java随机验证码的生成

来源：互联网发布：sql语言有两种使用方式编辑：程序博客网时间：2024/04/28 23:27

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Date;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

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

/**
* Servlet implementation class for Servlet: ImageGenerator
*
*/
public class ImageGenerator extends javax.servlet.http.HttpServlet implements
        javax.servlet.Servlet {
    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("image/jpeg"); // 必须设置ContentType为image/jpeg
        int length = 4; // 设置默认生成4个数字
        Date d = new Date();
        long lseed = d.getTime();
        Random r = new Random(lseed); // 设置随机种子
        if (request.getParameter("length") != null) {
            try {
                length = Integer.parseInt(request.getParameter("length"));
            } catch (NumberFormatException e) {
            }
        }

        // 可以在此加入保存验证码的代码
        // 创建内存图像
        BufferedImage bi = ImageIO.read(new File(this.getServletContext().getRealPath("./imgc.jpg")));
        //可以在上面读入一个背景图，然后在背景图上写数字

        Graphics2D g = bi.createGraphics();
        g.setColor(Color.CYAN);
        g.setFont(new Font(null, Font.BOLD, 15));
        //旋转
        double rot;

        for (int i = 0; i < length; i++) {
            g.drawString(String.valueOf(r.nextInt(9)), bi.getWidth()/4 + i * 15, bi.getHeight()/2);
            rot = r.nextDouble() * 0.1;
            if(r.nextBoolean())
                rot = -1 * rot;
            g.rotate(rot);
        }

        try {
            // 使用JPEG编码，输出到response的输出流
            JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(response
                    .getOutputStream());
            JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(bi);
            param.setQuality(1.0f, false);
            encoder.setJPEGEncodeParam(param);
            encoder.encode(bi);
        } catch (Exception ex) {
        }
    }
}