02javaweb基础：Jsp+Servlet实现的数字验证码

1：功能说明：验证码登陆验证

2：功能展示：

3：代码：

3.1：LoginServlet.java    //登陆主要的逻辑功能

package com.sample.servlet;
/**
 * 
Title: LoginServlet
 * 
Description: 用来验证验证码是否正确，结果会向控制台打印并跳转页面successful.jsp|erro.jsp
 * @author Mr_z
 * @time 2018年3月2日
 *       下午4:39:35
 */
import java.io.IOException;
import java.util.Date;
import javax.servlet.RequestDispatcher;
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 javax.swing.JOptionPane;
public class LoginServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
	@Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		JOptionPane.showMessageDialog(null, "标题【出错啦】", "年龄请输入数字", JOptionPane.ERROR_MESSAGE);
    	String validationCode = req.getParameter("validationCode");
        HttpSession session = req.getSession();
        String validation_code = (String)session.getAttribute("validation_code");
        System.out.print(new Date(System.currentTimeMillis()));
    	System.out.println("--from class LoginServlet -> Accepted validation code:"+validation_code.toString());
        if(validationCode.equalsIgnoreCase(validation_code)){
        	System.out.print(new Date(System.currentTimeMillis()));
        	System.out.println("--from class LoginServlet -> Correct verification code");
            RequestDispatcher rd = req.getRequestDispatcher("successful.jsp");
            rd.forward(req, resp);
        }else{
        	System.out.print(new Date(System.currentTimeMillis()));
        	System.out.println("--from class LoginServlet -> False verification code");
            RequestDispatcher rd = req.getRequestDispatcher("erro.jsp");
            rd.forward(req, resp);
        }
        
    }
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         doGet(request,response);
    }

}

3.2：ValidateCode.java       //生成验证码图片

package com.sample.servlet;
/**
 * 
Title: ValidateCode
 * 
Description:用来生成验证码，生成一次验证码会向控制台打印一次 
 * @author Mr_z
 * @time 2018年3月2日
 *       下午4:38:27
 */
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Date;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class ValidateCode extends HttpServlet {
	private static final long serialVersionUID = 1L;
	private static String codeChars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        // 获得验证码集合的长度
        int charsLength = codeChars.length();
        // 下面3条记录是关闭客户端浏览器的缓冲区
        // 这3条语句都可以关闭浏览器的缓冲区，但是由于浏览器的版本不同，对这3条语句的支持也不同
        // 因此，为了保险起见，同时使用这3条语句来关闭浏览器的缓冲区
        response.setHeader("ragma", "No-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        // 设置图形验证码的长和宽
        int width = 90, height = 30;
        BufferedImage image = new BufferedImage(width, height,
                BufferedImage.TYPE_INT_RGB);
        Graphics g = image.getGraphics();
        Random random = new Random();
        g.setColor(getRandomColor(180, 250));
        g.fillRect(0, 0, width, height);
        g.setFont(new Font("Times New Roman", Font.ITALIC, height));
        g.setColor(getRandomColor(120, 180));
        // 用户保存最后随机生成的验证码
        StringBuffer validationCode = new StringBuffer();
        // 验证码的随机字体
        String[] fontNames = { "Times New Roman", "Book antiqua", "Arial" };
        // 随机生成4个验证码
        for (int i = 0; i < 4; i++) {
            // 随机设置当前验证码的字符的字体
            g.setFont(new Font(fontNames[random.nextInt(3)], Font.ITALIC,
                    height));
            // 随机获得当前验证码的字符
            char codeChar = codeChars.charAt(random.nextInt(charsLength));
            validationCode.append(codeChar);
            // 随机设置当前验证码字符的颜色
            g.setColor(getRandomColor(10, 100));
            // 在图形上输出验证码字符，x和y都是随机生成的
            g.drawString(String.valueOf(codeChar), 16 * i + random.nextInt(7),
                    height - random.nextInt(6));
        }
        // 获得HttpSession对象
        HttpSession session = request.getSession();
        // 设置session对象5分钟失效
        session.setMaxInactiveInterval(5 * 60);
        // 将验证码保存在session对象中,key为validation_code
        session.setAttribute("validation_code", validationCode.toString());
        System.out.print(new Date(System.currentTimeMillis()));
        System.out.println("--from class ValidateCode -> Generate a verifying code:"+validationCode.toString());
         //关闭Graphics对象
        g.dispose();
        OutputStream outS = response.getOutputStream();
        ImageIO.write(image, "JPEG", outS);
    }
    private Color getRandomColor(int minColor, int maxColor) {
          Random random = new Random();
            if(minColor > 255){
                minColor = 255;
            }
            if(maxColor > 255){
                maxColor = 255;
            }
            //获得r的随机颜色值
            int red = minColor+random.nextInt(maxColor-minColor);
            int green = minColor + random.nextInt(maxColor-minColor);
            int blue = minColor + random.nextInt(maxColor-minColor);
            return new Color(red,green,blue);
    }

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

}

3.3：web.xml

  yzm
  
    login.jsp
  
  
    loginServlet
    com.sample.servlet.LoginServlet
  
  
    loginServlet
    /loginServlet
  
  
    validateCode
    com.sample.servlet.ValidateCode
  
  
    validateCode
    /validateCode
  

3.4：login.jsp

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









    

        

      
            

                验证码: