Servlet简单实现动态验证码

servlet部分：

 import java.awt.Color;
 import java.awt.Font;
 import java.awt.Graphics2D;
 import java.awt.image.BufferedImage;
 import java.io.IOException;
 import javax.imageio.ImageIO;
 import javax.servlet.ServletException;
 import javax.servlet.annotation.WebServlet;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse
 /**
  * Servlet implementation class RandomPassword
  */
 @WebServlet("/rp.do")
 public class RandomPassword extends HttpServlet {
 private static final long serialVersionUID = 1L;

/**
 * @see HttpServlet#HttpServlet()
 */
public RandomPassword() {
    super();
    // TODO Auto-generated constructor stub
}
protected void processRequest(HttpServletRequest request,HttpServletResponse response)throws Exception{
    response.setContentType("image/jpeg");    //设置页面输出格式
    BufferedImage bi=new BufferedImage(100,80,BufferedImage.TYPE_INT_RGB);
        Graphics2D g=bi.createGraphics();
        StringBuilder sb=new StringBuilder();   //创建验证码字符串
        for(int i=0;i<4;i++){
        sb.append((int)(Math.random()*9));   //将随机验证码加入字符串
        
    }
    request.getSession().setAttribute("random", sb.toString());   //将验证码保存，以便以后验证
    g.fillRect(0, 0, 100, 80);   //设置绘制区域（默认颜色为白色）
    Font font=new Font("宋体",Font.BOLD,30);   //设置字体格式
    g.setFont(font);
    g.setColor(Color.black);
    g.drawString(sb.toString(), 20, 40);     
    ImageIO.write(bi, "jpeg", response.getOutputStream());   //输出验证码图片
    response.getOutputStream().flush();
    response.getOutputStream().close();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    try {
        processRequest(request,response);
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    try {
        processRequest(request,response);
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}
  }

Html部分：

  






![](rp.do)        //设置验证码路径
输入图片上的密码：
提交