Servlet+JDBC实现登陆功能的小例子(带验证码)

Servlet+JDBC实现登陆功能的小例子(带验证码)

案例需求：访问带有验证码的登录页面login.jsp用户输入用户名，密码以及验证码。如果用户名和密码输入有误，跳转登录页面，提示:用户名或密码错误如果验证码输入有误，跳转登录页面，提示：验证码错误如果全部输入正确，则跳转到主页success.jsp，显示：用户名,欢迎您分析

步骤

文件树展示

1.配置文件和jar包在上个案例均有配置过，需要改的有：User类新增验证码成员变量，数据库增加了一个验证码字段（无用，只是为了UserDao包把查找到的数据值导入到User类不出错）。

2.登陆界面

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

3.验证码，画了个验证码，每次都把随机数加入session中以便进行对比

package Test;

import javax.imageio.ImageIO;

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.awt.*;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.util.Random;

@WebServlet("/checkCodepic")

public class CheckCodepic extends HttpServlet {

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

int width=100;

int height=50;

//创建图片对象

BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);

//美化图片

//创建画笔

Graphics g = image.getGraphics();

//画笔颜色

g.setColor(Color.pink);

//画个矩形，填充为粉红色

g.fillRect(0,0,width,height);

//给矩形加边框

g.setColor(Color.blue);

g.drawRect(0,0,width-1,height-1);

//写字母或数字

g.setColor(Color.green);

String str="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

Random rd=new Random();

StringBuilder sb=new StringBuilder();

for(int i=1;i<=4;i++){

int index = rd.nextInt(str.length());

char c = str.charAt(index);

sb.append(c);

g.drawString(c+"",width/5*i,height/2);

}

String checkCode_session = sb.toString();

//将验证码存入session

req.getSession().setAttribute("checkCode_session",checkCode_session);

//加干扰线

g.setColor(Color.blue);

for(int i=1;i<=10;i++){

int x1 = rd.nextInt(width);

int x2 = rd.nextInt(width);

int y1 = rd.nextInt(height);

int y2 = rd.nextInt(height);

g.drawLine(x1,y1,x2,y2);

}

//输出展示

ImageIO.write(image,"jpg",resp.getOutputStream());

}

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

this.doPost(req,resp);

}

}

4.loginServlet类，用来判断验证码和用户名密码是否正确，注意先判断验证码；注意重定向和请求转发的不同，还有session的应用。

package Test;

import Test.dao.UserDao;

import Test.userclass.User;

import org.apache.commons.beanutils.BeanUtils;

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.lang.reflect.InvocationTargetException;

import java.util.Map;

@WebServlet("/loginServlet")

public class loginServlet extends HttpServlet {

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

//设置request编码

request.setCharacterEncoding("utf-8");

//获取参数

// String username = request.getParameter("username");

// String password = request.getParameter("password");

// String checkCode = request.getParameter("checkCode");

// User user=new User();

// user.setUsername(username);

// user.setPassword(password);

// user.setCheckCode(checkCode);

Map parameterMap = request.getParameterMap();

User user=new User();

try {

BeanUtils.populate(user,parameterMap);

} catch (IllegalAccessException e) {

e.printStackTrace();

http:// } catch (InvocationTargetException e) {

e.printStackTrace();

}

UserDao userDao=new UserDao();

//先判断验证码是否正确

String checkCode_session = (String)request.getSession().getAttribute("checkCode_session");

request.getSession().removeAttribute("checkCode_session");

if(checkCode_session!=null && checkCode_session.equalsIgnoreCase(user.getCheckCode())){//忽略大小写

//如果正确，判断用户名密码是否正确

User login = userDao.login(user);

if(login!=null){

//登陆成功，存储用户信息

request.getSession().setAttribute("username",login.getUsername());

//重定向到success.jsp

response.sendRedirect(request.getContextPath()+"/success.jsp");

}else{//登陆失败，转发到登陆界面

request.setAttribute("login_error","用户名或密码不正确");

request.getRequestDispatcher("/login.jsp").forward(request,response);

}

}else{ //如果不正确，转发到登陆界面

request.setAttribute("cc_error","验证码不正确");

request.getloTFoRequestDispatcher("/login.jsp").forward(request,response);

}

}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

this.doPost(request, response);

}

}

5.成功登陆界面

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

结果

登陆界面

验证码错误情况

用户名或密码不正确情况

成功登陆

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