验证码生成（servlet）

　　一 效果如下：

　　　　

　　二 java 代码如下：

　　　　　　　

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/DrawImg")
public class DrawImg extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public static final int WIDTH = 140;
    public static final int HEIGHT = 35;
    public static int RANDOMSTARTPOSITION=20;
    
    public DrawImg() {
        super();
    }

    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }

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

        String createTypeFlag = request.getParameter("createTypeFlag");

        BufferedImage bi = new BufferedImage(WIDTH, HEIGHT,
                BufferedImage.TYPE_INT_RGB);

        Graphics g = bi.getGraphics();

        // background
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, WIDTH, HEIGHT);

        // border
        g.setColor(Color.BLUE);
        g.drawRect(1, 1, WIDTH - 2, HEIGHT - 2);

        // randomLines
        g.setColor(Color.GREEN);

        for (int i = 0; i < 5; i++) {
            int x1 = new Random().nextInt(WIDTH);
            int y1 = new Random().nextInt(HEIGHT);
            int x2 = new Random().nextInt(WIDTH);
            int y2 = new Random().nextInt(HEIGHT);
            g.drawLine(x1, y1, x2, y2);

        }

        String random = drawRandomNum((Graphics2D) g, createTypeFlag);

        request.getSession().setAttribute("checkCode", random);
        response.setContentType("image/jpeg");

        // noCache
        response.setDateHeader("expries", -1);
        response.setHeader("Cache-Control", "no-cache");
        response.setHeader("Pragma", "no-cache");

        ImageIO.write(bi, "jpg", response.getOutputStream());
    }

    private String drawRandomNum(Graphics2D g, String... createTypeFlag) {

        g.setColor(Color.RED);
        g.setFont(new Font("隶书", Font.BOLD, 16));

        // 常用汉字编码
        String baseChineseChar = "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";
        String baseNumLetter = "0123456789ABCDEFGHJKLMNOPQRSTUVWXYZ";
        String baseNum = "0123456789";
        String baseLetter = "ABCDEFGHJKLMNOPQRSTUVWXYZ";

        String baseChar = baseNumLetter;

        if (createTypeFlag.length > 0 && null != createTypeFlag[0]) {

            if (createTypeFlag[0].equals("ch")) { // 汉字

                baseChar = baseChineseChar;

            } else if (createTypeFlag[0].equals("nl")) { // 字母和数字

                baseChar = baseNumLetter;

            } else if (createTypeFlag[0].equals("n")) { // 数字

                baseChar = baseNum;

            } else if (createTypeFlag[0].equals("l")) { // 字母

                baseChar = baseLetter;
            }
        }

        return createRandomChar(g, baseChar);

    }

    private String createRandomChar(Graphics2D g, String baseChar) {
        
        StringBuffer sb = new StringBuffer();
        String ch = "";
        int x=RANDOMSTARTPOSITION;
        
        for (int i = 0; i < 4; i++) {

            ch = baseChar.charAt(new Random().nextInt(baseChar.length())) + "";
            sb.append(ch);

            int degree = new Random().nextInt() % 30;
            g.rotate(degree * Math.PI / 180, x, 20);
            g.drawString(ch, x, 20);
            g.rotate(-degree * Math.PI / 180, x, 20);
            x += 30;
        }
        return sb.toString();
    }

}

　　三 html代码如下：

　　　　

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>

<style>

body{
    margin:0;
    padding:0;
    font-size:12px;
}
#container {
    text-align:center;
    
    margin: 50px auto;
}

table td{

    border:1px solid #000;
    padding:10px 20px;
    
}

</style>
</head>
<body>
        <table  id="container"  cellspacing="0"  style="border-collapse:collapse;">
         <thead>
             <tr>
                 <td>验证码类型</td>
                 <td>Display</td>
                 <td>参数类型</td>
             </tr>
         </thead>
         <tbody>
             <tr>
                 <td>默认：</td>
                 <td><img src="DrawImg"/></td>
                 <td></td>
             </tr>
             <tr>
                 <td>汉字：</td>
                 <td><img src="DrawImg?createTypeFlag=ch"/></td>
                 <td>?createTypeFlag=ch</td>
             </tr>
             <tr>
                 <td>字母数字：</td>
                 <td><img src="DrawImg?createTypeFlag=nl"/></td>
                 <td>?createTypeFlag=nl</td>
             </tr>
             <tr>
                 <td>数字：</td>
                 <td><img src="DrawImg?createTypeFlag=n"/></td>
                 <td>?createTypeFlag=n</td>
             </tr>
             <tr>
                 <td>字母：</td>
                 <td><img src="DrawImg?createTypeFlag=l"/></td>
                 <td>?createTypeFlag=l</td>
             </tr>
         </tbody>
        </table>
</body>
</html>

　　四 总结：

　　　　生成验证码图片主要用到了一个BufferedImage类 ，源码下载：百度网盘