常用的java类型转json的转换类

package com.pz.util;


import java.lang.reflect.Field;
import java.util.Date;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

public class JsonObjectConvert {
    
    private StringBuffer sf = null;
    
    
    public  String SimpleObjectToJson(Object o){
        
        sf = new StringBuffer("{");
        
        
        //sf.append(o.getClass().getSimpleName());
        Field field[] = o.getClass().getDeclaredFields();
        String content = "";
        for(Field f : field ){
            try {
                f.setAccessible(true);
                content += "\"" + f.getName() + "\":\"" + convertNull(f.get(o)) +"\",";
            } catch (IllegalArgumentException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        sf.append(content);
        return sf.toString().substring(0, sf.length() - 1) + "}";
    }
    public Object convertNull(Object o){
        if(o == null){
            return "";
        }else {
            return o;
        }
    }
    @SuppressWarnings("unchecked")
    public  Object convertJSON(Object o){
        if(o == null){
            return "";
        }else if(o instanceof Boolean){
            return "\"" +o.toString() + "\"";
        }else if(o instanceof Character){
            return "\"" +o.toString() + "\"";
        }else if(o instanceof Short){
            return "\"" +o.toString() + "\"";
        }else if(o instanceof Integer){
            return "\"" +o.toString() + "\"";
        }else if(o instanceof Long){
            return "\"" +o.toString() + "\"";
        }else if(o instanceof Float){
            return "\"" +o.toString() + "\"";
        }else if(o instanceof Double){
            return "\"" +o.toString() + "\"";
        }else if(o instanceof Byte){
            return "\"" +o.toString() + "\"";
        }else if(o instanceof List){
            return listToJSON((List)o);
        }else if(o instanceof Map){
            return mapToJSON((Map)o);
        }else if(o.getClass().isArray()){
            return arrayToJSON(o);
        }else if(o instanceof String){
            return "\"" +o.toString() + "\"";
        }else if(o instanceof Date){
            return "\"" +o.toString() + "\"";
        }
        return SimpleObjectToJson(o);
    }
    @SuppressWarnings("unchecked")
    public  String listToJSON(List list){
        sf = new StringBuffer("[");
        for(int i = 0;i < list.size();i++){
            sf.append( convertJSON(list.get(i)) + ",");
        }
        return sf.toString().substring(0,sf.toString().length() - 1) + "]";
    }
    @SuppressWarnings("unchecked")
    public  String mapToJSON(Map map){
        sf = new StringBuffer("[");
        Iterator ite = map.entrySet().iterator();
        while(ite.hasNext()){
            Entry o = (Entry)ite.next();
            String key = convertJSON(o.getKey()).toString();
            sf.append("{\"" + key.substring(1, key.length() - 1) + "\":");
            sf.append(convertJSON(o.getValue()) +"},");
        }
        return sf.toString().substring(0,sf.toString().length() - 1) + "]";
    }
    public String arrayToJSON(Object o){
        sf = new StringBuffer("[");
        Object[] obj = (Object[])o;
        for(int i = 0;i < obj.length;i++){
            sf.append(convertJSON(obj[i]) + ",");
        }
        return sf.toString().substring(0, sf.toString().length() - 1) + "]";
    }
    //the sum method convert to json key --> value
    public static String putJSON(String key,Object value){
        JsonObjectConvert joc = new JsonObjectConvert();
        String jsonString = "{\"" + key + "\":" + joc.convertJSON(value) + "}"; 
        return jsonString;
    }
}