JSON简介及JSONObject生成json

1、JSON简介

JSON:JavaScript对象表示法（JavaScript Object Notation）

相似xml  :存储和交换信息的语法

比xml更快、更易解析

JSON语法规则：

　　一、数据在名称/值对中

　　二、数据有逗号分隔

　　三、花括号保存对象

　　四、方括号保存数组

JSON值：

　　一、数字：整数或浮点数

　　二、字符串：在双引号中

　　三、逻辑值：true false

　　四、数组：在方括号中

　　五、对象：在花括号中

　　六、null

2、在JAVA中使用JSONObject生成json

所须要的包

commons-httpclient-3.1.jar

commons-lang-2.4.jar

commons-logging-1.1.1.jar

json-lib-2.4-jdk15.jar

ezmorph-1.0.6.jar

commons-collections-3.2.1.jar

 一、bean转为Json

 

User u = new User();
u.setAge(22);
u.setUsername("hzucmj");
u.setEnabled(true);
 
JSONObject json = JSONObject.fromObject(u);
System.out.println(json.toString()); //结果为：{"enabled":true,"username":"hzucmj","age":22}

二、List转为Json

 

User u1 = new User();
u1.setAge(22);
u1.setUsername("hzucmj");
u1.setEnabled(true);
 
User u2 = new User();
u2.setAge(20);
u2.setUsername("ctf");
u2.setEnabled(true);
 
List<Object> list = new ArrayList<Object>();
list.add(u1);</p>
list.add(u2);</p>
 
JSONArray json = JSONArray.fromObject(list);
System.out.println(json.toString()); //结果为：[{"enabled":false,"username":"ctf","age":20},{"enabled":false,"username":"","age":0}]

三、Map转为Json

HashMap<String, Comparable> map = new HashMap<String, Comparable>();
map.put("name", "hzucmj");
map.put("age", 22);
JSONObject json = JSONObject.fromObject(map);
System.out.println(json.toString()); //结果为：{"name":"hzucmj","age":22}


3、JSON转换的四种各类状况：

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\"}]}";

 本文部分转载至：http://blog.csdn.net/ygzk123/article/details/8273293

http://www.cnblogs.com/xwdreamer/archive/2011/12/16/2296904.html