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最近，在弄一个微薄类的sns项目，需要用到验证码，记录下。代码如下，主要是在serlet中实现图片生成，跟随机数，然后把随机数同步到session中

package com.ecar.portal.common.servlet;
import java.io.*;
import java.util.*;
import com.sun.image.codec.jpeg.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.awt.*;
import java.awt.image.*;/*** 功能：调用AuthServlet可以生成一个验证码图片,图片的宽度和高度可以自定义* 调用格式: /servlet/AuthServlet?width=60&height=20*      或者/servlet/AuthServlet* 时间：2010-8-6*  * @author: lyj*/
public class VerifyServlet extends HttpServlet {private Font mFont=new Font("Times New Roman", Font.BOLD,22);//设置字体//static String AuthCode="";// 处理postpublic void doPost(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException {doGet(request,response);}public void doGet(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException {
// 取得一个1000-9999的随机数//System.out.println("servlert方法调用"); HttpSession session=request.getSession();//request.getSession(false)当参数为false时，有可能不创建session//session.setAttribute("getImg",s);response.setContentType("image/gif");response.setHeader("Pragma","No-cache");response.setHeader("Cache-Control","no-cache");response.setDateHeader("Expires", 0);int width=60;int height=20;if(request.getParameter("width")!=null && !request.getParameter("width").equals(""))width = Integer.parseInt(request.getParameter("width"));if(request.getParameter("height")!=null && !request.getParameter("height").equals(""))height = Integer.parseInt(request.getParameter("height"));ServletOutputStream out=response.getOutputStream();BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB); //设置图片大小的Graphics gra=image.getGraphics();Random random=new Random();gra.setColor(getRandColor(233,244));    //设置背景色gra.fillRect(0,0,width,height);gra.setColor(Color.black); //设置字体色gra.setFont(mFont);// 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gra.setColor(getRandColor(160,200));for (int i=0;i<150;i++){int x = random.nextInt(width);int y = random.nextInt(height);int xl = random.nextInt(12);int yl = random.nextInt(12);gra.drawLine(x,y,x+xl,y+yl);}// 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));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gra.drawString(rand,13*i+6,18);}//ystem.out.println("showimage="+sRand);//session.setAttribute("getImg",sRand);session.setAttribute("AuthCode",sRand);//AuthCode = sRand;//session.putValue("AuthCode",sRand);JPEGImageEncoder encoder=JPEGCodec.createJPEGEncoder(out);encoder.encode(image);//out.flush();}static 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);}static public String getAuthCode(HttpSession session){//返回验证return (String)session.getAttribute("AuthCode");}
}