servlet servletContext【回転】

 

         ServletContext   。
   WEB      ，     WEB            ServletContext  ，     web  。

   ServletConfig      ServletContext     ，       servlet ，    ServletConfig.getServletContext    ServletContext  。

      WEB      Servlet     ServletContext  ，  Servlet        ServletContext       。ServletContext         context   。

1.  Servlet  ServletContext        。

 InitServlet Service     ServletContext           

/*  ServletContext  */  

ServletContext context = this.getServletContext();   

//           

context.setAttribute("name", "haha"); 

    Servlet   ServletContext            

/*  ServletContext  */  

ServletContext context = this.getServletContext();   

//          

String name = context.getAttribute("name");   

System.out.println("       :"+name);  

2.  WEB        。

 web.xml               。

<web-app>   

 <context-param>   

<param-name>url</param-name>   

<param-value>jdbc:mysql://localhost:3306/4g</param-value>   

 </context-param>   

<context-param>   

 <param-name>password</param-name>   

 <param-value>1314qr</param-value>   

 </context-param>   

 <context-param>   

  <param-name>user</param-name>   

  <param-value>root</param-value>   

  </context-param>   

</web-app>  

 DemoServlet doPost                 :   

/*  ServletContext  */  

 ServletContext context = this.getServletContext();   

/*       */  

//               

String url = context.getInitParameter("url"); 

 //  web.xml                       

 Enumeration<String> enumer = context.getInitParameterNames();   

while(enumer.hasMoreElements()){   

String name = enumer.nextElement();   

 String value = context.getInitParameter(name);   

 System.out.println(name+"=========="+value);   

    }   

2.  Servlet   ：

    Servlet          :  

/*   ServletContext          */  

ServletContext context = this.getServletContext();   

 // request     name      

request.setAttribute("name", "haha");   

 /*          RequestDispatcher  */  

RequestDispatcher  rd  = context.getRequestDispatcher("/index.jsp");   

//                     

rd.forward(request, response);   

  //rd.include(request, response);   

  ：forward include    

forward                 servlet. include     servlet          .

（forward                      。         Servlet ， 

        Servlet         ，   Servlet      。      

   include      Servlet     Servlet         ，    Servlet           ）

3.  ServletContext        。  

      (properties  （    ）)     

   properties     :   

url=jdbc\:mysql\://localhost\:3306/3g ; 

user=root;

password=root;  

         :   

/*  ServletContext  */  

ServletContext context = this.getServletContext();     

//         

URL url = context.getResource("WEB-INF/classes/db.properties");   

InputStream is =  url.openStream();   

//        

 /*  db.properties  */  

String path =context.getRealPath("WEB-INF/classes/db.properties");   

 /*              */  

File file = new File(path);   

 /*  file          */  

InputStream is = new FileInputStream(file);   

//        

InputStream is = context.getResourceAsStream("WEB-INF/classes/db.properties ");    

            ：    

  /*  properties   */  

     Properties prop = new Properties();   

     //           （     ）。   

      prop.load(is);   

      Set<String> set = prop.stringPropertyNames();   

       //  set     

       Iterator<String> it = set.iterator();   

       while(it.hasNext()){   

           String key = it.next();   

           String value = prop.getProperty(key);   

           System.out.println(key+"-----"+value);   

              }