Day 12 绝对路径相对路径

来源：互联网发布：tomcat修改端口号编辑：程序博客网时间：2024/06/04 23:29

一.绝对路径相对路径

1.开发时一般用绝对路径，写绝对路径可定不会出现问题，写相对路径有可能会出现问题

再由Servlet转发到JSP页面是，此时浏览器上显示的是Servlet的路径，而JSP页面的超链接还是相对于该JSP页面的地址，则可能会出现路径混乱的问题

2.编写绝对路径可以避免上述问题

1）绝对路径：相对于当前WEB应用的根路径的路径（即所有路径都得加contextPath）

如/代表的是站点的根目录则在前面加contextPath就好(而contextPath可以由request或application的getContextPath（）方法来获取)

例如：<%a href="<=request.getContextPath()%/TestServlet">to b</a>

response.sendRedirect(request.getContextPath()+"/path/c.jsp")

http://localhost:8080/contextPath(当前WEB应用的上下文路径)/a.jsp ---是绝对路径

http://localhost:8080/a.jsp --------不是

2)JAVAWEB开发中的 “/” 到底代表什么

①当前WEB应用的根路径：http://localhost:8080/contextPath/

---若/需交由Servlet容器来处理---

---各种定制标签中的---

>请求转发时：request.getRequestDispatcher("/path/b.jsp").forward(request, response);

>Web.xml文件映射Servlet访问路径：

<servlet-mapping>

</servlet-name>TestServlet</servlet-name>

<servlet-pattern>TestServlet</servlet-pattern>

</servlet-maping>

②WEB站点的路径：http://localhost:8080/

----若/交由浏览器来处理--

>超链接：<a href="TestServlet">to b</a>

>表达式中的action：<form action="/login.jsp">

>请求重定向的时候：request.getRequestDispatcher("/path/b.jsp").forward(request, response)

3.例：

相对路径：

a.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body><h4>aaa</h4><a href="TestServlet">to b</a></body></html>

TestServlet.java

package com.atguigu.javaweb;import java.io.IOException;import java.util.Arrays;import java.util.List;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * Servlet implementation class TServlet */@WebServlet("/TServlet")public class TServlet extends HttpServlet {private static final long serialVersionUID = 1L;/** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubString name="aaaccbb";request.setAttribute("name", name);request.getRequestDispatcher("/path/b.jsp").forward(request, response);}}

path/b.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body><h4>bbb</h4><br>cities:<%= request.getAttribute("name") %><a href="c.jsp">to c </a></body> </html>

c.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body><h4>ccc</h4><a href="../a.jsp">to a </a></body></html>

当从a到b后再到c就出问题了

改为绝对路径：

a.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body><h4>aaa</h4><a href="<%= request.getContextPath() %>/TestServlet">to b</a></body></html>

b.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body><h4>bbb</h4><br>cities:<%= request.getAttribute("name") %><a href="<%= request.getContextPath() %>/path/c.jsp">to c </a></body> </html>

c.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body><h4>ccc</h4><a href="<%= request.getContextPath() %>/a.jsp">to a </a></body></html>

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