verifycode.java

用Servlet生成4位数字的图片验证码 功能： 1 取得一个1000-9999的随机数 2 设置图片大小 3 设置背景色 4 设置字体色 5 随机产生155条干扰线

package util;

import java.io.*;
import java.util.*;
import com.sun.image.codec.jpeg.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.awt.*;
import java.awt.image.*;

public class VerifyCode extends HttpServlet {

    private Font mFont = new Font("Times New Roman", Font.PLAIN, 18); //设置字体

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

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws
            ServletException, IOException {
//取得一个1000-9999的随机数


        HttpSession session = request.getSession(false);
//session.setAttribute("getImg",s);
        response.setContentType("image/gif");
        response.setHeader("Pragma", "No-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        int width = 60, height = 20;

        ServletOutputStream out = response.getOutputStream();
        BufferedImage image = new BufferedImage(width, height,
                                                BufferedImage.TYPE_INT_RGB); //设置图片大小的
        Graphics gra = image.getGraphics();
        Random random = new Random();

        gra.setColor(getRandColor(200, 250)); //设置背景色
        gra.fillRect(0, 0, width, height);

        gra.setColor(Color.black); //设置字体色
        gra.setFont(mFont);

        /* gra.setColor(new Color(0));
         gra.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
        gra.setColor(getRandColor(160, 200));
        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);
            gra.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
            gra.setColor(new Color(20 + random.nextInt(110),
                                   20 + random.nextInt(110),
                                   20 + random.nextInt(110))); //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
            gra.drawString(rand, 13 * i + 6, 16);
        }
//System.out.println("showimage="+sRand);
// session.setAttribute("getImg", sRand);
        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
        encoder.encode(image);
        out.close();

    }

    static Color getRandColor(int fc, int bc) { //给定范围获得随机颜色
        Random random = new Random();
        if (fc > 255) {
            fc = 255;
        }
        if (bc > 255) {
            bc = 255;
        }
        int r = fc + random.nextInt(bc - fc);
        int g = fc + random.nextInt(bc - fc);
        int b = fc + random.nextInt(bc - fc);
        return new Color(r, g, b);
    }


}