验证码

html页面

<img  align="absbottom" src="/yzm" width="66" height="22" />

web.xml配置servlet

<servlet>
            <servlet-name>yzm</servlet-name>
            <servlet-class>com.fun.yzm</servlet-class>
     </servlet>
        
    <servlet-mapping> 
     <servlet-name>yzm</servlet-name> 
    <url-pattern>/yzm</url-pattern> 
      </servlet-mapping> 

java代码

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.awt.*;
import java.awt.image.*;
import java.util.*;
import javax.imageio.*;
 
/**
*
* @author http://www.tot.name
* @version
*/ 
public class yzm extends HttpServlet {

/** Processes requests for both HTTP <code>GET</code> and <code>POST
</code> methods.
* @param request servlet request
* @param response servlet response
*/
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
	response.setContentType("image/jpeg;charset=GB2312");
	response.setHeader("Pragma","No-cache");
	response.setHeader("Cache-Control","no-cache");
	response.setDateHeader("Expires", 0); 
	HttpSession session=request.getSession();
	// 在内存中创建图象
	int width=60, height=20;
	BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
	
	// 获取图形上下文
	Graphics g = image.getGraphics();
	
	//生成随机类
	Random random = new Random();

	// 设定背景色
	g.setColor(getRandColor(200,250));
	g.fillRect(0, 0, width, height);
	
	//设定字体
	g.setFont(new Font("Times New Roman",Font.PLAIN,18));

	//画边框
	//g.setColor(new Color());
	//g.drawRect(0,0,width-1,height-1);
	
	
	// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
	g.setColor(getRandColor(160,200));
	for (int i=0;i<155;i++) {
		int x = random.nextInt(width);
		int y = random.nextInt(height);
		int xl = random.nextInt(12);
		int yl = random.nextInt(12);
		g.drawLine(x,y,x+xl,y+yl);
	}

//	String str = "妈妈说验证用中文最好";
//	String[] strs = str.split("");
	// 取随机产生的认证码(4位数字)
	String sRand="";
	for (int i=0;i<4;i++){
		String rand=String.valueOf(random.nextInt(10));
//		String rand = strs[random.nextInt(10)];
		sRand+=rand;
		// 将认证码显示到图象中
		g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
		g.drawString(rand,13*i+6,16);
	}

	// 将认证码存入SESSION
 
	session.setAttribute("rand",sRand);
	// 	图象生效
	g.dispose();
	ServletOutputStream responseOutputStream =response.getOutputStream();
	// 输出图象到页面
	ImageIO.write(image, "JPEG", responseOutputStream);

	//以下关闭输入流！
	responseOutputStream.flush();
	responseOutputStream.close();
}

Color getRandColor(int fc,int bc){//给定范围获得随机颜色
	Random random = new Random();
	if(fc>255) fc=255;
	if(bc>255) bc=255;
	int r=fc+random.nextInt(bc-fc);
	int g=fc+random.nextInt(bc-fc);
	int b=fc+random.nextInt(bc-fc);
	return new Color(r,g,b);
}

// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/** Handles the HTTP <code>GET</code> method.
* @param request servlet request
* @param response servlet response
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
	processRequest(request, response);
}

/** Handles the HTTP <code>POST</code> method.
* @param request servlet request
* @param response servlet response
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
	processRequest(request, response);
}

/** Returns a short description of the servlet.
*/
public String getServletInfo() {
	return "Short description";
}
// </editor-fold>
}