java web 生成图片验证码的功能实现

1.前台页面

验证码:

换一张

2.后台servlet代码

package web;
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.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
public class CheckCodeServlet extends HttpServlet {
public void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println("service...");
//生成一张图片
Random r = new Random(
System.currentTimeMillis());
//随机字符串
String value = r.nextInt(999999) + "";
//先创建一个内存映像对象
BufferedImage image = 
new BufferedImage(80,30,
BufferedImage.TYPE_INT_RGB);
//得到画笔
Graphics g = image.getGraphics();
g.setColor(new Color(r.nextInt(255),
r.nextInt(255),r.nextInt(255)));
//填充
g.fillRect(0, 0, 80, 30);
//画画
g.setColor(new Color(0,0,0));
//Font(String,int,int); 字体名称，风格，大小
g.setFont(new Font(null,Font.BOLD,18));
g.drawString(value, 5, 20);
for(int i=0;i<8;i++){
g.drawLine(r.nextInt(80), r.nextInt(30),
r.nextInt(80), r.nextInt(30));
}

//将图片压缩
//需要提供一个输出流,encoder工具会将
//图片压缩之后的数据以流的方式输出。
response.setContentType("image/jpeg");
OutputStream ops = 
response.getOutputStream();
javax.imageio.ImageIO.write(
image, "jpg", ops);
}
}

3.web.xml的配置

      CheckCodeServlet
      web.CheckCodeServlet
  
  
      CheckCodeServlet
      /checkcode