标签：http JavaWeb 作用域 Servlet req import servlet javax
保存作用域
page-页面级别（已过时）
request-一次请求响应范围
准备两个demo
package com.fancy.demo;
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.io.IOException;
/**
* @Name demo02
* @Description 演示request保存作用域
* @Author Fancy
* @return 2022/8/3
* @Version 1.0
*/
@WebServlet("/demo02")
public class Demo02Servlet extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取request保存作用域保存的数据，key为uname
Object unameObj = req.getAttribute("uname");
System.out.println("unameObj =" + unameObj);
}
}package com.fancy.demo;
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.io.IOException;
/**
* @Name demo01
* @Description request保存作用域
* @Author Fancy
* @return 2022/8/3
* @Version 1.0
*/
@WebServlet("/demo01")
public class Demo01Servlet extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//1.向request保存作用域保存数据
req.setAttribute("uname","keke");
//2.客户端重定向
resp.sendRedirect("demo02");
}
}使用客户端重定向，客户端获取不到value的值keke
接下来使用服务器内部转发
更改demo02代码
package com.fancy.demo;
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.io.IOException;
/**
* @Name demo01
* @Description request保存作用域
* @Author Fancy
* @return 2022/8/3
* @Version 1.0
*/
@WebServlet("/demo01")
public class Demo01Servlet extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//1.向request保存作用域保存数据
req.setAttribute("uname","keke");
/* //2.客户端重定向
resp.sendRedirect("demo02");*/
//服务器内部转发
req.getRequestDispatcher("demo02").forward(req,resp);
}
}
获取成功
session-一次会话范围
准备两个demo
package com.fancy.demo;
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.io.IOException;
/**
* @Name demo03
* @Description session保存作用域
* @Author Fancy
* @return 2022/8/3
* @Version 1.0
*/
@WebServlet("/demo03")
public class Demo03Servlet extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//1.想request保存作用域保存数据
req.getSession().setAttribute("uname","keke");
/* //2.客户端重定向
resp.sendRedirect("demo02");*/
//服务器内部转发
req.getRequestDispatcher("demo04").forward(req,resp);
}
}package com.fancy.demo;
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.io.IOException;
@WebServlet("/demo04")
public class Demo04Servlet extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取session保存作用域保存的数据，key为uname
Object unameObj = req.getSession().getAttribute("uname");
System.out.println("unameObj =" + unameObj);
}
}从session中也可以成功获取value值
application-一次应用程序范围有效
package com.fancy.demo;
import javax.servlet.ServletContext;
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.io.IOException;
/**
* @Name demo05
* @Description application保存作用域
* @Author Fancy
* @return 2022/8/3
* @Version 1.0
*/
@WebServlet("/demo05")
public class Demo05Servlet extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//1.想request保存作用域保存数据
//Servlet上下文
ServletContext application = req.getServletContext();
application.setAttribute("uname","keke");
//2.客户端重定向
resp.sendRedirect("demo06");
/*//服务器内部转发
req.getRequestDispatcher("demo06").forward(req,resp);*/
}
}package com.fancy.demo;
import javax.servlet.ServletContext;
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.io.IOException;
/**
* @Name demo06
* @Description application保存作用域
* @Author Fancy
* @return 2022/8/3
* @Version 1.0
*/
@WebServlet("/demo06")
public class Demo06Servlet extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//获取application保存作用域保存的数据，key为uname
ServletContext application = req.getServletContext();
Object unameObj = application.getAttribute("uname");
System.out.println("unameObj =" + unameObj);
}
}可获取到value值
并且使用其它浏览器访问application作用域也可以得到value值（Tomcat未停止）
标签：http,JavaWeb,作用域,Servlet,req,import,servlet,javax 来源： https://www.cnblogs.com/fancy2022/p/16549148.html
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