java实现验证码功能

在实现这个功能之前先简单了解一下

BufferedImage类

Graphics类

ImageIO类

有助于理解
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 效果图：

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验证码实现类：

package com.tools;

import java.awt.Color;

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

/**
 * 验证码生成器
 * 
 */
public class VCodeGenerator {
    
    /**
     * 验证码来源
     */
    final private char[] code = {
        '2', '3', '4', '5', '6', '7', '8', '9',
        'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
        'k', 'm', 'n', 'p', 'q', 'r', 's', 't', 'u', 'v', 
        'w', 'x', 'y', 'z', 'A', 'B', 'C', 'D', 'E', 'F',
        'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'Q', 'R',
        'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'
    };
    /**
     * 字体
     */
    final private String[] fontNames = new String[]{
            "黑体", "宋体", "Courier", "Arial", 
            "Verdana", "Times", "Tahoma", "Georgia"};
    /**
     * 字体样式
     */
    final private int[] fontStyles = new int[]{
            Font.BOLD, Font.ITALIC|Font.BOLD
    };
    
    /**
     * 验证码长度
     * 默认4个字符
     */
    private int vcodeLen = 4;
    /**
     * 验证码图片字体大小
     * 默认17
     */
    private int fontsize = 21;
    /**
     * 验证码图片宽度
     */
    private int width = (fontsize+1)*vcodeLen+10;
    /**
     * 验证码图片高度
     */
    private int height = fontsize+12;
    /**
     * 干扰线条数
     * 默认3条
     */
    private int disturbline = 3;
    
    
    public VCodeGenerator(){}
    
    /**
     * 指定验证码长度
     * @param vcodeLen 验证码长度
     */
    public VCodeGenerator(int vcodeLen) {
        this.vcodeLen = vcodeLen;
        this.width = (fontsize+1)*vcodeLen+10;
    }
    
    /**
     * 生成验证码图片
     * @param vcode 要画的验证码
     * @param drawline 是否画干扰线
     * @return
     */
    public BufferedImage generatorVCodeImage(String vcode, boolean drawline){
        //创建验证码图片
        BufferedImage vcodeImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
        Graphics g = vcodeImage.getGraphics();
        //填充背景色
        g.setColor(new Color(246, 240, 250));
        g.fillRect(0, 0, width, height);
        if(drawline){
            drawDisturbLine(g);
        }
        //用于生成伪随机数
        Random ran = new Random();
        //在图片上画验证码
        for(int i = 0;i < vcode.length();i++){
            //设置字体
            g.setFont(new Font(fontNames[ran.nextInt(fontNames.length)], fontStyles[ran.nextInt(fontStyles.length)], fontsize));
            //随机生成颜色
            g.setColor(getRandomColor());
            //画验证码
            g.drawString(vcode.charAt(i)+"", i*fontsize+10, fontsize+5);
        }
        //释放此图形的上下文以及它使用的所有系统资源
        g.dispose();
        
        return vcodeImage;
    }
    /**
     * 获得旋转字体的验证码图片
     * @param vcode
     * @param drawline 是否画干扰线
     * @return
     */
    public BufferedImage generatorRotateVCodeImage(String vcode, boolean drawline){
        //创建验证码图片
        BufferedImage rotateVcodeImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2d = rotateVcodeImage.createGraphics();
        //填充背景色
        g2d.setColor(new Color(246, 240, 250));
        g2d.fillRect(0, 0, width, height);
        if(drawline){
            drawDisturbLine(g2d);
        }
        //在图片上画验证码
        for(int i = 0;i < vcode.length();i++){
            BufferedImage rotateImage = getRotateImage(vcode.charAt(i));
            g2d.drawImage(rotateImage, null, (int) (this.height * 0.7) * i, 0);
        }
        g2d.dispose();
        return rotateVcodeImage;
    }
    /**
     * 生成验证码
     * @return 验证码
     */
    public String generatorVCode(){
        int len = code.length;
        Random ran = new Random();
        StringBuffer sb = new StringBuffer();
        for(int i = 0;i < vcodeLen;i++){
            int index = ran.nextInt(len);
            sb.append(code[index]);
        }
        return sb.toString();
    }
    /**
     * 为验证码图片画一些干扰线
     * @param g 
     */
    private void drawDisturbLine(Graphics g){
        Random ran = new Random();
        for(int i = 0;i < disturbline;i++){
            int x1 = ran.nextInt(width);
            int y1 = ran.nextInt(height);
            int x2 = ran.nextInt(width);
            int y2 = ran.nextInt(height);
            g.setColor(getRandomColor());
            //画干扰线
            g.drawLine(x1, y1, x2, y2);
        }
    }
    /**
     * 获取一张旋转的图片
     * @param c 要画的字符
     * @return
     */
    private BufferedImage getRotateImage(char c){
        BufferedImage rotateImage = new BufferedImage(height, height, BufferedImage.TYPE_INT_ARGB);
        Graphics2D g2d = rotateImage.createGraphics();
        //设置透明度为0
        g2d.setColor(new Color(255, 255, 255, 0));
        g2d.fillRect(0, 0, height, height);
        Random ran = new Random();
        g2d.setFont(new Font(fontNames[ran.nextInt(fontNames.length)], fontStyles[ran.nextInt(fontStyles.length)], fontsize));
        g2d.setColor(getRandomColor());
        double theta = getTheta();
        //旋转图片
        g2d.rotate(theta, height/2, height/2);
        g2d.drawString(Character.toString(c), (height-fontsize)/2, fontsize+5);
        g2d.dispose();
        
        return rotateImage;
    }
    /**
     * @return 返回一个随机颜色
     */
    private Color getRandomColor(){
        Random ran = new Random();
        return new Color(ran.nextInt(220), ran.nextInt(220), ran.nextInt(220)); 
    }
    /**
     * @return 角度
     */
    private double getTheta(){
        return ((int) (Math.random()*1000) % 2 == 0 ? -1 : 1)*Math.random();
    }

    /**
     * @return 验证码字符个数
     */
    public int getVcodeLen() {
        return vcodeLen;
    }
    /**
     * 设置验证码字符个数
     * @param vcodeLen
     */
    public void setVcodeLen(int vcodeLen) {
        this.width = (fontsize+3)*vcodeLen+10;
        this.vcodeLen = vcodeLen;
    }
    /**
     * @return 字体大小
     */
    public int getFontsize() {
        return fontsize;
    }
    /**
     * 设置字体大小
     * @param fontsize
     */
    public void setFontsize(int fontsize) {
        this.width = (fontsize+3)*vcodeLen+10;
        this.height = fontsize+15;
        this.fontsize = fontsize;
    }
    /**
     * @return 图片宽度
     */
    public int getWidth() {
        return width;
    }
    /**
     * 设置图片宽度
     * @param width
     */
    public void setWidth(int width) {
        this.width = width;
    }
    /**
     * @return 图片高度
     */
    public int getHeight() {
        return height;
    }
    /**
     * 设置图片高度
     * @param height 
     */
    public void setHeight(int height) {
        this.height = height;
    }
    /**
     * @return 干扰线条数
     */
    public int getDisturbline() {
        return disturbline;
    }
    /**
     * 设置干扰线条数
     * @param disturbline
     */
    public void setDisturbline(int disturbline) {
        this.disturbline = disturbline;
    }
    
}

使用：

package com.servlet;


import java.awt.image.BufferedImage;
import java.io.IOException;

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

import com.tools.VCodeGenerator;
import com.tools.VcodeHelper;


public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        getVCode(req, resp);
    }
    private void getVCode(HttpServletRequest request, HttpServletResponse response) throws IOException {
        //创建验证码生成器对象
        VCodeGenerator vcGenerator = new VCodeGenerator();
        //生成验证码
        String vcode = vcGenerator.generatorVCode();
        //将验证码保存在session域中,以便判断验证码是否正确
        request.getSession().setAttribute("vcode", vcode);
        //生成验证码图片，两个方法选喜欢的用
        BufferedImage vImg = vcGenerator.generatorRotateVCodeImage(vcode, true);
        //BufferedImage vImg = vcGenerator.generatorVCodeImage(vcode, true);
        //输出图像
        ImageIO.write(vImg, "gif", response.getOutputStream());
        
        
    
    }
}

jsp页面：

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>验证码</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="Content-Type" content="text/html;charset=utf-8">
    <script type="text/javascript" src="js/jquery.min.js"></script>
    <script type="text/javascript">
      $(function(){
         $("#vcodeImg").click(function(){
             this.src="LoginServlet?method=GetVCode&t="+new Date().getTime();
         });
      });
    </script>
  </head>
  
  <body>
     <img title="点击图片切换验证码" id="vcodeImg" src="LoginServlet?method=GetVCode" >
   
  </body>
</html>