(轉)關於request.getServletPath()，request.getContextPath()的總結

文章徹底轉載自 : https://blog.csdn.net/qq_27770257/article/details/79438987

最近對於request中的幾種「路徑」有點混淆，查找網上資源都沒有很好的總結，但願此文章可以幫助我理解一下這幾種「路徑」。 
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本文章主要討論如下幾種request獲取路徑的方法：

request.getServletPath()
request.getPathInfo()
request.getContextPath()
request.getRequestURI()
request.getRequestURL()
request.getServletContext().getRealPath()

以一個簡單的例子說明： 
web.xml配置（注意此處的url-pattern項）

<?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><!-- 注意此處 -->
    </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("/"));

    }

}

此時請求http://localhost:8080/testweb (url-pattern=/*) 
打印出來的值爲：

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\

請求http://localhost:8080/testweb/abc 打印的值爲：

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\

當咱們修改web.xml爲以下時（注意url-pattern的改變）：

<?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><!-- 注意此處 -->
    </servlet-mapping>

</web-app>

請求http://localhost:8080/testweb/abc/def/ghi/test.html (url-pattern=/abc/def/*) 
打印的值爲：

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\

經過觀察打印結果，咱們能夠總結：
1. getServletPath():獲取可以與「url-pattern」中匹配的路徑，注意是徹底匹配的部分，*的部分不包括。
2. getPageInfo():與getServletPath()獲取的路徑互補，可以獲得的是「url-pattern」中*d的路徑部分
3. getContextPath():獲取項目的根路徑
4. getRequestURI:獲取根路徑到地址結尾
5. getRequestURL:獲取請求的地址連接（瀏覽器中輸入的地址）
6. getServletContext().getRealPath(「/」):獲取「/」在機器中的實際地址
7. getScheme():獲取的是使用的協議(http 或https)
8. getProtocol():獲取的是協議的名稱(HTTP/1.11)
9. getServerName():獲取的是域名(xxx.com)
10. getLocalName:獲取到的是IP