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JAVASession

IT知识sessionJavaSe

书到用时方恨少，事非经过不知难。这篇文章主要讲述JAVASession相关的知识，希望能为你提供帮助。
Session

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。

示例代码，两个servlet之间，一个填写Session，另一个获得Session
以下是用于获得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("/sessionDemo1")
public class SessionDemo1 extends HttpServlet
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
//使用session共享数据

//1.获取session
HttpSession session = request.getSession();
//2.存储数据
session.setAttribute("msg","hello session");


protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
this.doPost(request, response);


【JAVASession】另一个是用于打印session里的数据
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("/sessionDemo2")
public class SessionDemo2 extends HttpServlet
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
//使用session获取数据

//1.获取session
HttpSession session = request.getSession();
//2.获取数据
Object msg = session.getAttribute("msg");
System.out.println(msg);


protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
this.doPost(request, response);


Session的注意事项
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);

示例代码
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import java.io.IOException;

@WebServlet("/sessionDemo3")
public class SessionDemo3 extends HttpServlet
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException

//1.获取session
HttpSession session = request.getSession();
System.out.println(session);

//期望客户端关闭后，session也能相同
Cookie c = new Cookie("JSESSIONID",session.getId());
c.setMaxAge(60*60);
response.addCookie(c);



protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
this.doPost(request, response);


另一个servlet用于查看，验证是否关闭客户端也是获得同一个session
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import java.io.IOException;

@WebServlet("/sessionDemo4")
public class SessionDemo4 extends HttpServlet
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException

//1.获取session
HttpSession session = request.getSession();
System.out.println(session);



protected void

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