JavaWeb实现登录验证码

在登录界面中使用图片验证码, 对于现在的web应用到处可见.

话不多说, 开始写代码了!
首先, 新建一个JSP, 表示登录界面:
login3.jsp文件:

<%--
  User: menglanyingfei
  Date: 2018/1/12
  Time: 16:16
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>



    


<%

    // 获取浏览器发送过来的cookie, 获取用户信息
    Cookie[] cookies = request.getCookies();
    String username = "";
    if (cookies != null) {
        for (Cookie cookie : cookies) {
            if ("username".equals(cookie.getName())) {
                username = cookie.getValue();
            }
        }
    }
%>
${requestScope.message}

    用户名:${requestScope.error}
    

    密码:
    

    验证码:
    
    ${requestScope.imageMess}
    

    

界面就是这样, 当然, 你肯定现在出来不了这个效果! 没事, 接着往下看吧!

登录界面.png

然后, 新建一个Servlet:
VerifyCodeServlet.java文件, 因为这里配置了@WebServlet注解, 所以无需在web.xml中配置!

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.image.BufferedImage;
import java.io.IOException;

/**
 * 用来生成图片验证码
 * Created by menglanyingfei on 2018/1/12.
 */
@WebServlet(name = "VerifyCodeServlet", value = "/VerifyCodeServlet")
public class VerifyCodeServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //创建对象
        VerifyCode vc = new VerifyCode();
        //获取图片对象
        BufferedImage bi = vc.getImage();
        //获得图片的文本内容
        String text = vc.getText();
        // 将系统生成的文本内容保存到session中
        request.getSession().setAttribute("text", text);
        //向浏览器输出图片
        vc.output(bi, response.getOutputStream());

    }
}

在同一包下, 新建一个Java文件VerifyCode.java(具体的代码意思, 可以看注释, 已经写得非常清楚了!):

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;

import javax.imageio.ImageIO;

public class VerifyCode {
    private int w = 70;
    private int h = 35;
    private Random r = new Random();
    // {"宋体", "华文楷体", "黑体", "华文新魏", "华文隶书", "微软雅黑", "楷体_GB2312"}
    private String[] fontNames  = {"宋体", "华文楷体", "黑体", "微软雅黑", "楷体_GB2312"};
    // 可选字符
    private String codes  = "0123456789abcdefghjkmnopqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ";
    // 背景色
    private Color bgColor  = new Color(255, 255, 255);
    // 验证码上的文本
    private String text ;
    
    // 生成随机的颜色
    private Color randomColor () {
        int red = r.nextInt(150);
        int green = r.nextInt(150);
        int blue = r.nextInt(150);
        return new Color(red, green, blue);
    }
    
    // 生成随机的字体
    private Font randomFont () {
        int index = r.nextInt(fontNames.length);
        String fontName = fontNames[index];//生成随机的字体名称
        int style = r.nextInt(4);//生成随机的样式, 0(无样式), 1(粗体), 2(斜体), 3(粗体+斜体)
        int size = r.nextInt(5) + 24; //生成随机字号, 24 ~ 28
        return new Font(fontName, style, size);
    }
    
    // 画干扰线
    private void drawLine (BufferedImage image) {
        int num  = 3;//一共画3条
        Graphics2D g2 = (Graphics2D)image.getGraphics();
        for(int i = 0; i < num; i++) {//生成两个点的坐标，即4个值
            int x1 = r.nextInt(w);
            int y1 = r.nextInt(h);
            int x2 = r.nextInt(w);
            int y2 = r.nextInt(h); 
            g2.setStroke(new BasicStroke(1.5F)); 
            g2.setColor(Color.BLUE); //干扰线是蓝色
            g2.drawLine(x1, y1, x2, y2);//画线
        }
    }
    
    // 随机生成一个字符
    private char randomChar () {
        int index = r.nextInt(codes.length());
        return codes.charAt(index);
    }
    
    // 创建BufferedImage
    private BufferedImage createImage () {
        BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB); 
        Graphics2D g2 = (Graphics2D)image.getGraphics(); 
        g2.setColor(this.bgColor);
        g2.fillRect(0, 0, w, h);
        return image;
    }
    
    // 调用这个方法得到验证码
    public BufferedImage getImage () {
        BufferedImage image = createImage();//创建图片缓冲区 
        Graphics2D g2 = (Graphics2D)image.getGraphics();//得到绘制环境
        StringBuilder sb = new StringBuilder();//用来装载生成的验证码文本
        // 向图片中画4个字符
        for(int i = 0; i < 4; i++)  {//循环四次，每次生成一个字符
            String s = randomChar() + "";//随机生成一个字母 
            sb.append(s); //把字母添加到sb中
            float x = i * 1.0F * w / 4; //设置当前字符的x轴坐标
            g2.setFont(randomFont()); //设置随机字体
            g2.setColor(randomColor()); //设置随机颜色
            g2.drawString(s, x, h-5); //画图
        }
        this.text = sb.toString(); //把生成的字符串赋给了this.text
        drawLine(image); //添加干扰线
        return image;       
    }
    
    // 返回验证码图片上的文本
    public String getText () {
        return text;
    }
    
    // 保存图片到指定的输出流
    public static void output (BufferedImage image, OutputStream out) 
                throws IOException {
        ImageIO.write(image, "JPEG", out);
    }
}

处理登录逻辑的Servlet(LoginServlet3.java):

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

/**
 * Created by menglanyingfei on 2018/1/12.
 */
@WebServlet(name = "LoginServlet3", value = "/LoginServlet3")
public class LoginServlet3 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 编码
        request.setCharacterEncoding("utf-8");
        // 获取请求参数
        /*
            拿到页面传过来的手动输入的验证码, 该验证码要和生成图片上的
            文本验证码比较, 如果相同, 验证码输入成功!
         */
        String imageText = request.getParameter("image");
        // 图片的验证码
        String text = (String) request.getSession().getAttribute("text");

        if (!text.equalsIgnoreCase(imageText)) {
            request.setAttribute("imageMess", "验证码输入错误!");
            request.getRequestDispatcher("/jsp/login3.jsp").forward(request, response);
        }
        // 获取用户名和密码
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        if ("haha".equals(username) && "123".equals(password)) {
            // 将用户信息保存到session中
            request.getSession().setAttribute("username", username);

            // 使用cookie实现回写用户名
            Cookie cookie = new Cookie("username", username);
            cookie.setMaxAge(60 * 60);
            // 通过响应头发送cookie
            response.addCookie(cookie);
            // 重定向登录成功界面
            response.sendRedirect(request.getContextPath() + "/jsp/success2.jsp");
        } else {
            request.setAttribute("error", "用户名或密码错误!");
            request.getRequestDispatcher("/jsp/login3.jsp").forward(request, response);
        }
    }

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

登录成功后的界面:(success2.jsp)

<%--
  User: menglanyingfei
  Date: 2018/1/12
  Time: 16:44
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>



    


<%
    // 获取用户信息
    String username = (String) session.getAttribute("username");

    if (username == null) {
        // 保存错误信息到request中, 然后转发到login3.jsp中, 提醒登录
        request.setAttribute("message", "请登录!");

        // 转发到登录页面
        request.getRequestDispatcher("/jsp/login3.jsp").forward(request, response);
    }
%>
欢迎登录:${sessionScope.username}!!!

最后, 演示登录:
因为, 用户名haha和密码123已经写死在代码里了!

登录.png

成功.png

完整代码地址

https://github.com/menglanyingfei/Java/tree/master/JavaWebTrain/day_1_12