web项目路径问题

路径
    相对路径
        URL中第一个字符不为“/”
        request.getRequestDispatcher("b");
        相对于该代码所在的位置，指的是java文件的位置。
    
    绝对路径
        URL中第一个字符不为""
        request.getRequestDispatcher("/b")
        前台
            /代表的是服务器的根目录，注意：是服务器的根目录
            使用例子：
                html页面，jsp页面，重定向
            "ip:port/"    http://localhost:8080/    webapps
        后台
            /代表的是项目的根目录 注意：是项目的根目录
            使用例子：
                request.getRequestDIspatcher("b")
                web.xml
                    <url-pattern>/a</url-pattern>
                    http://localhost:8080/helloWorld/a
            webapps/helloWorld ---hhtp://ip:port/helloWorld
        
     Servlet
       其路径由web.xml中的<url-pattern>/basic</url-pattern>
        http://localhost:8888/jd1508/basic
        路径并不是说他的类所在的目录
     静态资源
       其路径由其所在的项目的实际路径来决定，前提是没有放在WEB-INF下
       webapps/jd1508/html/a.html
       http://localhost:8888/jd1508/html/a.html

服务器根目录  webapps --  http://ip:port/
     项目的根目录  webapps/jd1508  --  http://ip:port/jd1508
    
TOAHtmlServlet
    http://localhost:8888/jd1508/toAHtml
    --->  
    {  重定向，day7/a.html  浏览器地址发生变化}
    http://localhost:8888/jd1508/day7/a.html
    a.html
      ---> TAServlet
      http://localhost:8888/jd1508/ta

TOAHtmlServlet
    http://localhost:8888/jd1508/toAHtml
    --->  
    {  内部跳转，/day7/a.html  浏览器地址不发生变化}
    http://localhost:8888/jd1508/toAHtml
    a.html
      <a href="../a.html"></a>
      ---> TAServlet
      http://localhost:8888/jd1508/ta

一个路径问题的小例子：

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" alt="" />

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>a.html</title>

    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="this is my page">
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">

    <!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
    <base  target="http://127.0.0.1:8080/ServletDemo02">
  </head>

  <body>
      <!-- 需要访问到aServlet，怎么办呢？，第一种路径出现问题，表示 http://127.0.0.1:8080/aServlet-->
   <a href="/aServlet">AServlet</a><br/>
   <!-- 这种方式可以，最好是在jsp中使用，因为有时候你无法获知你的项目名 -->
   <a href="/ServletDemo02/aServlet">AServlet</a><br/>
   <!--
           这种相对路径的方式，先找到项目的根目录然后找到servlet，貌似可以，不过可能出现路径问题，问题会出现在哪呢？
           因为相对上一级目录中查找对应的servlet，本次的路径不是固定的，一般使用内部跳转的话，浏览器的地址栏不会发生
           变化，就会导致上一级目录发生变化而产生路径问题
           http://127.0.0.1:8080/ServletDemo02/toAHtml
           http://127.0.0.1:8080/aServlet
       -->
   <a href="../aServlet">AServlet</a><br/>
   <!-- 我们可以使用base属性达到想要的效果，就是在页面设置一个基本地址，然后使用相对路径,设置base的target属性即可
           。不过有时候即使设置了base，如果逻辑太过混乱也会出现路径问题，这个时候你就需要多琢磨了 -->
   <a href="aServlet">AServlet</a><br/>
  </body>
</html>
package com.servlet;

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 ToAHtml extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public ToAHtml() {
        super();
    }
    public void destroy() {
        super.destroy();
    }
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doPost(request,response);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        request.getRequestDispatcher("/html/a.html").forward(request, response);
        //response.sendRedirect("/html/a.html");
    }

    public void init() throws ServletException {
    }

}
package com.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class AServlet extends HttpServlet {
    /**
     *
     */
    private static final long serialVersionUID = 1L;
    public AServlet() {
        super();
    }

    public void destroy() {
        super.destroy();
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doPost(request,response);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        PrintWriter out=response.getWriter();
        out.write("AServlet");
        out.close();
    }
    public void init() throws ServletException {
    }

}