用JSP文件生成网站验证码


答案：random.jsp文件代码:

<%@ page autoFlush="false"  import="java.awt.*,java.awt.image.*,com.sun.image.codec.jpeg.*,java.util.*"%>
<%@ page import="org.apache.commons.lang.RandomStringUtils"%>
<% 
RandomStringUtils rs=new RandomStringUtils();
String random=rs.randomAlphanumeric(4);
session.setAttribute("random",random);
 %>
<%

        out.clear();
        response.setContentType("image/jpeg");
        response.addHeader("pragma","NO-cache");
        response.addHeader("Cache-Control","no-cache");
        response.addDateHeader("Expries",0);
        int width=100, height=40;
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics g = image.getGraphics();
        //以下填充背景?色
        g.setColor(Color.GRAY);
        Font DeFont=new Font("SansSerif", Font.PLAIN, 32); 
        g.setFont(DeFont);
        g.fillRect(0, 0, width, height);
       //?置字体?色
        g.setColor(Color.RED);
        g.drawString(random,3,30);
        g.dispose();
        ServletOutputStream outStream = response.getOutputStream();
        JPEGImageEncoder encoder =JPEGCodec.createJPEGEncoder(outStream);
        encoder.encode(image);
        outStream.close();
   %>

test.jsp文件代码如下:
<%@ page contentType="text/html; charset=UTF-8" language="java" import="java.sql.*" errorPage="" %>
<html>
<head>
<title>Untitled Document</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
</head>

<body>
<img src="random.jsp"> 
</body>
</html>

如果不想导入Apache的包可以自己编译下面这个文件
// FrontEnd Plus GUI for JAD
// DeCompiled : RandomStringUtils.class

package org.apache.commons.lang;

import java.util.Random;

public class RandomStringUtils
{

    private static final Random RANDOM = new Random();

    public RandomStringUtils()
    {
    }

    public static String random(int count)
    {
        return random(count, false, false);
    }

    public static String randomAscii(int count)
    {
        return random(count, 32, 127, false, false);
    }

    public static String randomAlphabetic(int count)
    {
        return random(count, true, false);
    }

    public static String randomAlphanumeric(int count)
    {
        return random(count, true, true);
    }

    public static String randomNumeric(int count)
    {
        return random(count, false, true);
    }

    public static String random(int count, boolean letters, boolean numbers)
    {
        return random(count, 0, 0, letters, numbers);
    }

    public static String random(int count, int start, int end, boolean letters, boolean numbers)
    {
        return random(count, start, end, letters, numbers, null);
    }

    public static String random(int count, int start, int end, boolean letters, boolean numbers, char set[])
    {
        if(start == 0 && end == 0)
        {
            end = 122;
            start = 32;
            if(!letters && !numbers)
            {
                start = 0;
                end = 0x7fffffff;
            }
        }
        StringBuffer buffer = new StringBuffer();
        int gap = end - start;
        while(count-- != 0) 
        {
            char ch;
            if(set == null)
                ch = (char)(RANDOM.nextInt(gap) + start);
            else
                ch = set[RANDOM.nextInt(gap) + start];
            if(letters && numbers && Character.isLetterOrDigit(ch) || letters && Character.isLetter(ch) || numbers && Character.isDigit(ch) || !letters && !numbers)
                buffer.append(ch);
            else
                count++;
        }
        return buffer.toString();
    }

    public static String random(int count, String set)
    {
        return random(count, set.toCharArray());
    }

    public static String random(int count, char set[])
    {
        return random(count, 0, set.length - 1, false, false, set);
    }

}
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