最近对于request中的几种“路径”有点混淆，查找网上资源都没有很好的总结，希望此文章能够帮助我理解一下这几种“路径”。
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本文章主要讨论以下几种request获取路径的方法：
request.getServletPath()
request.getPathInfo()
request.getContextPath()
request.getRequestURI()
request.getRequestURL()
request.getServletContext().getRealPath()
以一个简单的例子说明：
web.xml配置（注意此处的url-pattern项）
<?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_2_5.xsd" id="WebApp_ID" version="2.5">
<display-name>aab</display-name>
<welcome-file-list>
<welcome-file>a.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>test</servlet-name>
<servlet-class>com.java.test.TestServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>test</servlet-name>
<url-pattern>/*</url-pattern><!-- 注意此处 -->
</servlet-mapping>
</web-app>
TestServlet.java文件：
package com.java.test;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class TestServlet extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("servletPath:"+req.getServletPath());
System.out.println("contextPath:"+req.getContextPath());
System.out.println("contextPath2:"+req.getServletContext().getContextPath());
System.out.println("pageInfo:"+req.getPathInfo());
System.out.println("uri:"+req.getRequestURI());
System.out.println("url:"+req.getRequestURL());
System.out.println("realPath:"+req.getServletContext().getRealPath("/"));
}
}
此时请求http://localhost:8080/testweb (url-pattern=/*)
打印出来的值为：
servletPath:
contextPath:/testweb
contextPath2:/testweb
pageInfo:null
uri:/testweb
url:http://localhost:8080/testweb
realPath:G:\java.metadata.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\testweb\
请求http://localhost:8080/testweb/abc 打印的值为：
servletPath:
contextPath:/testweb
contextPath2:/testweb
pageInfo:/abc
uri:/testweb/abc
url:http://localhost:8080/testweb/abc
realPath:G:\java.metadata.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\testweb\
当我们修改web.xml为如下时（注意url-pattern的改变）：
<?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_2_5.xsd" id="WebApp_ID" version="2.5">
<display-name>aab</display-name>
<welcome-file-list>
<welcome-file>a.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>test</servlet-name>
<servlet-class>com.java.test.TestServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>test</servlet-name>
<url-pattern>/abc/def/*</url-pattern><!-- 注意此处 -->
</servlet-mapping>
</web-app>
请求http://localhost:8080/testweb/abc/def/ghi/test.html (url-pattern=/abc/def/*)
打印的值为：
servletPath:/abc/def
contextPath:/testweb
contextPath2:/testweb
pageInfo:/ghi/test.html
uri:/testweb/abc/def/ghi/test.html
url:http://localhost:8080/testweb/abc/def/ghi/test.html
realPath:G:\java.metadata.plugins\org.eclipse.wst.server.core\tmp0\wtpwebapps\testweb\
通过观察打印结果，我们可以总结：
getServletPath():获取能够与“url-pattern”中匹配的路径，注意是完全匹配的部分，的部分不包括。
getPathInfo():与getServletPath()获取的路径互补，能够得到的是“url-pattern”中d的路径部分
getContextPath():获取项目的根路径
getRequestURI:获取根路径到地址结尾
getRequestURL:获取请求的地址链接（浏览器中输入的地址）
getServletContext().getRealPath("/"):获取“/”在机器中的实际地址
getScheme():获取的是使用的协议(http 或https)
getProtocol():获取的是协议的名称(HTTP/1.11)
getServerName():获取的是域名(xxx.com)
getLocalName:获取到的是IP
