JAVA对象JSON数据互相转换的常见情况

1.java对象转成Json数组

JSONArray array=JSONArray.fromObject(javaobject);

将array转成字符串:String  jsonstr=array.toString();

2.java对象转成Json对象

JSONObject jsonobject=JSONObject.fromObject(javaobject);

将jsonobject转成字符串:jsonobject.toString();

3.Json字符串转成java对象数组

String personstr=getRequest().getParameter("personstr");

JSONArray json=JSONArray.fromObject(personstr);

List<Person> persons=(List<Person> )JSONArray.toCollection(json,Person.class);

4.Json字符串转成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\"}]}";