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,width,height);
		
		///画边框
		graphics.setColor(Color.blue);
		graphics.drawRect(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,IOException {
		// TODO Auto-generated method stub
	}

}