java生成验证码

都是基础知识,就不说废话了,直接上例子.

大家都能看懂的.

package com.gys;

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

import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class MakeCode {
    private Random random = new Random();
    private String randString = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";//随机产生的字符串
    
    private int width = 80;//图片宽
    private int height = 26;//图片高
    private int lineSize = 40;//干扰线数量
    private int stringNum = 4;//随机产生字符数量
    /*
     * 获得字体
     */
    private Font getFont(){
        return new Font("Fixedsys",Font.CENTER_BASELINE,18);
    }
    /*
     * 获得颜色
     */
    private Color getRandColor(int fc,int bc){
        if(fc > 255)
            fc = 255;
        if(bc > 255)
            bc = 255;
        int r = fc + random.nextInt(bc-fc-16);
        int g = fc + random.nextInt(bc-fc-14);
        int b = fc + random.nextInt(bc-fc-18);
        return new Color(r,g,b);
    }
    /**
     * 生成随机图片
     */
    public void getRandcode(HttpServletRequest request,
            HttpServletResponse response) {
        HttpSession session = request.getSession();
        //BufferedImage类是具有缓冲区的Image类,Image类是用于描述图像信息的类
        BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_BGR);
        Graphics g = image.getGraphics();//产生Image对象的Graphics对象,该对象可以在图像上进行各种绘制操作
        g.fillRect(0, 0, width, height);
        g.setFont(new Font("Times New Roman",Font.ROMAN_BASELINE,18));
        g.setColor(getRandColor(110, 133));
        //绘制干扰线
        for(int i=0;i<=lineSize;i++){
            drowLine(g);
        }
        //绘制随机字符
        String randomString = "";
        for(int i=1;i<=stringNum;i++){
            randomString=drowString(g,randomString,i);
        }
        session.removeAttribute("code");
        session.setAttribute("code", randomString);
        System.out.println(randomString);
        g.dispose();
        try {
            ImageIO.write(image, "JPEG", response.getOutputStream());//将内存中的图片通过流动形式输出到客户端
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    /*
     * 绘制字符串
     */
    private String drowString(Graphics g,String randomString,int i){
        g.setFont(getFont());
        g.setColor(new Color(random.nextInt(101),random.nextInt(111),random.nextInt(121)));
        String rand = String.valueOf(getRandomString(random.nextInt(randString.length())));
        randomString +=rand;
        g.translate(random.nextInt(3), random.nextInt(3));
        g.drawString(rand, 13*i, 16);
        return randomString;
    }
    /*
     * 绘制干扰线
     */
    private void drowLine(Graphics g){
        int x = random.nextInt(width);
        int y = random.nextInt(height);
        int xl = random.nextInt(13);
        int yl = random.nextInt(15);
        g.drawLine(x, y, x+xl, y+yl);
    }
    /*
     * 获取随机的字符
     */
    public String getRandomString(int num){
        return String.valueOf(randString.charAt(num));
    }
}

package com.gys;

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 GetCodeServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

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

        response.setContentType("image/jpeg");//设置相应类型,告诉浏览器输出的内容为图片
        response.setHeader("Pragma", "No-cache");//设置响应头信息，告诉浏览器不要缓存此内容
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expire", 0);
        MakeCode makeCode = new MakeCode();
        try {
            makeCode.getRandcode(request, response);//输出图片方法
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

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

}

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee                                                
    http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
    <servlet>
        <servlet-name>GetCodeServlet</servlet-name>
        <servlet-class>com.gys.GetCodeServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>GetCodeServlet</servlet-name>
        <url-pattern>/getCode</url-pattern>
    </servlet-mapping>
    
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
</web-app>

index.jsp:

<%@ 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>
     <script type="text/javascript">
        function getCode(obj) {
            obj.src = "getCode?"+Math.random();//防止出现缓存
        }
    </script>
  </head>
  
  <body>
        <img title="点击更换" onclick="getCode(this);" src="getCode"><br/>
  </body>
</html>

跑起来: