; i<length; i++)
        {
            if (i!=0)
                buffer.append(',');
            append(buffer,Array.get(array,i));
        }

        buffer.append(']');
    }

    public void appendBoolean(StringBuffer buffer, Boolean b)
    {
        if (b==null)
        {
            appendNull(buffer);
            return;
        }
        buffer.append(b.booleanValue()?"true":"false");
    }

    public void appendNumber(StringBuffer buffer, Number number)
    {
        if (number==null)
        {
            appendNull(buffer);
            return;
        }