JSON和java对象的互转

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准备工作：

（1）普通JSON转换

引入相应的包

json-lib-2.2-jdk15.jar

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

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);
Log4jInit.ysulogger.debug(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

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\"}]}";
   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);

（2）fastJson使用

1.JSON jsonObj= JSON.parse(" {"name":"lucy"}");

字符串转化为JSON对象

2.JSONArray ja= JSON.parseArray("{"name":"lucy";"age":"16"}");

字符串转化为json数组

3.1.String转化为JSON对象
JSON json=JSON.parseObject("{"name":"jack"}");
2.JSON对象转化为JAVA对象
User user=JSON.toJavaObject(json, User.class);
3.JAVA对象解析为String形式。

4.JSON转化为Java对象数组

List<User> userList= JSON.parseArray("{"name":lucy;age:17}", User.class)

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