Java编写验证码

时间：2024-01-01 19:40:57

Java后台代码（CheckCodeServlet.java）

package web;

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.io.OutputStream;

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;

public class CheckCodeServlet extends HttpServlet {

    /*

     * 返回一张动态图片

     *

     */

    public void service(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/jpeg");

        //获取字节流

        OutputStream os=response.getOutputStream();

        //图片映射区，理解成画板就行，画验证码

    //    BufferedImage image=new BufferedImage(width,height,imageType);

        BufferedImage image=new BufferedImage(80,40,BufferedImage.TYPE_INT_RGB);

        //画笔

        Graphics g=image.getGraphics();

        //添加背景颜色（随机）

        Random r=new Random();

        g.setColor(new Color(r.nextInt(256),r.nextInt(256),r.nextInt(256)));//Color(red,green,blue);rgb格式的颜色设置

        g.fillRect(0, 0, 80, 40);//画矩形区域

        //画字符串

        g.setColor(Color.black);//设置验证码的颜色

        g.setFont(new Font(null,Font.BOLD,20));//设置验证码的字体 Font(字体,样式,大小)

        String num=getNum(5);//调入验证码

        g.drawString(num, 5, 30);//(字符串内容,X坐标,Y坐标)

        //划线，干扰机器人识别验证码

        for(int i=0;i<6;i++){

            //画6条线

            g.setColor(new Color(r.nextInt(256),r.nextInt(256),r.nextInt(256)));//设置线的颜色

            g.drawLine(r.nextInt(80),r.nextInt(80),r.nextInt(80),r.nextInt(80));//g.drawLine(起点X坐标,起点Y坐标,终点X坐标,终点Y坐标);

        }

        //压缩 传输（画出的图片比较大，需要压缩，画出的是24位图）

        ImageIO.write(image, "jpeg", os);

    }

    //返回正确的验证码

    //length：验证码的长度

    public String getNum(int length){

        String str="ABCDEFGHIJKLMNOPQRSTUVWXYZ123456789";//常量，为了根据长度挑出随机的验证码

        Random r=new Random();

        StringBuffer sf=new StringBuffer();

        for(int i=0;i<length;i++){

            int index=r.nextInt(str.length());//取str的下标

            char c=str.charAt(index);//根据下标取字符

            sf.append(c);//字符放入字符串缓冲区

        }

        return sf.toString();//转换成字符串返回

    }

}

web.xml配置文件

<servlet>

    <servlet-name>CheckCodeServlet</servlet-name>

    <servlet-class>web.CheckCodeServlet</servlet-class>

  </servlet>

  <servlet-mapping>

    <servlet-name>CheckCodeServlet</servlet-name>

    <url-pattern>/checkCode</url-pattern>

  </servlet-mapping>

text.jsp

<%@ page language="java" contentType="text/html; charset=utf-8"

    pageEncoding="utf-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=utf-8">

<title>Insert title here</title>

</head>

<body>

<input >

	图片：<img id="num" src="checkCode"><a href="javascript:;" onclick="document.getElementById('num').src='checkCode?'+new Date().getTime();">换一张</a>

</body>

</html>

　　

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