关于把AJAX加入到注册登录demo中去

package com.ykmimi.login;
 
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;
 
WebServlet(name = "CheckNameServlet")
public class CheckNameServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 
//设置请求编码
request.setCharacterEncoding("UTF-8");
//获取请求数据
String loginName = request.getParameter("loginName");
//简单判定
if ("admin".equals(loginName)) {
request.setAttribute("data",false);
request.getRequestDispatcher("data.jsp").forward(request,response);
return;
}
request.setAttribute("data", true);
request.getRequestDispatcher("data.jsp").forward(request, response);
 
 
}
 
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
super.doPost(request, response);
 
 
}
}

package com.ykmimi.login;
 
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;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
 
public class CheckNameServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
 
// 设置请求编码
request.setCharacterEncoding("UTF-8");
// 获取请求数据
String userName = request.getParameter("userName");
 
//
String driverName = "org.mariadb.jdbc.Driver";
String DBUrl = "jdbc:mariadb://**.**.**.**:3306/*****";
String DBUser = "******";
String DBPassword = "************";
PrintWriter pw = response.getWriter();
 
try {
Class.forName(driverName);
Connection conn = DriverManager.getConnection(DBUrl, DBUser, DBPassword);
 
String sql = "SELECT * FROM user WHERE username = '" + userName + "'";
Statement stmt1 = conn.createStatement();
ResultSet name = stmt1.executeQuery(sql);
 
if (name.next()) {
request.setAttribute("data", false);
request.getRequestDispatcher("data.jsp").forward(request, response);
return;
}
request.setAttribute("data", true);
request.getRequestDispatcher("data.jsp").forward(request, response);
 
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
 
 
}
 
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
super.doPost(request, response);
 
}
}