1.从Object到String

要先用Object对象构造一个JSONObject或者JSONArray对象，然后调用它的toString()方法即可

（1）示例一

Book book=new Book();
book.setName("Java");
book.setPrice(52.3f);
JSONObject object=JSONObject.fromObject(book);
System.out.println(object.toString());

Book book=new Book();
        book.setName("Java");
        book.setPrice(52.3f);
        
        Book book2=new Book();
        book2.setName("C");
        book2.setPrice(42.3f);
        List list=new ArrayList();
        list.add(book);
        list.add(book2);
        JSONArray arry=JSONArray.fromObject(list);
        System.out.println(arry.toString());
//结果如下：
[{"name":"Java","price":52.3},{"name":"C","price":42.3}]

2.从String到Object要先用String对象构造一个JSONObject或者JSONArray对象

(1)示例一

String json="{name:'Java',price:52.3}";    
JSONObject object=JSONObject.fromObject(json);
System.out.println(object.get("name")+" "+object.get("price"));

String json="[{name:'Java',price:52.3},{name:'C',price:42.3}]";
JSONArray array=JSONArray.fromObject(json);
 for(int i=0;i<array.size();i++){
     Map o=(Map)array.get(i);
     System.out.println(o.get("name")+" "+o.get("price"));
 }

String json="{name:'Java',price:52.3}";
JSONObject object=JSONObject.fromObject(json);
Product product=(Product)JSONObject.toBean(object,Product.class);
System.out.println(product.getName()+" "+product.getPrice());

String json="[{name:'Java',price:42.3}]";
JSONArray array=JSONArray.fromObject(json);
Product[] products=(Product[]) JSONArray.toArray(array,Product.class);
 for(Product p:products){
 System.out.println(p.getName()+" "+p.getPrice());
 }

package com.util;

import java.util.List;
import java.util.Map;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

public class JsonHelper {
    //从普通的Bean转换为字符串
    public static String getJson(Object o){
        JSONObject jo=JSONObject.fromObject(o);
        return jo.toString();
    }
    //从Java的列表转换为字符串
    public static String getJson(List list){
        JSONArray ja=JSONArray.fromObject(list);
        return ja.toString();
    }
    //从Java对象数组转换为字符串
    public static String getJson(Object[] arry){
        JSONArray ja=JSONArray.fromObject(arry);
        return ja.toString();
    }
    //从json格式的字符串转换为Map对象
    public static Map getObject(String s){
        return     JSONObject.fromObject(s);
    }
    //从json格式的字符串转换为List数组
    public static List getArray(String s){
        return JSONArray.fromObject(s);
    }
    //从json格式的字符串转换为某个Bean
    public static Object getObject(String s,Class cls){
        JSONObject jo=JSONObject.fromObject(s);
        return JSONObject.toBean(jo,cls);
    }
    //从json格式的字符串转换为某类对象的数组
    public static Object getArray(String s,Class cls){
        JSONArray ja=JSONArray.fromObject(s);
        return JSONArray.toArray(ja,cls);
    }
}