主流JSON库使用示例

Catalogue

1. 1. Jackson
2. 2. FastJSON
3. 3. GSON
4. 4. 参考资料

Jackson

1. 对象转json

private ObjectMapper mapper = new ObjectMapper();
   
   @Test
   public void testJson() throws JsonProcessingException {
       User user = new User();
       user.setId(8L);
       user.setAge(21);
       user.setName("柳岩");
       user.setUserName("liuyan");
       // 序列化
       String json = mapper.writeValueAsString(user);
       System.out.println("json = " + json);
   }

2. json转普通对象

private ObjectMapper mapper = new ObjectMapper();

@Test
public void testJson() throws IOException {
    User user = new User();
    user.setId(8L);
    user.setAge(21);
    user.setName("柳岩");
    user.setUserName("liuyan");
    // 序列化
    String json = mapper.writeValueAsString(user);

    // 反序列化，接收两个参数：json数据，反序列化的目标类字节码
    User result = mapper.readValue(json, User.class);
    System.out.println("result = " + result);
}

3. json转集合

   private ObjectMapper mapper = new ObjectMapper();
      
      @Test
      public void testJson() throws IOException {
          User user = new User();
          user.setId(8L);
          user.setAge(21);
          user.setName("柳岩");
          user.setUserName("liuyan");
      
          // 序列化,得到对象集合的json字符串
          String json = mapper.writeValueAsString(Arrays.asList(user, user));
      
          // 反序列化，接收两个参数：json数据，反序列化的目标类字节码
          List<User> users = mapper.readValue(json, mapper.getTypeFactory().constructCollectionType(List.class, User.class));
          for (User u : users) {
              System.out.println("u = " + u);
          }
      }

4. json转任意复杂类型

private ObjectMapper mapper = new ObjectMapper();

@Test
public void testJson() throws IOException {
    User user = new User();
    user.setId(8L);
    user.setAge(21);
    user.setName("柳岩");
    user.setUserName("liuyan");

    // 序列化,得到对象集合的json字符串
    String json = mapper.writeValueAsString(Arrays.asList(user, user));

    // 反序列化，接收两个参数：json数据，反序列化的目标类字节码
    List<User> users = mapper.readValue(json, new TypeReference<List<User>>(){});
    for (User u : users) {
        System.out.println("u = " + u);
    }
}

FastJSON

1. java对象转 json字符串

/**
    * java对象转 json字符串 
    */
   @Test
   public void objectTOJson(){
       //简单java类转json字符串
       User user = new User("dmego", "123456");
       String UserJson = JSON.toJSONString(user);
       System.out.println("简单java类转json字符串:"+UserJson);
       
       //List<Object>转json字符串
       User user1 = new User("zhangsan", "123123");
       User user2 = new User("lisi", "321321");
       List<User> users = new ArrayList<User>();
       users.add(user1);
       users.add(user2);
       String ListUserJson = JSON.toJSONString(users);
       System.out.println("List<Object>转json字符串:"+ListUserJson);   
       
       //复杂java类转json字符串
       UserGroup userGroup = new UserGroup("userGroup", users);
       String userGroupJson = JSON.toJSONString(userGroup);
       System.out.println("复杂java类转json字符串:"+userGroupJson);       
       
   }

2. json字符串转java对象

/**
    * json字符串转java对象
    * 注：字符串中使用双引号需要转义 (" --> \"),这里使用的是单引号
    */
   @Test
   public void JsonTOObject(){
       /* json字符串转简单java对象
        * 字符串：{"password":"123456","username":"dmego"}*/
       
       String jsonStr1 = "{'password':'123456','username':'dmego'}";
       User user = JSON.parseObject(jsonStr1, User.class);
       System.out.println("json字符串转简单java对象:"+user.toString());
       
       /*
        * json字符串转List<Object>对象
        * 字符串：[{"password":"123123","username":"zhangsan"},{"password":"321321","username":"lisi"}]
        */
       String jsonStr2 = "[{'password':'123123','username':'zhangsan'},{'password':'321321','username':'lisi'}]";
       List<User> users = JSON.parseArray(jsonStr2, User.class);
       System.out.println("json字符串转List<Object>对象:"+users.toString());
           
       /*json字符串转复杂java对象
        * 字符串：{"name":"userGroup","users":[{"password":"123123","username":"zhangsan"},{"password":"321321","username":"lisi"}]}
        * */
       String jsonStr3 = "{'name':'userGroup','users':[{'password':'123123','username':'zhangsan'},{'password':'321321','username':'lisi'}]}";
       UserGroup userGroup = JSON.parseObject(jsonStr3, UserGroup.class);
       System.out.println("json字符串转复杂java对象:"+userGroup);  
   }

GSON

todo

参考资料