用户登录图片验证的实现---基于servlet

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 javax.servlet.http.HttpSession;

public class CheckcodeServlet extends HttpServlet {
/**
* 版本号
*/
private static final long serialVersionUID = 1L;
private int WIDTH=80;
private int HEIGHT=30;
private String getNumber(int size){
String str="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
String rst="";
Random r=new Random();
for(int i=0;i<size;i++){
rst+=str.charAt(r.nextInt(str.length()));
}
return rst;
}
public void service(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
//1.添加画布
BufferedImage image=new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
//2.获得画笔
Graphics g=image.getGraphics();
//3.给笔上色
Random r=new Random();
g.setColor(new Color(r.nextInt(255),r.nextInt(255),r.nextInt(255)));
//4.给画布一个背景色
g.fillRect(0, 0, WIDTH, HEIGHT);//矩形
//5.绘图
//String num=r.nextInt(99999)+"";
String num="";
for(int i=0;i<5;i++){
int h=(int)(10+20*r.nextDouble());
String ch=getNumber(1);
g.setColor(new Color(r.nextInt(255),r.nextInt(255),r.nextInt(255)));
//Font(字体类型，字体风格，高度)
g.setFont(new Font(null,Font.BOLD|Font.ITALIC,18));
num+=ch;
g.drawString(ch, WIDTH/5*i, h);
}
//绑定到session上
HttpSession session=request.getSession();
session.setAttribute("number", num);
//加干扰线
for(int i=0;i<5;i++){
g.setColor(new Color(r.nextInt(255),r.nextInt(255),r.nextInt(255)));
g.drawLine(r.nextInt(80), r.nextInt(30), r.nextInt(80), r.nextInt(30));
}
//6.压缩并发送到客户端
response.setContentType("image/jpeg");
//获得字节输出流
OutputStream os=response.getOutputStream();
//将图片按照指定格式进行压缩，并输出到相应对象

865b
javax.imageio.ImageIO.write(image, "jpeg", os);
}

}
配置好web.xml：
  <servlet>
    <servlet-name>CheckcodeServlet</servlet-name>
    <servlet-class>web.CheckcodeServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>CheckcodeServlet</servlet-name>
    <url-pattern>/checkcode</url-pattern>

  </servlet-mapping>
稍后再登录界面中加入图片验证模块，依据session名称获取进行session验证。