通过response输出认证图片

最新推荐文章于 2024-02-29 23:37:00 发布

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本文介绍了一个使用Java Servlet生成包含随机数字的验证码图片的示例代码。该示例通过设置图片背景、添加随机线条及数字来提高验证码的安全性，并详细展示了如何通过Servlet向浏览器输出生成的JPEG格式验证码图片。

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package com.csdn.response;

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 Response3 extends HttpServlet {

private static final int WIDTH = 130;
private static final int HEIGHT = 30;

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//创建图片
BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_BGR);
//得到图片
Graphics g = image.getGraphics();

//对图片进行绘制
//设置图片的背景颜色
setBackGround(g);
//设置矩形的边框
setBorder(g);
//添加干扰线
setRandomLine(g);
//在图形中写数据
setRandomNum(g);
//把图片写给浏览器
response.setContentType("image/jpeg");

//告诉浏览器不要缓存
response.setHeader("Pragma", "no-cache");
response.setHeader("Cache-Control","no-cache");
response.setIntHeader("Expires",-1);

ImageIO.write(image,"JPEG",response.getOutputStream());
}

private void setRandomNum(Graphics g) {
//数字数据
g.setFont(new Font("宋体",Font.BOLD,20));
Random random = new Random();

int x = 10;
for(int i = 0; i < 4; i++){
//产生随机数
String str = String.valueOf(random.nextInt(10));
g.setColor(new Color(random.nextInt(255),random.nextInt(255),random.nextInt(255)));

int degree = random.nextInt()%30;
((Graphics2D)g).rotate(degree*Math.PI/180, x, 20);
g.drawString(str, x, 20);
((Graphics2D)g).rotate(-degree*Math.PI/180, x, 20);
x +=30;
}

}

private void setRandomLine(Graphics g) {
g.setColor(Color.YELLOW);
Random random = new Random();
for(int i=0; i<5; i++){
int x1 = random.nextInt(WIDTH);
int y1 = random.nextInt(HEIGHT);

int x2 = random.nextInt(WIDTH);
int y2 = random.nextInt(HEIGHT);

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

private void setBorder(Graphics g) {
g.setColor(Color.BLACK);
g.drawRect(1, 1, WIDTH-2, HEIGHT-2);

}

private void setBackGround(Graphics g) {
g.setColor(Color.WHITE);
g.fillRect(0, 0, WIDTH, HEIGHT);

}

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

}