在servlet中生成验证码图片（二）

在原有生成验证码的功能基础上进行优化、修改，得此代码。该版本可以配置部分参数，如输出图片的类型、生成验证码使用的字符字典、在session中存取时使用的KEY等。如果您想了解旧代码，请参考：在servlet中生成验证码图片（http://blog.youkuaiyun.com/binbinxyz/article/details/18108271）。

package org.hbin.demo;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
import java.util.regex.Pattern;

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

import org.apache.log4j.Logger;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

/**
 * 

 * 验证码图片
 * 
 * 

 * 生成验证码图片。可以配置字符字典、在session中存取验证码时使用的KEY、输出图片的类型三个参数。其中输出图片类型支持GIF/gif、JPG/jpg、PNG/png三种格式，默认PNG/png格式。
 * 
 * 

 * 使用该类时，你可以参考如下方式在web.xml文件中配置Servlet：
 * 
 * <servlet>
 * 	<servlet-name>SimpleCaptchaServlet</servlet-name>
 * 	<servlet-class>org.hbin.demo.SimpleCaptchaServlet</servlet-class>
 * 	<init-param>
 * 		<param-name>map</param-name>
 * 		<param-value>ABCDEFghijkl</param-value>
 * 	</init-param>
 * 	<init-param>
 * 		<param-name>key</param-name>
 * 		<param-value>checkcode</param-value>
 * 	</init-param>
 * 	<init-param>
 * 		<param-name>imageType</param-name>
 * 		<param-value>JPG</param-value>
 * 	</init-param>
 * </servlet>
 * 
 * <servlet-mapping>
 * 	<servlet-name>SimpleCaptchaServlet</servlet-name>
 * 	<url-pattern>captcha.image</url-pattern>
 * </servlet-mapping>
 * 

* 在你的html/jsp页面中，你可以这样写：
*

<img alt="看不清楚?点击刷新" src="captcha.image" onclick="" style="cursor: pointer;"/>

*

* @file org/hbin/demo/CheckcodeImageServlet.java * @author hbin (cn.binbin@qq.com) * @version 2.0 * @date 2014/01/12 */ public class SimpleCaptchaServlet extends HttpServlet { private static final long serialVersionUID = 1110943583459995271L; protected static final String PNG = "image/png"; protected static final String JPG = "image/jpeg"; protected static final String GIF = "image/gif"; /** * 默认字符字典。
* 删除了人眼不易识别的数字0、1以及字母i、I、l、L、o、O */ protected static final String DEFAULT_MAP = "23456789abcdefghjkmnpqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ"; /** * 默认的HTTP Content-Type */ protected static final String DEFAULT_CONTENT_TYPE = PNG; /** * 在session中存取验证码时默认使用的KEY */ protected static final String DEFAULT_KEY = "captcha"; /** * 验证码的默认长度 */ protected static final int LENGTH = 4; /** * 图片默认宽度 */ protected static final int WIDTH = 100; /** * 图片默认高度 */ protected static final int HEIGHT = 30; /** * 随机数生成器 */ protected final Random r = new Random(); /** * Log4j's Logger instance. */ protected static Logger log = Logger.getLogger(SimpleCaptchaServlet.class); /** *

* 字符字典。
*

* 最小长度是3。可以包含大小写字母及数字。 */ protected String map; /** * 在session中存取验证码时使用的KEY */ protected String key; /** *

* 输出图片的类型
*

* 支持GIF/gif、JPG/jpg、PNG/png三种格式，默认PNG/png格式。 */ protected String imageType; /** * HTTP Content-Type */ protected String contentType; /** * 随机生成一种颜色 * * @return 生成的颜色 */ protected Color generateRandomColor() { return new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255)); } /** * 根据指定字符字典，生成指定长度的随机字符串 * * @param map * 指定的字符字典 * @param length * 指定的长度 * @return 指定长度的随机字符串 */ protected String generateRandomString(String map, int length) { StringBuffer b = new StringBuffer(); for (int i = 0; i < length; i++) { b.append(map.charAt(r.nextInt(map.length()))); } log.info("Generate a Image: length=" + length + ", string=" + b.toString()); return b.toString(); } /** * Initialize this servlet. * * @throws ServletException */ public void init() throws ServletException { String value = null; value = getServletConfig().getInitParameter("map"); if (value != null && Pattern.matches("[a-zA-Z0-9]{3,}", value)) { map = value; log.info("Initializing map with config value: " + map); } else { map = DEFAULT_MAP; log.info("Initializing map with default value: " + map); } value = getServletConfig().getInitParameter("key"); if (value != null) { key = value; log.info("Initializing key with config value: " + key); } else { key = DEFAULT_KEY; log.info("Initializing key with default value: " + key); } value = getServletConfig().getInitParameter("imageType"); if (value != null && value.toLowerCase().matches("(gif)|(jpg)|(png)")) { value = value.toLowerCase(); if ("gif".equals(value)) { contentType = GIF; } else if ("jpg".equals(contentType)) { contentType = JPG; } else { contentType = PNG; } log.info("Initializing contentType with config value: " + contentType); } else { contentType = DEFAULT_CONTENT_TYPE; log.info("Initializing contentType with default value: " + contentType); } } /** * Process an HTTP "GET" request. * * @param req * @param resp * @throws ServletException * @throws IOException */ public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doPost(req, resp); } /** * Process an HTTP "POST" request. * * @param req * @param resp * @throws ServletException * @throws IOException */ public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // 设置响应类型为图片 resp.setContentType(contentType); // 把页面设置为不缓存，禁止浏览器缓存该验证码图像 resp.setHeader("Pragma", "No-cache"); resp.setHeader("Cache-Control", "no-cache"); resp.setDateHeader("Expires", 0); log.info("Generate an Image: begin ..."); // 生成4位长度的验证码 String captcha = generateRandomString(map, LENGTH); // 将生成的验证码字符转换成小写并存入session req.getSession(true).setAttribute(key, captcha.toLowerCase()); log.info("Generate an Image: a String (value:" + captcha.toLowerCase() + ") is stored into session with key '" + key + "'."); // 在内存中创建图象 BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB); // 创建该图片的绘图对象 Graphics2D g = image.createGraphics(); // 创建一个较浅的颜色作为背景色 Color c = new Color(Integer.parseInt("E6E6E6", 16)); g.setColor(c); // 填充背景色 g.fillRect(0, 0, WIDTH, HEIGHT); // 创建一个颜色作为边框颜色 c = new Color(Integer.parseInt("A4A4A4", 16)); g.setColor(c); // 画边框 g.drawRect(0, 0, WIDTH - 1, HEIGHT - 1); // 随机干扰 for (int i = 0; i < 6; i++) { g.setColor(generateRandomColor()); g.drawLine(r.nextInt(WIDTH), r.nextInt(HEIGHT), r.nextInt(WIDTH), r.nextInt(HEIGHT)); } // 设置字体 Font font = new Font("Times New Roman", Font.BOLD, 20); g.setFont(font); // 将验证码字符绘到图象中 for (int i = 0; i < 4; i++) { g.setColor(generateRandomColor()); String s = Character.toString(captcha.charAt(i)); g.drawString(s, 20 * i + 10, HEIGHT - 6); } log.info("Generate an Image: write data to Stream ..."); // 获取页面输出流 ServletOutputStream out = resp.getOutputStream(); // 输出图像 // ImageIO.write(image, "jpeg", out); // 输出图像（该方式比上面的ImageIO更加高效） JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out); encoder.encode(image); // 刷新 out.flush(); log.info("Generate an Image: completed."); } }