Servlet生成彩色验证码

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

import java.awt.*;
import java.awt.image.*;
import java.util.*;

public class Image extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
response.reset();
response.setContentType(“image/jpeg”);
response.setHeader(“Pragma”,”No-cache”);
response.setHeader(“Cache-Control”,”no-cache”);
response.setDateHeader(“Expires”, 0);

//在内存中创建图象
int width = 58, height = 18;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

//获取图形上下文
Graphics g = image.getGraphics();

//生成随机类
Random random = new Random();

//设定背景色
g.setColor(new Color(201 + random.nextInt(50), 201 + random.nextInt(50), 201 + random.nextInt(50)));
g.fillRect(0, 0, width, height);

//设定字体
g.setFont(new Font(“Times new Roman”, Font.PLAIN, 18));

//画边框
//g.setColor(new Color());
//g.drawRect(0,0,width-1,height-1);

//随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
g.setColor(new Color(160 + random.nextInt(41), 160 + random.nextInt(41),160 + random.nextInt(41)));
for (int i=0;i<155;i++) { int x = random.nextInt(width); int y = random.nextInt(height); int xl = random.nextInt(12); int yl = random.nextInt(12); g.drawLine(x, y, x + xl, y + yl); } //取随机产生的认证码(4位数字) String sRand=""; for (int i = 0; i < 4; i++){ String rand = String.valueOf(random.nextInt(10)); sRand += rand; //将认证码显示到图象中 g.setColor(new Color(20 + random.nextInt(111), 20 + random.nextInt(111),20 + random.nextInt(111))); //调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成 g.drawString(rand, 13 * i + 6, 16); } HttpSession session = null; session = request.getSession(true); //将认证码存入SESSION session.setAttribute("rand", sRand); //图象生效 g.dispose(); //输出图象到页面 //ImageIO.write(image, "JPEG", resp.getOutputStream()); //response.setContentType("image/jpeg"); ServletOutputStream out = response.getOutputStream(); JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out); encoder.encode(image); out.close(); } }