生成二维码



package com.libo.util;

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.io.OutputStream;

import javax.imageio.ImageIO;

import com.google.zxing.common.BitMatrix;
/**
 * 这个类是提供的工具类
 *
 */
public class MatrixToImageWriter {
 private static final int BLACK = 0xFF000000;
    private static final int WHITE = 0xFFFFFFFF;
 
    private MatrixToImageWriter() {}
 
   
    public static BufferedImage toBufferedImage(BitMatrix matrix) {
      int width = matrix.getWidth();
      int height = matrix.getHeight();
      BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
      for (int x = 0; x < width; x++) {
        for (int y = 0; y < height; y++) {
          image.setRGB(x, y, matrix.get(x, y) ? BLACK : WHITE);
        }
      }
      return image;
    }
 
   
    public static void writeToFile(BitMatrix matrix, String format, File file)
        throws IOException {
      BufferedImage image = toBufferedImage(matrix);
      if (!ImageIO.write(image, format, file)) {
        throw new IOException("Could not write an image of format " + format + " to " + file);
      }
    }
 
   
    public static void writeToStream(BitMatrix matrix, String format, OutputStream stream)
        throws IOException {
      BufferedImage image = toBufferedImage(matrix);
      if (!ImageIO.write(image, format, stream)) {
        throw new IOException("Could not write an image of format " + format);
      }
    }

}

************************************************************************************************

 <form action="student/logins.action" method="post">
     用户名:<input name="name"><br/>
     密码:<input type="password" name="pwd"><br/>
     验证码:<input type="text" name="code"> <img id="img" alt="二维码" src="student/code.action" onclick="ghewm()">
     <input type="submit" value="提交">
    </form>