Servlet实现四位数字验证码

以下为在Servlet中实现四位数字验证码的源码分析。 

     
    import java.awt.image.*;

    import com.sun.image.codec.jpeg.*;

    import javax.servlet.*;

    import javax.servlet.http.*;

    import java.io.*;

    import java.util.*;

    import java.awt.*;

    /*

    * 功能：调用AuthCodeServlet可以生成一个4位数字的验证码图片,验证码的图片宽度和高度可以通过配置文件进行定义

    * 验证码调用格式为: /servlet/AuthCodeServlet?w=78&h=32

    * 或者使用默认长宽/servlet/AuthCodeServlet

    */

    public class AuthCodeServlet extends HttpServlet {

    // 处理post

    public void doPost(HttpServletRequest req,HttpServletResponse res)

    throws ServletException,IOException {

    doGet(req,res);

    }

    //设置字体

    private Font mFont=new Font("Times New Roman", Font.PLAIN,16);

    public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException {

    HttpSession session=request.getSession();

    response.setContentType("image/gif");

    response.setHeader("Pragma","No-cache");

    response.setHeader("Cache-Control","no-cache");

    response.setDateHeader("Expires", 0);

    int width=70; //验证码默认长度

    int height=24; //验证码默认宽度

    if(request.getParameter("w")!=null && !request.getParameter("w").equals(""))

    width = Integer.parseInt(request.getParameter("w"));

    if(request.getParameter("h")!=null && !request.getParameter("h").equals(""))

    height = Integer.parseInt(request.getParameter("h"));

    ServletOutputStream out=response.getOutputStream(); //获取输出流

    BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB); //新建验证图片，并设置验证码图片的大小

    Graphics gra=image.getGraphics(); //获取图形上下文

    Random random=new Random();

    gra.setColor(getRandColor(260,210));    //设置验证码的图片背景色

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

    gra.setColor(Color.BLUE); //设置字体色为蓝色

    gra.setFont(mFont); //设置定义的字体格式

    // 随机产生254条干扰直线，使图象中的验证码不易被解析程序分析到

    gra.setColor(getRandColor(110,240));

    for (int i=0;i<254;i++)

    {

    int x = random.nextInt(width);

    int y = random.nextInt(height);

    int xl = random.nextInt(63);

    int yl = random.nextInt(64);

    gra.drawLine(x,y,x+xl,y+yl);

    }

    // 取随机产生的验证码(4位数字)

    String sRand="";

    for (int i=0;i<4;i++){

    String rand=String.valueOf(random.nextInt(353));

    sRand+=rand;

    // 将认证码显示到图象中

    gra.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));

    //调用随机函数构建随机颜色三素

    gra.drawString(rand,13*i+6,16);

    }

    session.setAttribute("authCode",sRand);

    JPEGImageEncoder encoder=JPEGCodec.createJPEGEncoder(out);

    encoder.encode(image);

    }

    static Color getRandColor(int ff,int cc){

    //给定范围获得随机颜色

    Random random = new Random();

    if(fc>255) ff=255;

    if(bc>255) cc=255;

    int r=ff+random.nextInt(cc-ff);

    int g=ff+random.nextInt(cc-ff);

    int b=ff+random.nextInt(cc-ff);

    return new Color(r,g,b);

    }

    static public String getAuthCode(HttpSession session){

    //返回验证码

    return (String)session.getAttribute("AuthCode");

    }

    }