JSON 字符串 与 java 对象之间互相转换

首先引入maven需要依赖的jar：

<dependency>
    <groupId>net.sf.json-libgroupId>
    <artifactId>json-libartifactId>
    <version>2.4version>
    <classifier>jdk15classifier>
dependency>

需要导入的类：

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

    JSONArrayarray = JSONArray.fromObject(userlist);     Stringjsonstr = 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);   Listpersons =(List)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\"}]}";    JSONObjectjsonobject = JSONObject.fromObject(str);   PassportLendsEntitypassportlends = null;   try {    //获取一个json数组    JSONArrayarray = jsonobject.getJSONArray("passports");    //将json数组 转换成List泛型    Listlist = newArrayList();    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);

5.如果只想取JSON字符串的某几个字段，就没必要转成Java对象，直接转成对象数组，再把数组转成对象，再去某个字段的值

JSONArray listArray = dataObject.getJSONArray("list");
for (int i =0; i < listArray.size(); i++){
    tmp = listArray.getJSONObject(i);
    float longitude = tmp.getString("longitude");

}