1. 概念:服务器端会话技术,在一次会话的多次请求间共享数据,将数据保存在服务器端的对象中。HttpSession
2. 快速入门:
1. 获取HttpSession对象:
HttpSession session = request.getSession();
2. 使用HttpSession对象:
Object getAttribute(String name)
void setAttribute(String name, Object value)
void removeAttribute(String name)
3. 原理
* Session的实现是依赖于Cookie的。
4. 细节:
1. 当客户端关闭后,服务器不关闭,两次获取session是否为同一个?
* 默认情况下。不是。
* 如果需要相同,则可以创建Cookie,键为JSESSIONID,设置最大存活时间,让cookie持久化保存。
Cookie c = new Cookie("JSESSIONID",session.getId());
c.setMaxAge(60*60);
response.addCookie(c);
2. 客户端不关闭,服务器关闭后,两次获取的session是同一个吗?
* 不是同一个,但是要确保数据不丢失。tomcat自动完成以下工作
* session的钝化:
* 在服务器正常关闭之前,将session对象系列化到硬盘上
* session的活化:
* 在服务器启动后,将session文件转化为内存中的session对象即可。
3. session什么时候被销毁?
1. 服务器关闭
2. session对象调用invalidate() 。
3. session默认失效时间 30分钟
选择性配置修改
<session-config>
<session-timeout>30</session-timeout>
</session-config>
5. session的特点
1. session用于存储一次会话的多次请求的数据,存在服务器端
2. session可以存储任意类型,任意大小的数据
* session与Cookie的区别:
1. session存储数据在服务器端,Cookie在客户端
2. session没有数据大小限制,Cookie有
3. session数据安全,Cookie相对于不安全
SessionDemo1.java 1. 使用session共享数据 2. 使用session获取数据 3. session对象持久化存储 4. 主动让session对象销毁
package Session;/*
*Created by tao on 2020-03-18.
*/
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import java.io.IOException;
@WebServlet("/sessionDemo1")
public class SessionDemo1 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
/*
* 一、使用session共享数据
* */
//1.获取session
HttpSession session1 = request.getSession();
//2.存储数据
session1.setAttribute("msg","hello session");
/*
*二、使用session获取数据
*/
//1.获取session
HttpSession session2 = request.getSession();
//2.获取数据
Object msg = session2.getAttribute("msg");
System.out.println(msg);
/*
*三、session对象持久化存储
* */
//1.获取session
HttpSession session3 = request.getSession();
System.out.println(session3);
//期望客户端关闭后,session也能相同
Cookie c = new Cookie("JSESSIONID",session3.getId());
c.setMaxAge(60*60);
response.addCookie(c);
/*
* 四、主动让session对象销毁
* */
HttpSession session4 = request.getSession();
session4.invalidate();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
session主要用于服务端之间多次请求的数据共享,使用时要注意session的存储方式和生命周期
1. login.jsp(简单的登录页面)
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>login</title>
<script>
window.onload = function () {
document.getElementById("img").onclick = function () {
this.src = "/checkCodeServlet1?time=" + new Date().getTime();
}
}
</script>
<style>
div {
color: red;
}
</style>
</head>
<body>
<form action="/loginServlet" method="post">
<table>
<tr>
<td>用户名</td>
<td><input type="text" name="username"></td>
</tr>
<tr>
<td>密码</td>
<td><input type="password" name="password"></td>
</tr>
<tr>
<td>验证码</td>
<td><input type="text" name="checkCode"></td>
</tr>
<tr>
<td colspan="2"><img id="img" src="/checkCodeServlet1"></td>
</tr>
<tr>
<td colspan="2"><input type="submit" value="登录"></td>
</tr>
</table>
</form>
<div><%=request.getAttribute("cc_error") == null ? "" : request.getAttribute("cc_error")%>
</div>
<div><%=request.getAttribute("login_error") == null ? "" : request.getAttribute("login_error") %>
</div>
</body>
</html>
2. success.jsp(成功登录后跳转的页面)
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<h2><%=request.getSession().getAttribute("user")%>,欢迎您</h2>
</body>
</html>
3. CheckCodeServlet.java(生成验证码图片的servlet,验证码会通过response的字节流方式输出到页面中,而正确的验证码字符会通过session做会话存储)
package Session;
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;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
@WebServlet("/checkCodeServlet1")
public class CheckCodeServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
int width = 100;
int height = 50;
//1.创建一对象,在内存中图片(验证码图片对象)
BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
//2.美化图片
//2.1 填充背景色
Graphics g = image.getGraphics();//画笔对象
g.setColor(Color.PINK);//设置画笔颜色
g.fillRect(0,0,width,height);
//2.2画边框
g.setColor(Color.BLUE);
g.drawRect(0,0,width - 1,height - 1);
String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
//生成随机角标
Random ran = new Random();
StringBuilder sb = new StringBuilder();
for (int i = 1; i <= 4; i++) {
int index = ran.nextInt(str.length());
//获取字符
char ch = str.charAt(index);//随机字符
sb.append(ch);
//2.3写验证码
g.drawString(ch+"",width/5*i,height/2);
}
String checkCode_session = sb.toString();
//将验证码存入session
request.getSession().setAttribute("checkCode_session",checkCode_session);
//2.4画干扰线
g.setColor(Color.GREEN);
//随机生成坐标点
for (int i = 0; i < 10; i++) {
int x1 = ran.nextInt(width);
int x2 = ran.nextInt(width);
int y1 = ran.nextInt(height);
int y2 = ran.nextInt(height);
g.drawLine(x1,y1,x2,y2);
}
//3.将图片输出到页面展示
ImageIO.write(image,"jpg",response.getOutputStream());
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
4. LoginServlet.java(接收前端登录发出的请求,然后根据判断做出相应的响应,如果登陆成功,重定向到success.jsp页面)
package Session;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
@WebServlet("/loginServlet")
public class
LoginServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.设置request编码
request.setCharacterEncoding("utf-8");
//2.获取参数
String username = request.getParameter("username");
String password = request.getParameter("password");
String checkCode = request.getParameter("checkCode");
//3.先获取生成的验证码
HttpSession session = request.getSession();
String checkCode_session = (String) session.getAttribute("checkCode_session");
//删除session中存储的验证码
session.removeAttribute("checkCode_session");
//3.先判断验证码是否正确
if(checkCode_session!= null && checkCode_session.equalsIgnoreCase(checkCode)){
//忽略大小写比较
//验证码正确
//判断用户名和密码是否一致
if("kt".equals(username) && "123".equals(password)){//需要调用UserDao查询数据库
//登录成功
//存储信息,用户信息
session.setAttribute("user",username);
//重定向到success.jsp
response.sendRedirect(request.getContextPath()+"/success.jsp");
}else{
//登录失败
//存储提示信息到request
request.setAttribute("login_error","用户名或密码错误");
//转发到登录页面
request.getRequestDispatcher("/login.jsp").forward(request,response);
}
}else{
//验证码不一致
//存储提示信息到request
request.setAttribute("cc_error","验证码错误");
//转发到登录页面
request.getRequestDispatcher("/login.jsp").forward(request,response);
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}