How to return json in java

This article will introduce how to write a Java program to return Json data. This time, it will be introduced in three ways.

Recommended course: Java tutorial

Java method to return json:

Method 1: Of course, type all the code by hand to return json data.

Requires HttpHttpServletRequest request HttpServletResponse response

Backend:

@RequestMapping(value="/haha")
 
public void xxx (HttpHttpServletRequest request，HttpServletResponse response)
{     JSONObject json =new JSONObject();
      json.put("result"," success")
      response.setCharacterEncoding("utf-8");
response.setContentType("application/json;charset=utf-8");
      PrintWriter out = null;
      out = response.getWriter();
      out.write(json.toString()); 
}

Front-end:

$.ajax({
data : {
// userNameOrTel: $("#user").val(),
// password: $("#pwd").val()
},
type : "post",  
url : "admin/login/",
dataType : "json",
contentType : "application/json;charset=utf-8", 
async : false,  //同步 异步
success : function(data) {
    debugger; 
}
}
});

Method 2: @ResponseBody Annotation

Backend:

@ResponseBody 
@RequestMapping(value="/haha")
public Msg xxx (){  return msg }

Front-end:

$.ajax({
data : {
// userNameOrTel: $("#user").val(),
// password: $("#pwd").val()
},
type : "post",  
url : "admin/login/",
dataType : "json",
contentType : "application/json;charset=utf-8", 
async : false,  //同步 异步
success : function(data) {
    debugger; 
}
}
});

Method 3: @RestController annotation (in this class So the method return values ​​are all Json)

Front end:

data:JSON.stringify({'channelId':channelId}),
                  success:function(data){
                        alert(data.channelId);
                  },
 
contentType:'application/json;charset=utf-8'

Backend:

@RequestMapping(value="/login",produces="application/json;charset=UTF-8") @ResponseBody public String test2() {  }

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