1.打开IDEA,新建login.jsp文件
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>登录</title>
</head>
</form>
<form method="post" action="LoginServlet">
账号：<input type="text" name="username" size="20" maxlength="20" id="user"/><br>
密码：<input type="password" name="pwd" size="20" maxlength="20" id="psd"/><br>
<button onclick="validateLogin()">提交</button>
<input type="reset" value="重置" />
</form>
<script>
function validateLogin(){
var sUserName = document.getElementById("user").value;
var sPassword = document.getElementById("psd").value;
if (sUserName==""){
alert("请输入用户名!");
}
if (sPassword==""){
alert("请输入密码!");
}
}
</script>
</body>
</html>
2.打开MySQL数据库图形化管理软件，创建数据库
letterwish为数据库，users为表名
3.在web-inf下创建lib文件夹，将MySQL驱动加载包复制到此文件夹
4.打开IDEA，在src文件夹下创建servlet包，在包下创建LoginServlet.java类
package servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.sql.*;
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public LoginServlet() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.getWriter().append("Served at: ").append(request.getContextPath());
}
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
request.setCharacterEncoding("utf-8");
String username = request.getParameter("username");
String pwd = request.getParameter("pwd");
try {
Class.forName("com.mysql.cj.jdbc.Driver");
} catch (ClassNotFoundException e) {
e.printStackTrace();
System.out.println("找不到驱动 ");
}
// 连接URL 服务器地址 端口号 数据库名
String url = "jdbc:mysql://localhost:3306/letterwish";
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try { //数据库的登录名 登录密码
conn =DriverManager.getConnection(url, "root", "2001223");
stmt =conn.createStatement();
// SQL语句
String sql = "select * from users where account='" + username + "' and pwd= '" + pwd + "'";
rs = stmt.executeQuery(sql);// 返回查询结果
} catch (SQLException e) {
e.printStackTrace();
}
HttpSession session = request.getSession();
session.setAttribute("username", username);
try {
if (rs.next()) {
// 如果记录集非空，表明有匹配的用户名和密码，登陆成功
response.sendRedirect("index.jsp");
} else {
session.setAttribute("message", "用户名或密码不匹配。");
response.getWriter().write("用户名或密码不匹配");
}
rs.close();
stmt.close();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
5.配置文件，找到web-inf文件下的web.xml文件中添加如下代码
<servlet>
<servlet-name>a</servlet-name>
<servlet-class>servlet.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>a</servlet-name>
<url-pattern>/LoginServlet</url-pattern>
</servlet-mapping>