// 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);