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Ajax front-end and back-end interaction implementation methods using JSON

小云云Original: 2018-01-22 13:16:422605browse

This article mainly introduces examples of jQuery Ajax front-end and back-end interaction using JSON. The front-end transmits json to the back-end through jQuery Ajax. The back-end receives json, processes the json, and the back-end returns a json to the front-end. If you are interested, you can Find out more, hope it helps everyone.

Requirements:

The front end transmits json to the back end through jQuery Ajax, the back end receives json, processes the json, and the back end returns a json to the front end

How to use servlet here

1. Use $.post method

index.jsp page

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<%@ page contentType="text/html; charset=UTF-8"%> 
<html> 
<head> 
<title></title> 
<script src="js/jquery-1.12.2.js"></script> 
<script language="JavaScript"> 
  function checkUserid() { 
    $.post(&#39;Ajax/CheckServlet&#39;,//url 
    { 
      userid : $("#userid").val(), 
      sex : "男" 
    }, function(data) { 
      var obj = eval(&#39;(&#39; + data + &#39;)&#39;); 
      alert(obj.success); 
    }); 
  } 
</script> 
</head> 
<body> 
  用户ID: 
  <input type="text" id="userid" name="userid"> <span id="msg"></span> 
  <br> <button onclick="checkUserid()">传输</button> 
</body> 
</html>

CheckServlet.Java code is as follows

package com.ajax; 
 
import java.io.IOException; 
import java.io.PrintWriter; 
 
import javax.servlet.ServletException; 
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
 
public class CheckServlet extends HttpServlet { 
 
  public void doGet(HttpServletRequest request, HttpServletResponse response) 
      throws ServletException, IOException { 
    this.doPost(request, response); 
  } 
 
  public void doPost(HttpServletRequest request, HttpServletResponse response) 
      throws ServletException, IOException { 
    /*设置字符集为&#39;UTF-8&#39;*/ 
    request.setCharacterEncoding("UTF-8"); 
    response.setCharacterEncoding("UTF-8"); 
    String userid = request.getParameter("userid"); // 接收userid 
    String sex = request.getParameter("sex");//接收性别 
    System.out.println(userid); 
    System.out.println(sex); 
 
    //写返回的JSON 
    PrintWriter pw = response.getWriter(); 
    String json = "{&#39;success&#39;:&#39;成功&#39;,&#39;false&#39;:&#39;失败&#39;}"; 
    pw.print(json); 
    pw.flush(); 
    pw.close(); 
 
  } 
}

Since the servlet method is used here, web.xml must be configured

<?xml version="1.0" encoding="UTF-8"?> 
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xmlns="http://xmlns.jcp.org/xml/ns/javaee" 
  xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" 
  id="WebApp_ID" version="3.1"> 
  <display-name>Ajax</display-name> 
 
  <servlet> 
    <servlet-name>CheckServlet</servlet-name> 
    <servlet-class>com.ajax.CheckServlet</servlet-class> 
  </servlet> 
  <servlet-mapping> 
    <servlet-name>CheckServlet</servlet-name> 
    <url-pattern>/Ajax/CheckServlet</url-pattern> 
  </servlet-mapping> 
</web-app>

Enter an ID on the page, which can be received and printed in the background. The background uses PrintWriter to write back JSON and returns it to the front end. The front end uses eval to convert JSON into an Object object, and obtains the JSON value through obj.name

2. Using the $.get method, you only need to change the post in the jsp page to get

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<%@ page contentType="text/html; charset=UTF-8"%> 
<html> 
<head> 
<title></title> 
<script src="js/jquery-1.12.2.js"></script> 
<script language="JavaScript"> 
  function checkUserid() { 
    $.get( 
      &#39;Ajax/CheckServlet&#39;,//url 
      { 
        userid:$("#userid").val(), 
        sex:"男" 
      }, 
      function(data){ 
        var obj = eval(&#39;(&#39;+data+&#39;)&#39;); 
        alert(obj.success); 
      } 
    ); 
  } 
</script> 
</head> 
<body> 
 
  用户ID: 
  <input type="text" id="userid" name="userid"> <span id="msg"></span> 
    <br> 
      <button onclick="checkUserid()">传输</button> 
</body> 
</html>

The result is the same as $.post

3. Through the $.ajax method

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<%@ page contentType="text/html; charset=UTF-8"%> 
<html> 
<head> 
<title></title> 
<script src="js/jquery-1.12.2.js"></script> 
<script language="JavaScript"> 
  function checkUserid() { 
    $.ajax({ 
      type : &#39;post&#39;, 
      data : { 
        userid : $("#userid").val(), 
        sex : "男" 
      }, 
      url : "Ajax/CheckServlet", 
      success : function(data) { 
        var obj = eval(&#39;(&#39; + data + &#39;)&#39;); 
      alert(obj.success); 
      }, 
      error : function() { 
      }, 
      complete : function() { 
      } 
    }); 
  } 
</script> 
</head> 
<body> 
 
  用户ID: 
  <input type="text" id="userid" name="userid"> <span id="msg"></span> 
    <br> 
      <button onclick="checkUserid()">传输</button> 
</body> 
</html>

$.ajax method can also be divided into post and get methods. Modify the sending method by modifying the type

The result is the same as method 1

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Two methods for javascript to parse url into json format

Completely master the principles and implementation methods of jsonp

JS obtains multiple pieces of data in a form field and converts them into json format Example sharing

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