JSP与Servlet组合实现登录功能（附加验证码）

天道Vax的时间宝藏

发布于 2021-08-11 10:47:05

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发布于 2021-08-11 10:47:05

User.java

package com.bean;

public class xzk_User {
	String userid;
	String password;
	public String getUserid() {
		return userid;
	}
	public String getPassword() {
		return password;
	}
	public void setUseid(String id) {
		userid=id;
	}
	public void setPassword(String pw) {
		password=pw;
	}
}

index.jsp

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>首页</title>
</head>
<body>
	<jsp:forward page="login.jsp"></jsp:forward>
</body>
</html>

login.jsp

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>登录</title>
<style type="text/css"> div{text-align:center}</style>
</head>
<body>
<div>
	<form name="reg" action="/2019_11_14_xzk.test/XZK_LoginServlet" method="post">
		用户名：<input name="userid" type="text" size="30"/><br />
		密   码 ：<input name="password" type="password" size="30"/><br />
		验证码：<input type="text" name="check_code" size="20">
			  <img src="XZK_CheckServlet"><br />
		<input type="submit" value="提交" id="bt" />
	</form>
</div>
<!-- JSP页面的普通注释:注释的内容是可见的，将出现在生成的HTML代码中，此代码将发送给
浏览器，然后由浏览器负责忽略此注释。 -->
<%-- JSP页面中的隐藏注释:标记的内容客户端查看源码时是完全看不到的。 --%>
<% // JSP中java代码块单行注释：客户端不可见 %> 
<% /* JSP中java代码块多行注释：客户端不可见 */ %>
</body>
</html>

LoginServlet.java

package com.loginPage;

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;
import com.bean.xzk_User;

public class XZK_LoginServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
	public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		resp.setContentType("text/html;charset=utf-8");
		String userid=req.getParameter("userid");
		String password=req.getParameter("password");
		String checkCode=req.getParameter("check_code");
		String savedCode=(String )req.getSession().getAttribute("check_code");
		PrintWriter pw=resp.getWriter();
		if(("xzk").equals(userid)&&("521").equals(password)&&checkCode.equals(savedCode)) {//少验证码验证部分
			xzk_User user=new xzk_User();
			user.setUseid(userid);
			user.setPassword(password);
			req.getSession().setAttribute("user", user);
			resp.sendRedirect("/2019_11_14_xzk.test/main.jsp");
		}else if(checkCode.equals(savedCode)){
			pw.write("用户名或密码错误，登陆失败，请您重新输入");
		}else {
			pw.write("验证码错误");
		}
		
		//response.getWriter().append("Served at: ").append(request.getContextPath());
	}

	public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(req, resp);
	}

}

main.jsp

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8" import="com.bean.*"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>首页</title>
<style>
    *{
    padding:0;
    margin:0;
    font-family:"微软雅黑";
}
.header{
    height:72px;
    background:#458fce ;
}
.header .logo{
    color:#fff ;
    line-height:70px;
    font-size:30px;
    margin-left:20px;
    display:inline-block;
    text-align:center;

}
a {
    color: #fff ;
    text-decoration: none ;
}
.header .login{
    float:right;
    color:#fff ;
    line-height:72px;
    margin-right:2px;
    display:inline-block;
}
.banner{
    height:380px;
    overflow:hidden;
    background: #ddd;
}
</style>
</head>
<body>
    <div class="header">
        <div class="logo">JavaWeb实验一</div>
        <div class ="login">
            <a href ="/2019_11_14_xzk.test/XZK_IndexServlet">个人中心</a>
            <span>|</span> 
            <a href ="/2019_11_14_xzk.test/XZK_LoginOutServlet">退出</a>
        </div>
    </div>
    <br />
    	用户名：xzk
    <% 
    	xzk_User u=(xzk_User)new xzk_User();
    %>
    <!-- JSP页面的普通注释:注释的内容是可见的，将出现在生成的HTML代码中，此代码将发送给浏览器，然后由浏览器负责忽略此注释。 -->
	<%-- JSP页面中的隐藏注释:标记的内容客户端查看源码时是完全看不到的。 --%>

	<% // JSP中java代码块单行注释：客户端不可见 %> 
	<% /* JSP中java代码块多行注释：客户端不可见 */ %>
</body>
</html>

IndexServlet.java

package com.loginPage;

import java.io.IOException;
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 com.bean.xzk_User;

public class XZK_IndexServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
		HttpSession session = request.getSession();
		xzk_User user = (xzk_User) session.getAttribute("user");
		if(user == null){
			response.getWriter().print("你还没有登陆或输入用户名,请重新登录<a href='/2019_11_14_xzk.test/main.jsp'>进入首页</a>");
		} else {
			response.getWriter().print("你已经登陆成功欢迎你" + user.getUserid() + "!");
			response.getWriter().print("<a href='/2019_11_14_xzk.test/XZK_LoginOutServlet'>退出</a>");
			}
	}
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}
}

LoginoutServlet.java

package com.loginPage;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class XZK_LoginOutServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		req.getSession().removeAttribute("userid");
		resp.sendRedirect("/2019_11_14_xzk.test/index.jsp");
		//response.getWriter().append("Served at: ").append(request.getContextPath());
	}

	public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {	
		doGet(req, resp);
	}
}

CheckServlet.java

package com.loginPage;
 import java.io.*;
 import javax.servlet.*;
 import javax.servlet.http.*;
 import java.awt.*;
 import java.awt.image.*;
 import javax.imageio.ImageIO;
 public class XZK_CheckServlet extends HttpServlet
 {
	private static final long serialVersionUID = 1L;
	private static int WIDTH = 60; //验证码图片宽度
 	private static int HEIGHT = 20; //验证码图片高度
 public void doGet(HttpServletRequest request,HttpServletResponse response) 
 			throws ServletException,IOException{		
 		HttpSession session = request.getSession();
 		response.setContentType("image/jpeg");
 		ServletOutputStream sos = response.getOutputStream();		    response.setHeader("Pragma","No-cache");
 		response.setHeader("Cache-Control","no-cache");
 		response.setDateHeader("Expires", 0);
		BufferedImage image = 
 			new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB); 
 		Graphics g = image.getGraphics();
 		char [] rands = generateCheckCode();
 		drawBackground(g);
 		drawRands(g,rands);
		g.dispose();
		ByteArrayOutputStream bos = new ByteArrayOutputStream();
 		ImageIO.write(image, "JPEG", bos);
 		byte [] buf = bos.toByteArray();
 		response.setContentLength(buf.length);
		sos.write(buf);
 		bos.close();
 		sos.close();
 		session.setAttribute("check_code",new String(rands));
	}
	private char [] generateCheckCode()
 	{
 		String chars = "0123456789abcdefghijklmnopqrstuvwxyz";
 		char [] rands = new char[4];
 		for(int i=0; i<4; i++)
 		{
 			int rand = (int)(Math.random() * 36);
 			rands[i] = chars.charAt(rand);
 		}
 		return rands;
 	}
 	private void drawRands(Graphics g , char [] rands)
 	{
 		g.setColor(Color.BLACK);
 		g.setFont(new Font(null,Font.ITALIC|Font.BOLD,18));
 		g.drawString("" + rands[0],1,17);
 		g.drawString("" + rands[1],16,15);
 		g.drawString("" + rands[2],31,18);
 		g.drawString("" + rands[3],46,16);
 		System.out.println(rands);
 	}
 	private void drawBackground(Graphics g)
 	{
 		g.setColor(new Color(0xDCDCDC));
 		g.fillRect(0, 0, WIDTH, HEIGHT);
		for(int i=0; i<120; i++)
 		{
 			int x = (int)(Math.random() * WIDTH);
 			int y = (int)(Math.random() * HEIGHT);
 			int red = (int)(Math.random() * 255);
 			int green = (int)(Math.random() * 255);
 			int blue = (int)(Math.random() * 255);
 			g.setColor(new Color(red,green,blue));		
 			g.drawOval(x,y,1,0);
 		}
 	}
 }

总结：刚一开始不明白JSP与html文件的具体区别，在理解上出了问题，后来通过查阅，明白JSP相对于html是会产生动态页面，且JSP只有发布到Tomcat服务器上才能打开，而html是直接可以打开的。另外能熟练掌握区分JSP中三种注释：JSP普通注释，JSP隐藏注释还有java代码注释。熟练掌握JSP语言的page属性值以及标识性动作forward的用法。

本文参与腾讯云自媒体同步曝光计划，分享自作者个人站点/博客。

原始发表：2019/11/17 ，如有侵权请联系 cloudcommunity@tencent.com 删除

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