servlet生成随机图片验证码-蒲公英云

servlet生成随机图片验证码

1、代码

package image;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
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;
import javax.servlet.http.HttpSession;
public class ImageCheck extends HttpServlet{ 
    final private int WIDTH=60;//图片的宽
    final private int HEIGHT=30;//图片的高
    final private int CHECKNUMLENGTH=4;//验证码长度
    final private int LINENUM=15;//随即线条数量
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获得图片流
        BufferedImage bi=new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
        //给图片加画笔
        Graphics g=bi.getGraphics();
        //画边框
        g.setColor(Color.white);//背景颜色
        g.fillRect(1, 1, WIDTH-2, HEIGHT-2);//边框
        //g.drawRect(0, 0, WIDTH, HEIGHT);
        //改变字体大小
        g.setFont(new Font(null, Font.BOLD, 20));
        //获得随机数
        String str=random();
        //给图片加上文字
        g.setColor(Color.blue);
        g.drawString(str, 10,22);
        //给图片加上随即线条
        drawRandomLine(g);
        //把文字存储在session中
        HttpSession session = req.getSession();
        session.setAttribute("random", str);
        ImageIO.write(bi, "jpg", resp.getOutputStream());
    }
    /** * 生成随机字符串（数字加字母） */
    private String random() {
        //随机字符生成四位
        Random r=new Random();
        char[] random="1234567890abcdefghijklmopqrstuvwxyz".toCharArray();
        StringBuffer checkstr=new StringBuffer();
        for(int i=0;i<CHECKNUMLENGTH;i++){
            int index=r.nextInt(random.length);
            checkstr.append(random[index]);
        }
        return checkstr.toString();
    }
    /** * 在图片上画随机线条 * @param g */
    private void drawRandomLine(Graphics g) {
       // 设置颜色
       g.setColor(Color.red);
       // 设置线条个数并画线
       for (int i = 0; i < LINENUM; i++) {
          int x1 = new Random().nextInt(WIDTH);
          int y1 = new Random().nextInt(HEIGHT);
          int x2 = new Random().nextInt(WIDTH);
          int y2 = new Random().nextInt(HEIGHT);
           g.drawLine(x1, y1, x2, y2);
       }
    }
}