1 package com; 2 3 import java.awt.Color; 4 import java.awt.Font; 5 import java.awt.Graphics2D; 6 import java.awt.image.BufferedImage; 7 import java.io.IOException; 8 import java.util.Random; 9 10 import javax.servlet.ServletException; 11 import javax.servlet.ServletOutputStream; 12 import javax.servlet.http.HttpServlet; 13 import javax.servlet.http.HttpServletRequest; 14 import javax.servlet.http.HttpServletResponse; 15 16 import com.sun.image.codec.jpeg.JPEGCodec; 17 import com.sun.image.codec.jpeg.JPEGImageEncoder; 18 19 public class IdentityServlet extends HttpServlet { 20 public static final char[] CHARS = { '2', '3', '4', '5', '6', '7', '8', 21 '9', '0', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 22 'L', 'M', 'N', 'O', 'P', 'K', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 23 'Y', 'Z' }; 24 25 public static Random random = new Random(); 26 27 public static String getRandomString() {// 随机获取6位 28 StringBuffer buffer = new StringBuffer(); 29 for (int i = 0; i < 6; i++) { 30 buffer.append(CHARS[random.nextInt(CHARS.length)]);// 随机获取一个字符 31 32 } 33 return buffer.toString(); 34 } 35 36 public static Color getRandomColor() { 37 return new Color(random.nextInt(255), random.nextInt(255), 38 random.nextInt(255)); 39 } 40 41 public static Color getReverseColor(Color c) {// 取反色 42 return new Color(255 - c.getRed(), 255 - c.getGreen(), 43 255 - c.getBlue()); 44 45 } 46 47 public void doGet(HttpServletRequest request, HttpServletResponse response) 48 throws ServletException, IOException { 49 response.setContentType("image/jpeg"); 50 String randomString = getRandomString(); 51 request.getSession(true).setAttribute("randomString", randomString); 52 int width = 100; 53 int height = 30; 54 Color color = getRandomColor(); 55 Color reverseColor = getReverseColor(color); 56 BufferedImage bImage = new BufferedImage(width, height, 57 BufferedImage.TYPE_INT_RGB); 58 Graphics2D graphics2d = bImage.createGraphics(); 59 graphics2d.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 16)); 60 graphics2d.setColor(color); 61 graphics2d.fillRect(0, 0, width, height); 62 graphics2d.setColor(reverseColor); 63 graphics2d.drawString(randomString, 18, 20); 64 for (int i = 0, n = random.nextInt(100); i < n; i++) { 65 graphics2d.drawRect(random.nextInt(width), random.nextInt(height), 66 1, 1); 67 68 } 69 ServletOutputStream outputStream = response.getOutputStream(); 70 JPEGImageEncoder coder = JPEGCodec.createJPEGEncoder(outputStream); 71 coder.encode(bImage); 72 outputStream.flush(); 73 } 74 75 }
需要注意的是在myEclipse中处理图片，需要引入两个包：
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
报错:
Access restriction: The type JPEGImageEncoder is not accessible due to
restriction on required library C:Javajre1.6.0_07lib
t.jar
此时解决办法：
MyEclipse默认把这些受访问限制的API设成了ERROR。只要把Windows-Preferences-Java-Complicer-Errors/Warnings里面的Deprecated
and restricted API中的Forbidden references(access rules)选为Warning就可以编译通过。
<%@ 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>My JSP 'index.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> </head> <body> <img src = "servlet/IdentityServlet" id = "identity" onload = "btn.disabled=false;"/> <input type = button value="next" onclick="reloadImage()" id = "btn"/> </body> <script> function reloadImage(){ document.getElementById('btn').disabled = true; document.getElementById('identity').src = 'servlet/IdentityServlet?ts='+new Date().getTime(); } </script> </html>
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0"> <display-name>servlet</display-name> <servlet> <description>This is the description of my J2EE component</description> <display-name>This is the display name of my J2EE component</display-name> <servlet-name>IdentityServlet</servlet-name> <servlet-class>com.IdentityServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>IdentityServlet</servlet-name> <url-pattern>/servlet/IdentityServlet</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.html</welcome-file> <welcome-file>index.htm</welcome-file> <welcome-file>index.jsp</welcome-file> <welcome-file>default.html</welcome-file> <welcome-file>default.htm</welcome-file> <welcome-file>default.jsp</welcome-file> </welcome-file-list> </web-app>