JAVA对象JSON数据互相转换的四种常见情况

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);
   String str=object.toString());

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

 JSONObject jsonobject = JSONObject.fromObject(str);
  PassportLendsEntity passportlends = null;
  try {
   //获取一个json数组
   JSONArray array = jsonobject.getJSONArray("passports");
   //将json数组 转换成 List<PassPortForLendsEntity>泛型
   List<PassPortForLendsEntity> list = new ArrayList<PassPortForLendsEntity>();
   for (int i = 0; i < array.size(); i++) {   
            JSONObject object = (JSONObject)array.get(i);  
            PassPortForLendsEntity passport = (PassPortForLendsEntity)JSONObject.toBean(object,
              PassPortForLendsEntity.class);
            if(passport != null){
             list.add(passport);
            }  
     }
   //转换PassportLendsEntity 实体类
  passportlends = (PassportLendsEntity)JSONObject.toBean(jsonobject, PassportLendsEntity.class);

  str = "{"lendperson":"李四","lendcompany":"有限公司","checkperson":"李四",

  "lenddate":"2010-07-19T00:00:00","lendcounts":4,"
  passports":[{"passportid":"d","name":"李豫川","passporttype":"K"},
  {"passportid":"K9051","name":"李平","passporttype":"K"},
  {"passportid":"K90517","name":"袁寒梅","passporttype":"K"},
  {"passportid":"K905199","name":"贺明","passporttype":"K"}]}";