使用Servlet绘制动态的数字图片

以下是web.xml的配置

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
	xmlns="http://java.sun.com/xml/ns/javaee" 
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <servlet>
    <servlet-name>GenerateImageServlet</servlet-name>
    <servlet-class>com.jadyer.servlet.GenerateImageServlet</servlet-class>
  </servlet>
  
  <servlet-mapping>
    <servlet-name>GenerateImageServlet</servlet-name>
    <url-pattern>/servlet/image</url-pattern>
  </servlet-mapping>
</web-app>

以下是index.jsp的内容

<%@ page language="java" pageEncoding="UTF-8"%>
<%response.sendRedirect(request.getContextPath()+"/servlet/image");%>

以下核心GenerateImageServlet.java的代码

package com.jadyer.servlet;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.imageio.stream.ImageOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 绘制随机数字图片的Servlet
 */
public class GenerateImageServlet extends HttpServlet {
	private static final long serialVersionUID = 760480418450678827L;
	
	// 产生的图像的宽度，单位为像素
	private final static int WIDTH = 260;
	
	// 产生的图像的高度，单位为像素
	private final static int HEIGHT = 60;
	
	public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
		// 设置输出的内容的类型为JPEG图像
		response.setContentType("image/jpeg");
		OutputStream os = response.getOutputStream();
		createImage(os);
		os.close();
	}
	
	/**
	 * 绘制输出整个图形
	 */
	public void createImage(OutputStream os) throws IOException {
		// 创建一个BufferedIamge对象
		BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
		
		// 获取的Graphics2D对象，通过这个对象完成绘图
		Graphics2D g = image.createGraphics();	
		
		// 绘制背景图
		g.setColor(Color.white);
		g.fillRect(0, 0, WIDTH, HEIGHT);	
		
		// 画边框
		g.setColor(Color.black);
		g.drawRect(0, 0, WIDTH - 1, HEIGHT - 1);
		
		// 设定字体
		g.setFont(new Font("Times New Roman", Font.PLAIN, 60));
		
		// 生成随机类
		Random random = new Random();
		
		// 取随机产生的6位数字
		for (int i = 0; i < 6; i++) {
			String rand = String.valueOf(random.nextInt(10));
			// 将随机产生的数字显示到图象中
			g.drawString(rand, 40 * i + 20, 50);
		}
		
		// 生成图像的输出流
		ImageOutputStream ios = ImageIO.createImageOutputStream(os);
		ImageIO.write(image, "jpeg", ios);
		ios.close();
	}
}