java web随机验证码生成，含改变颜色，字体，干扰线【完整过程附代码】

目标：要实现一个登陆界面，且含有验证码输入，输入验证码后可检验输入的正确性

jsp页面

登陆页面的前端login.jsp文件内容：

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>登陆页面</title>
</head>
<body>
 <script>
    function reloadCode(){
        var time=new Date().getTime();
        //由于传过去的时间不一样，所以不是同一个请求  同一个请求时不能实现更新
        document.getElementById("imageCode").src="<%=request.getContextPath()%>/servlet/CodeServlet?d="+time;
    }
    </script>
	<h1 style="align:center;margin:auto">  登陆界面 </h1>
	<div style = "margin:auto auto;width:320px;height:300px;margin-top:100px;
	position:'center';border:3px;border-color:blue;">
			<form action="/ex_7/servlet/ValidataServlet" method="post" style="margin:auto;width:250;height:82">
				账号：<input name = "account" type = "text"><br>
				密码：<input name = "password" type = "password"><br>
				<div>
				验证码：<input name="check_code" type = "text" width=60px height=20px value="验证码" />
				<img border=0 src="/ex_7/servlet/CodeServlet" id = "imageCode" onclick="reloadCode()" style="cursor:pointer;">
				</div>
				<input type = "submit" value ="登陆"  style="margin-left:100px;margin-top:10px;">
			</form>
	</div>
</body>
</html>

验证码生成

jsp页面对调用该CodeServlet.java的内容：
生成包含四个由数字：含大小写字母、随机字体和颜色、干扰线组成的一个验证码
各个板块在程序的注释中都有说明

package servlet;
import java.awt.*; //Graphics  Color    Font
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.*;

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;
import javax.servlet.http.HttpSession;

public class CodeServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
    private String[] fontNames = {"Georgia", "Verdana", "Arial", "Tahoma", 
    		"Time News Roman", "Courier New", "Arial Black", "Quantzite"};
  //内存中创建图像  设置图像个宽高
  	private int width = 60,height=20;
   
    public CodeServlet() {
        super();
        // TODO Auto-generated constructor stub
    }
    
    public String get_rand_digit_str() {
    	//取随机产生了的验证码（4位数字或字符）
    	Random rnd = new Random();
    	String str = "";
		int x = rnd.nextInt(2);
		if(x == 1) //大写字母
			str += (char) (65+rnd.nextInt(26)); //随机字符
		else if(x == 2) {  //小写字母
			str += (char) (97+rnd.nextInt(26));
		}
		else   //数字
			str+=String.valueOf(rnd.nextInt(9));  //随机一位数字
    	return str;
    }
    //获取  一种  随机颜色
    public Color rand_color() {
    	Random random = new Random();
        int r = random.nextInt(256);
        int g = random.nextInt(256);
        int b = random.nextInt(256);
        return new Color(r, g, b);
    }
    //获取    一种  字体 
    public Font rand_font() {
    	Random rnd = new Random();
    	int fontindex = rnd.nextInt(fontNames.length-1);  //随机索引
    	String str = fontNames[fontindex];  //获得该字体
        int fontSize = (int) Math.round(Math.random() * 4 + 16);  
    	return new Font(str, Font.PLAIN, fontSize);
    }
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setHeader("Cache-Control", "no-cache");
		
		BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
		//获取画笔
		Graphics g = image.getGraphics();
		//设定背景色
		g.setColor(new Color(200,200,200));
		g.fillRect(0, 0, width, height);  //设置背景板大小  并涂上颜色

		Random rnd = new Random();
		//画干扰线
		g.setColor(new Color(255,225,255));
    	//随机产生100个干扰线（点） ，使图像中验证码不易被其他程序探测到
		for(int i =0;i<80;i++) {
			int x =rnd.nextInt(width);
			int y = rnd.nextInt(height);
			int x1 = rnd.nextInt(2);  
            int y1 = rnd.nextInt(4); 
			g.drawOval(x,y,x+x1,y+y1);
		}
		
		//画一定个数的字符
		String randStr = "";
		for (int i = 0; i < 4; i++) {  
            String str = get_rand_digit_str();  //随机单个字符
            randStr += str;   //连接字符串
            g.setFont(rand_font());//随机字体  
            // 将认证码显示到图象中  
            g.setColor(rand_color());  
            g.drawString(str, 13 * i + 6, 16);  //i控制横坐标 将验证码显示到图像中
        }  
		//将验证码存入session
		HttpSession session = request.getSession();
		session.setAttribute("randStr",randStr);  //连接的字符串为验证码

		//输出图像到页面
		ImageIO.write(image,"JPG",response.getOutputStream());
	}
	
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

跳转检验

检验验证码输入是否正确，忽略大小写（validataServlet.java内容）：

package servlet;
import java.io.IOException;
import java.io.PrintWriter;

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

@WebServlet("/ValidataServlet")
public class ValidataServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
	}
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//得到提交的验证码
		String code = request.getParameter("check_code"); 
		//获取session中的验证码
		HttpSession session = request.getSession();
		String randStr = (String)session.getAttribute("randStr");
		response.setCharacterEncoding("gb2312");
		PrintWriter out = response.getWriter();
//		if(!code.equals(randStr)) {   //不能忽略大小写
		if(!code.equalsIgnoreCase(randStr)) {  //忽略大小写的字符串比较
			out.println("验证码错误");
		}
		else {
			out.println("验证码正确！跳转到LoginServlet.....");
		}
	}
}

xml文件配置

配置两个位于服务器端的servlet文件的路径：

  <servlet>
  <servlet-name>CodeServlet</servlet-name>
  <servlet-class>servlet.CodeServlet</servlet-class>
  </servlet>
  <servlet-mapping>
  	<servlet-name>CodeServlet</servlet-name>
    <url-pattern>/servlet/CodeServlet</url-pattern>
  </servlet-mapping>
  
  <servlet>
  <servlet-name>ValidataServlet</servlet-name>
  <servlet-class>servlet.ValidataServlet</servlet-class>
  </servlet>
  <servlet-mapping>
  	<servlet-name>ValidataServlet</servlet-name>
    <url-pattern>/servlet/ValidataServlet</url-pattern>
  </servlet-mapping>