showrandimageservlet.java

取随机产生的认证码(4位数字) 在内存中创建图象 获取图形上下文 设定背景色 随机产生88个干扰点图象生效 输出图象到页面

package AdminLogin; 
import com.pointbase.session.session;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.imageio.stream.ImageOutputStream;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ShowRandImageServlet extends HttpServlet
{ 
     protected void service(HttpServletRequest request,
                         HttpServletResponse response) throws ServletException,
      IOException {
    // 取随机产生的认证码(4位数字)

    Random random = new Random();
    int randint = random.nextInt(9999);
    String rand =String.valueOf(randint);
    switch (rand.length())
    {

      case 1:
        rand = "000" + rand;
        break;

      case 2:
        rand = "00" + rand;
        break;

      case 3:
        rand = "0" + rand;
        break;

      default:
        rand = rand.substring(0, 4);
        break;

    }
    request.getSession().setAttribute("rand", rand);
    
    // 在内存中创建图象

    int width = 60, height = 18;

    BufferedImage image = new BufferedImage(width, height,
                                            BufferedImage.TYPE_INT_RGB);

// 获取图形上下文

    Graphics g = image.getGraphics();

// 设定背景色

    g.setColor(Color.white);

    g.fillRect(0, 0, width, height);

//画边框

    g.setColor(Color.black);

    g.drawRect(0, 0, width - 1, height - 1);

    g.setColor(Color.BLUE);

    g.setFont(new Font("Times New Roman", Font.PLAIN, 16));

    g.drawString(rand, 10, 14);

// 随机产生88个干扰点

    Random random1 = new Random();

    for (int i = 0; i < 88; i++)

    {

      int x = random1.nextInt(width);

      int y = random1.nextInt(height);

      g.drawLine(x, y, x, y);

    }

// 图象生效

    g.dispose();

// 输出图象到页面

    //ImageOutputStream os = ImageIO.createImageOutputStream(image);
    //byte[] rgb = new byte[ (int) os.length()];
    //os.write(rgb);
    if (image != null) {
      response.setContentType("image/gif");
      OutputStream stream = response.getOutputStream();
      ImageIO.write(image,"JPEG",stream);
      //stream.write(rgb);
    }
    else {
      response.setContentType("text");
      response.getWriter().write("attribute byArr not found");
    }
  }
}