java和json相互转换

1.把java 对象列表转换为json对象数组，并转为字符串

   JSONArray array = JSONArray.fromObject(userlist);
    String jsonstr = array.toString();

 

2.把java对象转换成json对象，并转化为字符串JSONObject object = JSONObject.fromObject(invite);

3.把JSON字符串转换为JAVA 对象数组

String personstr = getRequest().getParameter("persons");
  JSONArray json = JSONArray.fromObject(personstr);
  List<InvoidPerson> persons = (List<InvoidPerson>)JSONArray.toCollection(json, nvoidPerson.class);

4.把JSON字符串转换为JAVA 对象

5.把JSON字符串转换为Json对象

 

public  class  Demo {
    public  static  void  main(String[] args)  throws  Exception {
        String str =  "{\"brand_no\":\"jycy,sy\",\"unit_rank\":\"2\",\"package\":\"2\"}" ;
        JSONObject obj =  new  JSONObject(str);
        System.out.println(obj);
        System.out.println(obj.get( "brand_no" ));  // "jycy,sy"
    }
}