JSONWriter.java

//package org.stringtree.json;

import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.text.CharacterIterator;
import java.text.StringCharacterIterator;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Stack;

public class JSONWriter {

    private StringBuffer buf = new StringBuffer();
    private Stack<Object> calls = new Stack<Object>();
    boolean emitClassName = true;
    
    public JSONWriter(boolean emitClassName) {
        this.emitClassName = emitClassName;
    }
    
    public JSONWriter() {
        this(true);
    }

    public String write(Object object) {
        buf.setLength(0);
        value(object);
        return buf.toString();
    }

    public String write(long n) {
        return String.valueOf(n);
    }

    public String write(double d) {
        return String.valueOf(d);
    }

    public String write(char c) {
        return "\"" + c + "\"";
    }
    
    public String write(boolean b) {
        return String.valueOf(b);
    }

    @SuppressWarnings("unchecked")
	private void value(Object object) {
        if (object == null || cyclic(object)) {
            add("null");
        } else {
            calls.push(object);
            if (object instanceof Class) string(object);
            else if (object instanceof Boolean) bool(((Boolean) object).booleanValue());
            else if (object instanceof Number) add(object);
            else if (object instanceof String) string(object);
            else if (object instanceof Character) string(object);
            else if (object instanceof Map) map((Map)object);
            else if (object.getClass().isArray()) array(object);
            else if (object instanceof Iterator) array((Iterator)object);
            else if (object instanceof Collection) array(((Collection)object).iterator());
            else if (object instanceof JSONSerializable) value(((JSONSerializable)object).jsonSerialize());
            else bean(object);
            calls.pop();
        }
    }

    private boolean cyclic(Object object) {
        Iterator<Object> it = calls.iterator();
        while (it.hasNext()) {
            Object called = it.next();
            if (object == called) return true;
        }
        return false;
    }
    
    private void bean(Object object) {
        add("{");
        BeanInfo info;
        boolean addedSomething = false;
        try {
            info = Introspector.getBeanInfo(object.getClass());
            PropertyDescriptor[] props = info.getPropertyDescriptors();
            for (int i = 0; i < props.length; ++i) {
                PropertyDescriptor prop = props[i];
                String name = prop.getName();
                Method accessor = prop.getReadMethod();
                if ((emitClassName==true || !"class".equals(name)) && accessor != null) {
                    if (!accessor.isAccessible()) accessor.setAccessible(true);
                    Object value = accessor.invoke(object, (Object[])null);
                    if (addedSomething) add(',');
                    add(name, value);
                    addedSomething = true;
                }
            }
            Field[] ff = object.getClass().getFields();
            for (int i = 0; i < ff.length; ++i) {
                Field field = ff[i];
                if (addedSomething) add(',');
                add(field.getName(), field.get(object));
                addedSomething = true;
            }
        } catch (IllegalAccessException iae) {
            iae.printStackTrace();
        } catch (InvocationTargetException ite) {
            ite.getCause().printStackTrace();
            ite.printStackTrace();
        } catch (IntrospectionException ie) {
            ie.printStackTrace();
        } 
        add("}");
    }

    private void add(String name, Object value) {
        add('"');
        add(name);
        add("\":");
        value(value);
    }

    private void map(Map<String,Object> map) {
        add("{");
        Iterator<Map.Entry<String,Object>> it = map.entrySet().iterator();
        while (it.hasNext()) {
            Map.Entry<?,?> e = (Map.Entry<?,?>) it.next();
            value(e.getKey());
            add(":");
            value(e.getValue());
            if (it.hasNext()) add(',');
        }
        add("}");
    }
    
    private void array(Iterator<?> it) {
        add("[");
        while (it.hasNext()) {
            value(it.next());
            if (it.hasNext()) add(",");
        }
        add("]");
    }

    private void array(Object object) {
        add("[");
        int length = Array.getLength(object);
        for (int i = 0; i < length; ++i) {
            value(Array.get(object, i));
            if (i < length - 1) add(',');
        }
        add("]");
    }

    private void bool(boolean b) {
        add(b ? "true" : "false");
    }

    private void string(Object obj) {
        add('"');
        CharacterIterator it = new StringCharacterIterator(obj.toString());
        for (char c = it.first(); c != CharacterIterator.DONE; c = it.next()) {
            if (c == '"') add("\\\"");
            else if (c == '\\') add("\\\\");
            else if (c == '/') add("\\/");
            else if (c == '\b') add("\\b");
            else if (c == '\f') add("\\f");
            else if (c == '\n') add("\\n");
            else if (c == '\r') add("\\r");
            else if (c == '\t') add("\\t");
            else if (Character.isISOControl(c)) {
                unicode(c);
            } else {
                add(c);
            }
        }
        add('"');
    }

    private void add(Object obj) {
        buf.append(obj);
    }

    private void add(char c) {
        buf.append(c);
    }

    static char[] hex = "0123456789ABCDEF".toCharArray();

    private void unicode(char c) {
        add("\\u");
        int n = c;
        for (int i = 0; i < 4; ++i) {
            int digit = (n & 0xf000) >> 12;
            add(hex[digit]);
            n <<= 4;
        }
    }
}