进行一次性校验码的校验（session、时间戳、随机数、字符缓存、绘画）

	

		姓名  密码 
		

			验证码
		
		

			
		
		
		
	

package javapack;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class checkimagservlet extends HttpServlet {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		int width=120;
		int height=30;
		//步骤一 绘制一张内存中的图片
		BufferedImage bi=new BufferedImage (width,height,BufferedImage.TYPE_INT_RGB);//表示一个图像，该图像具有整数像素的 8 位 RGB 颜色
		//步骤二 图片绘制背景颜色 ---通过绘图对象
		Graphics g=bi.getGraphics();//得到画图对象---画笔
		//绘制任何图形之前，都必须指定一个颜色
		g.setColor(getRandColor(200,250));
		g.fillRect(0, 0, width, height);//画填充矩形,前两个参数指的是矩形左上角的坐标，后两个参数是矩形的宽和高
		//步骤三 绘制边框
		g.setColor(Color.WHITE);
		g.drawRect(0, 0, width-1, height-1);
		//步骤四 四个随机数字
		Graphics2D g2=(Graphics2D) g;
		//设置输出字体
		g2.setFont(new Font("宋体",Font.BOLD,18));//参数为字体、风格、字号
		String words="ABCDEFGHIGKLMNOPQRSTUVWXYZ1234567890";
		Random random=new Random();//生成随机数
		//将生成的验证码保存到session中
		StringBuffer buffer=new StringBuffer();
		//定义X坐标
		int x=10;
		for(int i=0;i<4;i++){
			//随机颜色new corlor(r,g,b)
			g2.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//nextInt(n),生成一个0到n的数
			//旋转-30,---30度
			int jiaodu =random.nextInt(60)-30;
			//换算弧度
			double theta =jiaodu*Math.PI/180;
			//生成一个随机数字
			int index=random.nextInt(words.length());//从word中随便选取一个值
			//获得字母数字
			char c=words.charAt(index);
			//将生成的字加入到buffer中
			buffer.append(c);
			//将c输出到图片
			g2.rotate(theta, x, 20);
			g2.drawString(String.valueOf(c), x, 20);
			g2.rotate(-theta, x, 20);
			x+=30;
		}
		request.getSession().setAttribute("code", buffer.toString());
		//步骤五 绘制干扰线
		g.setColor(getRandColor(160,200));
		int x1;
		int x2;
		int y1;
		int y2;
		for(int i=0;i<30;i++){
			x1=random.nextInt(width);
			x2=random.nextInt(12);
			y1=random.nextInt(height);
			y2=random.nextInt(12);
			g.drawLine(x1, y1, x1+x2, y1+y2);
		}
		//将上面图片输出到浏览器
		g.dispose();//释放资源
		ImageIO.write(bi,"jpg",response.getOutputStream());
	}

	private Color getRandColor(int fc, int bc) {
		// TODO Auto-generated method stub
		Random random=new Random();
		if(fc>255){
			fc=255;
		}
		if(bc>255){
			bc=255;
		}
		int r=fc+random.nextInt(bc-fc);
		int g=fc+random.nextInt(bc-fc);
		int b=fc+random.nextInt(bc-fc);
		return new Color(r, g, b);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

}

package javapack;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.SQLException;

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

public class httpservlet extends HttpServlet {

	@Override
	public void init() throws ServletException {
		// TODO Auto-generated method stub
		//初始化一个变量count值为0，用来记录登录的人数
		int count=0;
		//将这个值存入servletcontext
		this.getServletContext().setAttribute("count", count);
	}
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html; charset=UTF-8");//解决向页面输出中文乱码,而且还可以写HTML
		final long serialVersionUID=1L;
		//校验验证码
		String code1 = request.getParameter("code");
		String code2 = (String) request.getSession().getAttribute("code");
		request.getSession().removeAttribute("code");//清除session
		if(!code1.equalsIgnoreCase(code2))//忽略大小写
		{
			request.setAttribute("msg", "验证码输入错误");
			request.getRequestDispatcher("/html/login.jsp").forward(request,response);
			return;
		}
		//接收表单参数
		String username=request.getParameter("username");//通过input的name值获得输入的username
		String password=request.getParameter("password");
		//封装到实体对象
		User user=new User();
		user.setUsername(username);//将username与password封装到user对象中
		user.setPassword(password);
		//调用业务层处理数据
		userservice us=new userservice();
		try {
			User existuser=us.login(user);//将user传入到login方法判断用户是否在数据库中存在
			//根据处理结果显示信息（页面跳转）
			if(existuser==null){
				response.getWriter().println("
登录失败
");
			}
			else{
				//记录登录成功的人数
				int count=(Integer) this.getServletContext().getAttribute("count");
				count++;
				this.getServletContext().setAttribute("count", count);
				/*response.getWriter().println("
登录成功，你好,"+existuser.getUsername()+"
");
				response.getWriter().println("
1s后页面跳转。。。。
");
				response.setHeader("Refresh","1;url=/J2EE/countservlet");*/
				/*response.setStatus(302);//状态码重定向
				response.setHeader("Location", "/J2EE/html/success.html");*/
				response.sendRedirect( "/J2EE/countservlet");
				return;
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		doGet(request, response);//post方式和get方式执行同一方法
	}

}