如果带WebRoot，那么js、css、img都应该放到WebRoot目录下，否则访问会有问题。千万不要放在WEB-INF下，因为WEB-INF下的内容只有服务器转发可以访问到，出于安全考虑。

如果不带有WebRoot目录，那么可以放在WEB-INF外面（建立的文件夹中）。

一、JSP、Servlet中的相对路径

a) 在JSP中

“/”代表站点（服务器）根目录http://127.0.0.1/

b)     在Servlet中

“/”代表Web应用的根目录http://127.0.0.1/JSP_Servlet_Path/

request.getRequestDispatcher("/a/a.jsp").forward(request, response);

相对路径/a/a.jsp中/相对于web应用的根目录，所以相当于请求跳转到绝对路径

response.sendRedirect("/JSP_Servlet_Path/b/b.jsp");

因为重定向中的方法是传递给浏览器，用于重新发送请求的，而在浏览器端“/”代表，相对于站点根目录，所以这里必须要加上/JSP_Servlet_Path，这样浏览器重新请求的地址为：http://127.0.0.1/JSP_Servlet_Path/b/b.jsp

package com.jsp_servlet_path.rqq; 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 JSP_Servlet extends HttpServlet {     @Override    public voiddoGet(HttpServletRequest request, HttpServletResponse response)                    throwsServletException, IOException {                               doPost(request,response);    }     @Override    public voiddoPost(HttpServletRequest request, HttpServletResponse response)                        throwsServletException, IOException {               System.out.println(request.getContextPath());                //请求转发，在服务器端，"/"代表（相对于）web应用http://localhost:8000/JSP_Servlet_Path/               //所以请求转发的绝对路径为http://localhost:8000/JSP_Servlet_Path/a/a.jsp                // request.getRequestDispatcher("/a/a.jsp").forward(request,response);               //请求重定向，将方法中的地址参数传递给浏览器，让浏览器重新发送请求，               //"/"代表（相对于）服务器站点http://localhost:8000/               //所以相当于浏览器重新请求了绝对路径http://localhost:8000/JSP_Servlet_Path/b/b.jsp               response.sendRedirect("/JSP_Servlet_Path/b/b.jsp");               //response.sendRedirect(request.getContextPath()+ "/b/b.jsp");    }}

二、JSP中加入basePath

<%    String path = request.getContextPath();    String basePath= request.getScheme()+"://"        +request.getServerName()+":"        +request.getServerPort()+path+"/";%>
    
     <%=basePath%>">
    

    注：相当于所有的href相对路径前面都加入了：

               http://localhost:8000/JSP_Servlet_Path/

三、JSP与Servlet相互访问

    
    
       
     
          
      
       JSP_Servlet
          
      
       com.jsp_servlet_path.rqq.JSP_Servlet
        
       
     
          
      
       CopyOfJSP_Servlet
          
      
       com.jsp_servlet_path.rqq.CopyOfJSP_Servlet
        
        
     
          
      
       JSP_Servlet
          
      
       /servlet/JSP_Servlet
        
       
     
          
      
       CopyOfJSP_Servlet
          
      
       /servlet/CopyOfJSP_Servlet
        
        
     
          
      
       index.jsp
        
     
    

<%@ page language="java"import="java.util.*"pageEncoding="GBK"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%>      
    
     <%=basePath%>">      
              
     
               
      
                
       
                    
        
                  
         
                   
               
          
              This is index.jsp page. 
           
   <%--href中隐含了basePath，因为
           
            <%=basePath%>">--%>   
            
             a.jsp(a/a.jsp)
             
   
             
              a.jsp(/JSP_Servlet_Path/a/a.jsp)
              
   
              
               c.jsp(a/c/c.jsp)
               
   
               
                e.jsp(a/c/e/e.jsp)
                
   
                
                 
   
                 
                  
   
                  
                   JSP_Servlet(servlet/JSP_Servlet)
                   
                    JSP_Servlet(/JSP_Servlet_Path/servlet/JSP_Servlet)
                    
    
                    
                     请求JSP_Servlet，并转发给CopyOfJSP_Servlet  
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      
     
    

package com.jsp_servlet_path.rqq; 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 JSP_Servlet extends HttpServlet {     @Override    public voiddoGet(HttpServletRequest request, HttpServletResponse response)                    throwsServletException, IOException {                               doPost(request,response);    }     @Override    public voiddoPost(HttpServletRequest request, HttpServletResponse response)                        throwsServletException, IOException {            System.out.println(request.getContextPath());            //请求转发，在服务器端，"/"代表（相对于）web应用http://localhost:8000/JSP_Servlet_Path/            //所以请求转发的绝对路径为http://localhost:8000/JSP_Servlet_Path/a/a.jsp            // request.getRequestDispatcher("/a/a.jsp").forward(request,response);            //请求重定向，将方法中的地址参数传递给浏览器，让浏览器重新发送请求，            //"/"代表（相对于）服务器站点http://localhost:8000/            //所以相当于浏览器重新请求了绝对路径http://localhost:8000/JSP_Servlet_Path/b/b.jsp            response.sendRedirect("/JSP_Servlet_Path/b/b.jsp");            //response.sendRedirect(request.getContextPath()+ "/b/b.jsp");             Stringstr_i = request.getParameter("i");             int i =new Integer(str_i);             switch(i) {                    case 0:                        request.getRequestDispatcher("/index.jsp").forward(request,response);                        System.out.println("index.jsp");                        break;                    case 1:                        request.getRequestDispatcher("/a/a.jsp").forward(request, response);                        System.out.println("a.jsp");                        break;                    case 2:                        request.getRequestDispatcher("/b/b.jsp").forward(request,response);                        System.out.println("b.jsp");                        break;                    case 3:                        request.getRequestDispatcher("/a/c/c.jsp").forward(request,response);                        System.out.println("c.jsp");                        break;                    case 100:                        request.getRequestDispatcher("/servlet/CopyOfJSP_Servlet").forward(request,response);                        System.out.println("forward to CopyOfJSP_Servlet");                        break;                    default:                        System.out.println("default");                        return;             }    }}