javaWEB总结(24):相对路径和绝对路径

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相对路径

项目结构1

web.xml

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">  <display-name>javaWeb_24</display-name>  <welcome-file-list>    <welcome-file>a.jsp</welcome-file>  </welcome-file-list></web-app>

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>A.jsp</title></head><body><!-- 相对路径，当前目录下的path下的b.jsp --><a href="./path/b.jsp">To B.jsp</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>B.jsp</title></head><body><!-- 相对路径，当前目录下的c.jsp --><a href="./c.jsp">To C.jsp</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>C.jsp</title></head><body><!-- 相对路径，上层目录下的b.jsp --><a href="../a.jsp">to A.jsp</a></body></html>

运行结果1

有时候我们需要显示一些数据，可能会通过转发的方式到另外一个页面。

项目结构2

web.xml

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">  <display-name>javaWeb_24</display-name>  <welcome-file-list>    <welcome-file>a.jsp</welcome-file>  </welcome-file-list></web-app>

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>A.jsp</title></head><body><a href="toBServlet">To B.jsp</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>B.jsp</title></head><body>cities:<%=request.getAttribute("cities") %><br><br><!-- 相对路径，当前目录下的c.jsp --><a href="./c.jsp">To C.jsp</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>C.jsp</title></head><body><!-- 相对路径，上层目录下的b.jsp --><a href="../a.jsp">to A.jsp</a></body></html>

ToBServlet.java

package com.dao.chu;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 ToBServlet */@WebServlet("/toBServlet")public class ToBServlet 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 {List<String> cities =Arrays.asList("北京","上海","广州","深圳");request.setAttribute("cities", cities);request.getRequestDispatcher("/path/b.jsp").forward(request, response);}}

运行结果2

点击 To B.jsp后，地址栏中http://localhost:8080/javaWeb_24/toBServlet 为跟路径下，所以点击To C.jsp会默认以跟路径为相对路径http://localhost:8080/javaWeb_24/c.jsp，这样便出现了问题。

绝对路径

javaWeb中什么是绝对路径?

相对于当前web应用的跟路径。此处为:http://localhost:8080/javaWeb_24/。即任何的路径都必须戴上contextPath.
注意:http://localhost:8080/此路径为WEB站点的跟路径。

如何完成编写?

若/代表的是当前WEB站点的跟路径，则在其前面加上contextPath就可以。
而contextpath可以由request或application的getContextPath()方法来获取。

javaweb开发中的"/“代表什么?

①当前WEB应用的跟路径:

1.请求转发时request.getRequestDispatcher("/path/b.jsp").forward(request, response);
2.web.xml文件中映射servlet访问路径
3.各种标签中的/

②WEB站点的跟路径:

1.超链接.

2.表单中的action.

3.请求重定向时，response.sendRedirect.

总结:若"/“需交由Servlet容器来处理，则代表当前WEB应用的跟路径。若"/”交由游览器来处理，则代表当前WEB站点的跟路径。

所以只需在三个超链接加上<%=request.getContextPath() %>即可。

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>A.jsp</title></head><body><a href="<%=request.getContextPath() %>/toBServlet">To B.jsp</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>B.jsp</title></head><body>cities:<%=request.getAttribute("cities") %><br><br><!-- 相对路径，当前目录下的c.jsp --><a href="<%=request.getContextPath() %>/path/c.jsp">To C.jsp</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>C.jsp</title></head><body><!-- 相对路径，上层目录下的b.jsp --><a href="<%=request.getContextPath() %>/a.jsp">to A.jsp</a></body></html>

修改后，运行结果正常

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