java web中图片验证码功能的简单实现方法

package com.lsgjzhuwei.servlet.response;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.IOException;import java.util.Random;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;/** * Servlet implementation class VerificationCode */@WebServlet(asyncSupported = true, urlPatterns = { "/VerificationCode" })public class VerificationCode extends HttpServlet {	private static final long serialVersionUID = 1L;      /**   * @see HttpServlet#HttpServlet()   */  public VerificationCode() {    super();    // TODO Auto-generated constructor stub  }	/**	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)	 */	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {		// TODO Auto-generated method stub				int width = 120;		int height = 30;				//创建一张内存中的缓存图片		BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);				///背景色		//通过graphics绘制图像		Graphics graphics = bufferedImage.getGraphics();		//设置颜色		graphics.setColor(Color.yellow);		//填充		graphics.fillRect(0, 0, width, height);				///画边框		graphics.setColor(Color.blue);		graphics.drawRect(0, 0, width-1, height-1);				//写字母		String content = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcedfghijklmnopqrstuvwxyz1234567890";		Random random = new Random();		//设置字体颜色		graphics.setColor(Color.red);		//设置字体及大小		graphics.setFont(new Font("宋体", Font.BOLD, 20));		int x=20;		int y=20;		for(int i = 0; i < 4; i++)		{			int index = random.nextInt(content.length());			char letter = content.charAt(index);			graphics.drawString(letter+" ", x, y);			x = x+20;		}				//绘制干扰线		int x1;		int x2;		int y1;		int y2;		graphics.setColor(Color.LIGHT_GRAY);		for(int i = 0;i <50;i++)		{			x1=random.nextInt(width);			x2=random.nextInt(width);			y1=random.nextInt(height);			y2=random.nextInt(height);			graphics.drawLine(x1, y1, x2, y2);		}				//将图片输出到浏览器		//将内存的图片通过浏览器输出流输出成jpg图片		ImageIO.write(bufferedImage, "jpg", response.getOutputStream());					}	/**	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)	 */	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {		// TODO Auto-generated method stub	}}