Java Servlet 验证码生成与验证

代码都很简单，先看看效果，其它的直接看代码都会懂的：



验证码图片生成servlet：
总共就三步：
1)使用BufferedImage 创造一个图片
2)就是设置文字和一些干扰（颜色都是随机的）
  a) 设置背景色
  b) 随机画10条直线
  c) 生成4个随机的数字字母，这就是验证码
3)然后使用ImageIO写入到response的outputstream

就这么简单。

package com.luoyh.servlet;

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

import java.io.FileInputStream;
import java.net.URL;
import java.net.URLDecoder;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.awt.Graphics;
import java.util.Random;
import java.awt.Color;
import java.awt.Font;
/**
 * 创建随机图片验证码的servlet
 * 验证码存放在session当中
 * 在HandlerCode做验证处理
 * @see HandlerCode
 */
public class ValidateCode  extends HttpServlet {

        private static final long serialVersionUID = -1534235656L;

		private static final int[] FONT_STYLES = {Font.PLAIN, Font.ITALIC, Font.BOLD};
		// 0-9 a-z A-Z
		private static final int[] CHS = {48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 
			65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90,
			97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122};
		private static final int LINE_NUM = 10;
		// draw line numbers
		private static final int FONT_NUM = 3;

        protected void doGet(HttpServletRequest request,  HttpServletResponse response)  {
			try {
				// w: image width, h: image height, x: draw string begin x 
				int w = 150, h = 40, x = 20;
				// create code
				String code = "";
				BufferedImage newBi = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
				Graphics g = newBi.getGraphics();
				setColor(g);
				g.fillRect(0, 0, w, h);
				// rand draw line
				for(int i = 0; i < LINE_NUM; i ++) {
					setColor(g);
					g.drawLine(getRandom(w), getRandom(h), getRandom(w), getRandom(h));
				}
				// draw 4 character
				for(int i = 0; i < 4; i ++) {
					setColor(g);
					setFont(g);
					String ch = Character.toString((char)CHS[getRandom(62)]);
					code += ch;
					g.drawString(ch, x + getRandom(20), getRandom(h / 2) + 15 );
					x += 25;
				}
				// put code in session
				HttpSession session = request.getSession();
				session.setAttribute("code", code);
				System.out.println(code);
				// write image in response ouput stream
				ImageIO.write(newBi, "png", response.getOutputStream());
			} catch (Exception ex) {
				System.out.println("error");
			}
        }
		private void setFont(Graphics g) {
			g.setFont(new Font("Consolas", FONT_STYLES[getRandom(FONT_NUM)], 24));
		}
		private int getRandom(int rand) {
			return new Random().nextInt(rand);
		}
		private void setColor(Graphics g) {
			g.setColor(new Color(new Random().nextInt(0xffffff)));
		}

        protected void doPost(HttpServletRequest request,  HttpServletResponse response)  {
               doGet(request, response);
        }

		// test
		// use load image
		private FileInputStream readFile(String fileName) throws Exception {
			URL url = Thread.currentThread().getContextClassLoader().getResource("com/luoyh/servlet");

			String protocol = url.getProtocol(), code = url.getFile();
			//System.out.println("protocol: " + protocol + "code: " + code);
			String path = URLDecoder.decode(code, "utf-8");
			
			return new FileInputStream(path + "/" + fileName);
		}

}	

下面就是验证的servlet：

package com.luoyh.servlet;

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

import java.io.IOException;

/**
 * 验证码异步验证处理servlet
 **/ 
public class HandlerCode  extends HttpServlet {

		/**
		 * success return 0 else error.
		 *
		 */
        protected void doGet(HttpServletRequest request,  HttpServletResponse response) throws IOException  {
			try {
				String inputCode = request.getParameter("inputCode"),
					   sessionCode = (String) request.getSession().getAttribute("code");

				if(sessionCode == null || inputCode == null) {
					response.getWriter().write("-1");
					return;
				}
				// is equals
				if(inputCode.toUpperCase().equals(sessionCode.toUpperCase())) {
					response.getWriter().write("0");
				} else {
					response.getWriter().write("1");
				}
			} catch (Exception ex) {
				response.getWriter().write("-1");
			}
		}

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


}	

页面代码：

<%@ page contentType="text/html; charset=utf-8" pageEncoding="utf-8"%>
<%@ page trimDirectiveWhitespaces="true" %>
<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="utf-8" />
		<title>-DEMO-</title>

		<meta name="description" content="User login page" />
		<meta name="viewport" content="width=device-width, initial-scale=1.0" />
		<script type="text/javascript" src="jquery-2.1.0.min.js"></script>

	<style>
		a {
			text-decoration: none;
		}
	</style>
	  <script type="text/javascript">
		$(function(){

			// submit click handl
			$('#submit').click(function() { 
				$.ajax({
					url : '/demo/handler?inputCode=' + $('#code').val(),
					success: function(d) {
						if(d != '0') { // fail
							refresh();
						} else { // ok
							$('#code').attr('disabled', '');
							alert('Its ok!');
						}
						console.log(d);
					}
				});
			});
			// code refresh
			// set input disabled and empty 
			var refresh = function() {
				$('#code').removeAttr('disabled');
				$('#code').val('');
				$('#codeImg').attr('src', $('#codeImg').attr('_src') + '?t=' + new Date().getTime());
			};
			$('#refresh').click(function() {
				refresh();
			});
		});
	  </script>

	</head>

	<body>
		验证码：
		<input id="code" type="text" value="" />
		<a id="refresh" href="javascript:;">
			<img _src="<%=request.getContextPath()%>/validate" id="codeImg" src="<%=request.getContextPath()%>/validate" alt="" width="150" height="40" />
		</a>
		<br/>
		<input id="submit" type="button" value="确认" />  
		<hr>
	</body>
</html>

web.xml

	<servlet>
		<servlet-name>validate</servlet-name>
		<servlet-class>com.luoyh.servlet.ValidateCode</servlet-class>
	</servlet>

	<servlet-mapping>
		<servlet-name>validate</servlet-name>
		<url-pattern>/validate</url-pattern>
	</servlet-mapping>

	
	<servlet>
		<servlet-name>handler</servlet-name>
		<servlet-class>com.luoyh.servlet.HandlerCode</servlet-class>
	</servlet>

	<servlet-mapping>
		<servlet-name>handler</servlet-name>
		<url-pattern>/handler</url-pattern>
	</servlet-mapping>