AJAX..

Users

package bean;

public class Users {

    private Integer uid;
    private String username;
    private String password;
    private Double money;

    public Users() {
    }

    public Users(Integer uid, String username, String password, Double money) {
        this.uid = uid;
        this.username = username;
        this.password = password;
        this.money = money;
    }

    public Integer getUid() {
        return uid;
    }

    public void setUid(Integer uid) {
        this.uid = uid;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getpassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Double getMoney() {
        return money;
    }

    public void setMoney(Double money) {
        this.money = money;
    }

    @Override
    public String toString() {
        return "Users{" +
                "uid=" + uid +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", money=" + money +
                '}';
    }
}

GetUSeRSServlet

package servlet;

import bean.Users;
import net.sf.json.JSONObject;

import javax.servlet.servletexception;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(urlPatterns = "/getuser")
public class GetUSeRSServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws servletexception, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws servletexception, IOException {
        //1.接收参数
        String uid = req.getParameter("uid");
        int userid = Integer.parseInt(uid);
        Users users = null;
        switch (userid){
            case 1:
                users=new Users(1,"张三1","abc1",11.11);
                break;
            case 2:
                users=new Users(2,"张三2","abc2",11.22);
                break;
            case 3:
                users=new Users(3,"张三3","abc3",11.33);
                break;
            case 4:
                users=new Users(4,"张三4","abc4",11.44);
                break;
            default:
                users=new Users();
        }

        //java->json
        JSONObject jsonObject = JSONObject.fromObject(users);

        resp.setContentType("text/html;charset=utf-8");
        PrintWriter writer = resp.getWriter();
        writer.println(jsonObject);
    }
}

TestServlet

package servlet;

import javax.servlet.servletexception;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(urlPatterns = "/testuname")
public class TestServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws servletexception, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws servletexception, IOException {
        //1.接收参数
        String username = req.getParameter("username");
        resp.setContentType("text/html;charset=utf-8");
        PrintWriter writer = resp.getWriter();

        if("admin".equals(username)){
            writer.println("账户已被注册");
        }else {
            writer.println("账户可用");
        }
    }
}

Demo

package test;

import bean.Users;
import net.sf.json.JSON;
import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

import java.util.ArrayList;

public class Demo {
    public static void main(String[] args) {
        //java->json
        Users users = new Users(11,"aaa","123456",123.456);
        JSONObject jsonObject = JSONObject.fromObject(users);
        System.out.println(jsonObject);//json

        //json->java
        String str="{\"money\":123.456,\"password\":\"123456\",\"uid\":11,\"username\":\"aaa\"}";
        JSONObject jsonObject1 = JSONObject.fromObject(str);
        Object o = JSONObject.toBean(jsonObject1, Users.class);
        System.out.println("o="+o);

        //java集合->json
        ArrayList arrayList = new ArrayList();
        arrayList.add(new Users(1,"张三1","123",12.34));
        arrayList.add(new Users(2,"张三2","12322",1244.34));
        arrayList.add(new Users(3,"张三3","12333",1255.34));
        JSONArray jsonArray = JSONArray.fromObject(arrayList);//json
        System.out.println(jsonArray);

        //json->java集合
        String str2="[{\"money\":12.34,\"password\":\"123\",\"uid\":1,\"username\"" +
                ":\"张三1\"},{\"money\":1244.34,\"password\":\"12322\",\"uid\":2,\"username\"" +
                ":\"张三2\"},{\"money\":1255.34,\"password\":\"12333\",\"uid\":3,\"username\"" +
                ":\"张三3\"}]";
        JSONArray jsonArray1 = JSONArray.fromObject(str2);
        Object[] o1 = (Object[]) JSONArray.toArray(jsonArray1, Users.class);
        for(Object o2 : o1){
            System.out.println("o2="+o2);
        }
    }
}

index.jsp

<%--
  Created by IntelliJ IDEA.
  User: 28734
  Date: 2021/9/5
  Time: 9:58
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <script>
    function test(){
      //发送异步请求
      //1.创建XMLHttpRequest对象
      var xmlhttp;
      if(window.XMLHttpRequest){
        //非IE
        xmlhttp=new XMLHttpRequest();
      }else if(window.ActiveXObject){
        xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
      }
      //2.打开链接
      var uname=document.getElementById("uname").value;
      //xmlhttp.open("get","/testuname?username="+uname,true);
      xmlhttp.open("post","/testuname",true);
      //3.指定回调函数
      xmlhttp.onreadystatechange=function (){
        //3.1 判断状态
        if(xmlhttp.readyState==4){
          //3.2 接收返回的数据
          var responseText = xmlhttp.responseText;
          document.getElementById("rs").innerText=responseText;
        }
      }
      //4.发送数据
      //xmlhttp.send();

      //post
      xmlhttp.setRequestHeader("Content-type","application/x-www-form-urlencoded;charset=UTF-8");
      xmlhttp.send("username="+uname);
    }
  </script>
  <body>
  <h1>index.jsp</h1>

  username:<input type="text" id="uname" onblur="test()"><span id="rs"></span>
  </body>
</html>

jquery_ajax

<%--
  Created by IntelliJ IDEA.
  User: 28734
  Date: 2021/9/5
  Time: 9:58
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <script type="text/javascript" src="js/jquery-1.8.0.min.js"></script>
  <script type="text/javascript">
    $(function (){
      $("#uname").blur(function (){
        //1.获得value值
        var uname = $(this).val();
        //2.发送请求
        /*$.ajax({
          url:"/testuname",
          data:"username="+uname,
          type:"post",
          dataType:"text",
          success:function (rs){
            $("#rs").html(rs);
          }
        })*/

        /*$.get("/testuname","username="+uname,function (rs){
          $("#rs").html(rs);
        });
      });*/

        $.post("/testuname","username="+uname,function (rs){
          $("#rs").html(rs);
        });
      });
    })
  </script>
  <body>
  <h1>jquery_ajax.jsp</h1>

  username:<input type="text" id="uname"><span id="rs"></span>
  </body>
</html>

testjson.html

<!DOCTYPE html>
<html lang="en">
<head>
    <Meta charset="UTF-8">
    <title>Title</title>
  <script type="text/javascript">
    //1.定义json
    var j1={"name":"张三","age":18};
    //alert(j1.name+","+j1.age);
    //数组
    var j2={"names":["aa","bb","cc"]};
    //alert(j2.names[1]);
    //json数组内容
    var j3={"users":[{"name":"张三1","age":18},{"name":"张三2","age":14},{"name":"张三3","age":16}]}
    alert(j3.users[2].name);
  </script>
</head>
<body>

</body>
</html>

testjsondemo.jsp

<%--
  Created by IntelliJ IDEA.
  User: 28734
  Date: 2021/9/5
  Time: 12:26
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<script type="text/javascript" src="js/jquery-1.8.0.min.js"></script>
<script type="text/javascript">
  $(function (){
    $("#uid").blur(function (){
      //1.获得value值
      var uid = $(this).val();
      //2.发送请求
      $.post("/getuser","uid="+uid,function (rs){
          //转换成可以处理的js
          rs=eval("("+rs+")");
          //此时的rs是json格式的对象
          $("#name").val(rs.username);
          $("#pass").val(rs.password);
          $("#money").val(rs.money);
      });
    });
  })
</script>
<body>
  uid:<input type="text" id="uid"><br>
  name:<input type="text" id="name"><br>
  pass:<input type="text" id="pass"><br>
  money:<input type="text" id="money"><br>
</body>
</html>