JSP + Servlet實現登錄驗證碼

隨機生成四位數驗證碼，包括漢字，數字，英文大小寫。

1.Servlet類

package servlet;

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;
import java.awt.geom.Line2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
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;
import javax.servlet.http.HttpSession;

public class PictureCheckCode extends HttpServlet {

     private static final long serialVersionUID = 1L;  

        public PictureCheckCode() {  
            super();  
        }  

        public void destroy() {  
            super.destroy();   
        }  

        public void init() throws ServletException {  
            super.init();  
        }  
        /*該方法主要作用是獲得隨機生成的顏色*/   
        public Color getRandColor(int s,int e){  
            Random random=new Random ();  
            if(s>255) s=255;  
            if(e>255) e=255;  
            int r,g,b;  
            r=s+random.nextInt(e-s);    //隨機生成RGB顏色中的r值  
            g=s+random.nextInt(e-s);    //隨機生成RGB顏色中的g值  
            b=s+random.nextInt(e-s);    //隨機生成RGB顏色中的b值  
            return new Color(r,g,b);  
        }  

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println("this is doGet method");
        this.doPost(request, response);

    }

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

        //設置不緩存圖片  
        response.setHeader("Pragma", "No-cache");  
        response.setHeader("Cache-Control", "No-cache");  
        response.setDateHeader("Expires", 0);  
        //指定生成的響應圖片,一定不能缺少這句話,否則錯誤.  
        response.setContentType("image/jpeg");  
        int width=80,height=35;     //指定生成驗證碼的寬度和高度  
        BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB); //創建BufferedImage對象,其作用相當於一圖片  
        Graphics g=image.getGraphics();     //創建Graphics對象,其作用相當於畫筆  
        Graphics2D g2d=(Graphics2D)g;       //創建Grapchics2D對象  
        Random random=new Random();  
        Font mfont=new Font("楷體",Font.BOLD,16); //定義字體樣式  
        g.setColor(getRandColor(200,250));  
        g.fillRect(0, 0, width, height);    //繪製背景  
        g.setFont(mfont);                   //設置字體  
        g.setColor(getRandColor(180,200));  

        //繪製100條顏色和位置全部爲隨機產生的線條,該線條爲2f  
        for(int i=0;i<100;i++){  
            int x=random.nextInt(width-1);  
            int y=random.nextInt(height-1);  
            int x1=random.nextInt(6)+1;  
            int y1=random.nextInt(12)+1;  
            BasicStroke bs=new BasicStroke(2f,BasicStroke.CAP_BUTT,BasicStroke.JOIN_BEVEL); //定製線條樣式  
            Line2D line=new Line2D.Double(x,y,x+x1,y+y1);  
            g2d.setStroke(bs);  
            g2d.draw(line);     //繪製直線  
        }  
        //輸出由英文，數字，和中文隨機組成的驗證文字，具體的組合方式根據生成隨機數確定。  
        String sRand="";  
        String ctmp="";  
        int itmp=0;  
        //制定輸出的驗證碼爲四位  
        for(int i=0;i<4;i++){  
            switch(random.nextInt(3)){  
                case 1:     //生成A-Z的字母  
                     itmp=random.nextInt(26)+65;  
                     ctmp=String.valueOf((char)itmp);  
                     break;  
                case 2:     //生成漢字  
                     String[] rBase={"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"};   
                     //生成第一位區碼  
                     int r1=random.nextInt(3)+11;  
                     String str_r1=rBase[r1];  
                     //生成第二位區碼  
                     int r2;  
                     if(r1==13){  
                         r2=random.nextInt(7);     
                     }else{  
                         r2=random.nextInt(16);  
                     }  
                     String str_r2=rBase[r2];  
                     //生成第一位位碼  
                     int r3=random.nextInt(6)+10;  
                     String str_r3=rBase[r3];  
                     //生成第二位位碼  
                     int r4;  
                     if(r3==10){  
                         r4=random.nextInt(15)+1;  
                     }else if(r3==15){  
                         r4=random.nextInt(15);  
                     }else{  
                         r4=random.nextInt(16);  
                     }  
                     String str_r4=rBase[r4];  
                     //將生成的機內碼轉換爲漢字  
                     byte[] bytes=new byte[2];  
                     //將生成的區碼保存到字節數組的第一個元素中  
                     String str_12=str_r1+str_r2;  
                     int tempLow=Integer.parseInt(str_12, 16);  
                     bytes[0]=(byte) tempLow;  
                     //將生成的位碼保存到字節數組的第二個元素中  
                     String str_34=str_r3+str_r4;  
                     int tempHigh=Integer.parseInt(str_34, 16);  
                     bytes[1]=(byte)tempHigh;  
                     ctmp=new String(bytes);  
                     break;  
                default:  
                     itmp=random.nextInt(10)+48;  
                     ctmp=String.valueOf((char)itmp);  
                     break;  
            }  
            sRand+=ctmp;  
            Color color=new Color(20+random.nextInt(110),20+random.nextInt(110),random.nextInt(110));  
            g.setColor(color);  
            //將生成的隨機數進行隨機縮放並旋轉制定角度 PS.建議不要對文字進行縮放與旋轉,因爲這樣圖片可能不正常顯示  
            /*將文字旋轉制定角度*/  
            Graphics2D g2d_word=(Graphics2D)g;  
            AffineTransform trans=new AffineTransform();  
            trans.rotate((45)*3.14/180,15*i+8,7);  
            /*縮放文字*/  
            float scaleSize=random.nextFloat()+0.8f;  
            if(scaleSize>1f) scaleSize=1f;  
            trans.scale(scaleSize, scaleSize);  
            g2d_word.setTransform(trans);  
            g.drawString(ctmp, 15*i+18, 14);  
        }  
        HttpSession session=request.getSession(true);  
        session.setAttribute("randCheckCode", sRand);  
        System.out.println(sRand);
        g.dispose();    //釋放g所佔用的系統資源  
        ImageIO.write(image,"JPEG",response.getOutputStream()); //輸出圖片  
    }

}

2.web.xml配置

<servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>PictureCheckCode</servlet-name>
    <servlet-class>servlet.PictureCheckCode</servlet-class>
  </servlet>

<servlet-mapping>
    <servlet-name>PictureCheckCode</servlet-name>
    <url-pattern>/pictureCheckCode</url-pattern>
  </servlet-mapping>

3.jsp頁面輸出驗證碼

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>

<title>登錄頁面</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<script language="javascript">
    function myReload() {
        document.getElementById("CreateCheckCode").src = document
                .getElementById("CreateCheckCode").src
                + "?nocache=" + new Date().getTime();
    }
</script>

</head>

<body>
    <form action="loginServlet" method="get">
            <p class="font tdheight">
                驗證碼：<input type="text" name="checkCode"
                    style="width:70px;height:35px;"> <img
                    src="pictureCheckCode" id="CreateCheckCode" align="middle"
                    style="margin-top:-10px;"> <br> <a href=""
                    onclick="myReload()"
                    style="font-size:12px;color:red;margin-left:156px;"> 看不清,換一個</a>
            </p>
            <br><input type="submit" value="提交"
                        class="font" style="width:240px;height:35px;background:#f19e28">

        </form>
</body>
</html>

4.後臺Servlet判斷驗證碼是否與輸入一致
通過request.getParameter(“checkCode”)獲取輸入驗證碼，與session.getAttribute(“randCheckCode”)比較是否一致。

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

        String code = request.getParameter("checkCode");
        HttpSession session = request.getSession();
        if (!code.equals(session.getAttribute("randCheckCode"))) {
            request.setAttribute("errormsg", "驗證碼不正確");
        } 
        System.out.println(request.getAttribute("errormsg"));
    }

運行結果：