通过listener理解域对象的生命周期

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REQUEST：

情况一：

e.jsp:

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>Title</title></head><body>   <form action="f.jsp" method="post">       name:<input type="text" name="name">       <input type="submit" value="submit">   </form></body></html>

f.jsp:

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>Title</title></head><body>   Hello:<%=request.getParameter("name")%></body></html>

测试:

进入e.jsp:

b表单提交后，进入f.jsp:

结论：
当一个响应返回时，即被销毁，当发送一个请求时被创建。而且f.jsp可以获取e.jsp传过来的name值。

情况二：

e.jsp:

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>Title</title></head><body>   <a href="f.jsp">to fff</a><%request.setAttribute("name","sasa");%></body></html>

f.jsp:

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>Title</title></head><body>   Hello:<%=request.getAttribute("name")%></body></html>

测试：

进入e.jsp:

通过超链接的方式进入f.jsp:

结论：通过超链接的方式进入f.jsp的话，f.jsp无法获取e.jsp页面request里面的属性。

情况三：

e.jsp:

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>Title</title></head><body><%request.setAttribute("name","sasa");%><jsp:forward page="f.jsp" ></jsp:forward></body></html>

f.jsp:

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>Title</title></head><body>   Hello:<%=request.getAttribute("name")%></body></html>

测试：

进入e.jsp后直接通过请求转发的方式进入f.jsp:

结论：请求转发只有一个request请求。
情况四：

TestServlet:

package com.sa.servlet;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(name = "TestServlet")public class TestServlet extends HttpServlet {    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {    }    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {         request.setAttribute("name","sasa");         request.getRequestDispatcher("/pages/f.jsp").forward(request,response);    }}

f.jsp:

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>Title</title></head><body>   Hello:<%=request.getAttribute("name")%></body></html>

测试：

情况五：

TestServlet:

package com.sa.servlet;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(name = "TestServlet")public class TestServlet extends HttpServlet {    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {    }    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {         request.setAttribute("name","sasa");         //request.getRequestDispatcher("/pages/f.jsp").forward(request,response);        response.sendRedirect(request.getContextPath()+"/pages/f.jsp");    }}

f.jsp:

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>Title</title></head><body>   Hello:<%=request.getAttribute("name")%></body></html>

测试：