代码仓库:https://gitee.com/DerekAndroid/CookieSession.git
案例一:记录最后一次访问时间
若用户是第一次登录该网站
提示:欢迎访问
若用户不是第一次登录该网站
提示:您上次访问的时间为:xxxxxxxx
步骤分析:
1.获取所有的cookie数组
2.从数组中查找含有最后一次访问时间的cookie
3.若没有查到对应的cookie 那么说明是第一次访问该网站 提示:欢迎访问
4.若查到对应的cookie 说明 不是第一次访问该网站 获取当前cookie的value值 提示:您最后一次访问时间为value
5.获取当前的时间
6.把当前的事件放到cookie中
验证码生成+session保存:
package com.itheima.servlet;
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.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class CodeServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 使用java图形界面技术绘制一张图片
int charNum = 4;
int width = 20 * 4;
int height = 28;
// 1. 创建一张内存图片
BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
// 2.获得绘图对象
Graphics graphics = bufferedImage.getGraphics();
// 3、绘制背景颜色
graphics.setColor(Color.YELLOW);
graphics.fillRect(0, 0, width, height);
// 4、绘制图片边框
graphics.setColor(Color.GRAY);
graphics.drawRect(0, 0, width - 1, height - 1);
// 5、输出验证码内容
graphics.setColor(Color.RED);
graphics.setFont(new Font("宋体", Font.BOLD, 22));
// 随机输出4个字符
String s = "ABCDEFGHGKLMNPQRSTUVWXYZ23456789";
Random random = new Random();
// session中要用到
String msg = "";
int x = 5;
for (int i = 0; i < charNum; i++) {
int index = random.nextInt(32);
String content = String.valueOf(s.charAt(index));
msg += content;
graphics.setColor(new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255)));
graphics.drawString(content, x, 22);
x += 20;
}
request.getSession().setAttribute("sessionYzm", msg);
// 6、绘制干扰线
graphics.setColor(Color.GRAY);
for (int i = 0; i < 5; i++) {
int x1 = random.nextInt(width);
int x2 = random.nextInt(width);
int y1 = random.nextInt(height);
int y2 = random.nextInt(height);
graphics.drawLine(x1, y1, x2, y2);
}
// 释放资源
graphics.dispose();
// 图片输出 ImageIO
ImageIO.write(bufferedImage, "jpg", response.getOutputStream());
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}
登录校验验证码
package com.itheima.c_case;
import java.io.IOException;
import java.text.DateFormat;
import java.util.Date;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LastTimeServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//处理响应乱码
response.setContentType("text/html;charset=utf-8");
//获取所有的cookie数组
Cookie[] cookies = request.getCookies();
//从cookie数组中查找含有lastTime的cookie
Cookie co = null;
if(cookies!=null){
//查找cookie
for(Cookie cookie:cookies){
//哪个cookie含有lastTime
if("lastTime".equals(cookie.getName())){
co=cookie;
}
}
}
//判断是否存在cookie
if(co!=null){
response.getWriter().print("您上次的访问时间为:"+co.getValue());
}else{
response.getWriter().print("欢迎访问");
}
//获取当前的时间
DateFormat df = DateFormat.getDateTimeInstance();
String format = df.format(new Date());
//把当前时间放入cookie中
Cookie cookie = new Cookie("lastTime", format);
//设置cookie的存活时间
cookie.setMaxAge(3600);
//写回到浏览器
response.addCookie(cookie);
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
案例二:一次性验证码
需求:
把验证码添加到登录案例中
并且对验证码的输入进行校验
若验证码没有输入或者输入的为空格 提示:请输入验证码
若验证码输入了 但是输入的不正确 提示:请输入正确的验证码
步骤:
1.复制day1102项目
2.修改web action
3.//把msg放入session域对象中
4.servlet的操作
//获取前台录入的验证码
//若用户没有输入或者输入的为空格 提示:请输入验证码
//若用户输入值,但是值不正确
//判断前台录入的值和session中的验证码是否一致
package com.itheima.servlet;
import java.io.IOException;
import java.sql.SQLException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.itheima.bean.User;
import com.itheima.service.LoginService;
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setHeader("content-type", "text/html;charset=utf-8");
//获取请求的用户名和密码
String username = request.getParameter("username");
String password = request.getParameter("password");
System.out.println("username="+username);
//获取前台录入的验证码
String yzm = request.getParameter("yzm");
System.out.println("yzm="+yzm);
//从session中获取图片中的验证码
String sessionYzm=(String)request.getSession().getAttribute("sessionYzm");
System.out.println("sessionYzm="+sessionYzm);
//清空session 保证点击登录的时候 验证码是最新的
request.getSession().removeAttribute("sessionYzm");
//创建LoginService
LoginService ls = new LoginService();
try {
//校验验证码
if(yzm==""||yzm.trim().length()==0){
//把错误信息放入request域中
request.setAttribute("msg", "请输入验证码");
//请求转发
request.getRequestDispatcher("/login.jsp").forward(request, response);
//直接返回,后续的不执行,不然会报错: Cannot forward after response has been committed
return;
}else{
//如果两个验证不一样 需要给出提示
if(!yzm.equalsIgnoreCase(sessionYzm)){
System.out.println("请输入正确的验证码");
//把错误信息放入request域中
request.setAttribute("msg", "请输入正确的验证码");
//请求转发
request.getRequestDispatcher("/login.jsp").forward(request, response);
return;
}
}
//调用service中的方法
User user=ls.getUserByUsernameAndPwd(username,password);
//根据返回的对象,判断提示信息的内容
System.out.println(request.getContextPath());
if(user==null){
//response.getWriter().println("登录失败");
//把错误信息放入request域对象中
request.setAttribute("msg", "登录失败");
//使用请求转发跳转到login.jsp
request.getRequestDispatcher("/login.jsp").forward(request, response);
return;
//不能使用重定向,因为使用重定向后request失效
//response.sendRedirect("/day1102/login.jsp");
}else{
request.getSession().setAttribute("username", user.getUsername());
response.getWriter().println(user.getUsername()+":欢迎回来");
request.getRequestDispatcher("/1.jsp").forward(request, response);
System.out.println("/1.jsp");
return;
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}