验证码

主要是为了防止暴力攻击

首先创建一个code.html

绑定事件，点击更新验证码


每次加一个随机数 使每次都发新请求，避免读取缓存。


主要配置如上

再创建CodeServlet----------绑定路径为/code

这个验证码代码比较复杂，不要求记忆，可直接百度搜索，进行修改即可。

package cn.zzu.edu.cn;


import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
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;


public class CodeServlet extends HttpServlet {


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


// 使用java图形界面技术绘制一张图片


int charNum = 4;
int width = 30 * 4;
int height = 30;


// 1. 创建一张内存图片
BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);


// 2.获得绘图对象
Graphics graphics = bufferedImage.getGraphics();


// 3、绘制背景颜***r>

graphics.setColor(Color.YELLOW);

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


// 4、绘制图片边框
graphics.setColor(Color.BLUE);
graphics.drawRect(0, 0, width - 1, height - 1);


// 5、输出验证码内容
graphics.setColor(Color.RED);
graphics.setFont(new Font("宋体", Font.BOLD, 20));


// 随机输出4个字符
Graphics2D graphics2d = (Graphics2D) graphics;
String s = "ABCDEFGHGKLMNPQRSTUVWXYZ23456789";
Random random = new Random();
// session中要用到
String msg = "";
int x = 5;
for (int i = 0; i < 4; i++) {
int index = random.nextInt(32);
String content = String.valueOf(s.charAt(index));
msg += content;
double theta = random.nextInt(45) * Math.PI / 180;
// 让字体扭曲
graphics2d.rotate(theta, x, 18);
graphics2d.drawString(content, x, 18);
graphics2d.rotate(-theta, x, 18);
x += 30;
}


// 6、绘制干扰线
graphics.setColor(Color.GRAY);
for (int i = 0; i < 5; i++) {
int x1 = random.nextInt(width);
int x2 = random.nextInt(width);


int y1 = random.nextInt(height);
int y2 = random.nextInt(height);
graphics.drawLine(x1, y1, x2, y2);
}


// 释放资源
graphics.dispose();


// 图片输出 ImageIO
ImageIO.write(bufferedImage, "jpg", response.getOutputStream());

}

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


}


}