动手实现随机验证码

见过好几种类型的验证码，一开始觉得验证码的生成很神奇，后来发现验证码也是可以用Java轻松实现的。今天就来做一做这件事情。

首先，来写一个画验证码图片的Java类：

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package com.xxx.validationCode;   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.imageio.ImageIO; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;   public class ValidationCode extends HttpServlet{           public static String getValidationCodes(OutputStream os){         char codeTable[]={                 'a','b','c','d','e','f','g','h','i','j','k','l',                 'm','n','p','q','r','s','t','u','v','w','x','y','z',                 'A','B','C','D','E','F','G','H','I','J','K','L',                 'M','N','P','Q','R','S','T','U','V','W','X','Y','Z',                 '1','2','3','4','5','6','7','8','9'             };    //判断时大小写不区分，另外，没有使用'O'和'0'，也是怕混淆的麻烦                      BufferedImage image = new BufferedImage(60, 20,                                     BufferedImage.TYPE_INT_RGB);         //生成60×20的RGB图片         Graphics graphic = image.getGraphics();         //背景色         graphic.setColor(new Color(0xDCDCDC));         graphic.fillRect(0, 0, 60, 20);                   char codes[] = new char[4];         //随机产生验证码         for(int i=0; i<=3; i++) {             codes[i] = codeTable[(int)(codeTable.length*Math.random())];         }                   //把字画上去         graphic.setColor(Color.BLACK);         graphic.setFont(new Font("Arial", Font.BOLD, 16));         for(int i=0; i<=3; i++){             graphic.drawChars(codes, i, 1, 2+15*i, 15+i);             //把codes[i]画到坐标为[10+5*i,15+i]的地方去         }                   //15个干扰点         Random rand = new Random();         for (int i=0;i<15;i++)             graphic.drawOval(rand.nextInt(60),rand.nextInt(20),1,1);                   //释放此图形的上下文并释放它所使用的所有系统资源         graphic.dispose();                   try {             ImageIO.write(image, "JPEG", os);         } catch (IOException e) {             e.printStackTrace();         }                   return new String(codes,0,codes.length);     }       public void doGet(HttpServletRequest request, HttpServletResponse response)             throws ServletException, IOException {         doPost(request,response);     }       public void doPost(HttpServletRequest request, HttpServletResponse response)             throws ServletException, IOException {         request.getSession().setAttribute("validationCodes", getValidationCodes(response.getOutputStream()));     }       }

然后，写一个Servlet将生成的图片写入页面：

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package com.xxx.servlet;   import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;   import com.xxx.validationCode.ValidationCode;   public class ValidationServlet extends HttpServlet {       public void doGet(HttpServletRequest request, HttpServletResponse response)             throws ServletException, IOException {         doPost(request,response);     }       public void doPost(HttpServletRequest request, HttpServletResponse response)             throws ServletException, IOException {         String str = ValidationCode.getValidationCodes(response.getOutputStream());         request.getSession().setAttribute("validationCodes", str);     }   }

接着，在login.jsp中加入如下表单：

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<% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %>   <form action="<%=basePath+"servlet/LoginServlet"%>">     <img src="<%=basePath+"servlet/ValidationServlet"%>"/>     <br>     <input type="text" name="codes"/>     <input type="submit"/> </form>

再写进行后台判断的Servlet：

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package com.xxx.servlet;   import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;   public class LoginServlet extends HttpServlet {     public void doGet(HttpServletRequest request, HttpServletResponse response)             throws ServletException, IOException {         doPost(request,response);     }     public void doPost(HttpServletRequest request, HttpServletResponse response)             throws ServletException, IOException {           if(request.getSession().getAttribute("validationCodes").toString().toLowerCase()                     .equals(request.getParameter("codes").toString().toLowerCase()))             response.getOutputStream().println("Right!");         else             response.getOutputStream().println("Wrong!");               }   }

转载自《四火的唠叨》