getServletContext和getServletConfig的getInitParameter方法(读取文件存储地址)

<?xml version="1.0" encoding="UTF-8"?> 
<web-app version="2.4" 
... 
   <context-param> 
     <param-name>P1 </param-name> 
     <param-value>This Is web-app Value </param-value>
   </context-param> 
... 
<servlet> 
    <servlet-name>HelloServlet </servlet-name> 
   <servlet-class>suman.Servlet.HelloServlet </servlet-class> 
   <init-param> 
        <param-name>P1 </param-name> 
        <param-value>This is the servlet value </param-value> 
   </init-param> 
</servlet> 

... 
</web-app> 

public class HelloServlet extends HttpServlet { 

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

... 
String s1 = getServletConfig().getInitParameter("P1"); 
String s2 = getServletContext().getInitParameter("P1"); 
String s3 = getServletConfig().getServletContext().getInitParameter("P1"); 
String s4 = getInitParameter("P1"); 

out.println("SumanChina_DoGet"); 
out.println(" <br>"); 
out.println("s1:"+s1+" <br>"); 
out.println("s2:"+s2+" <br>"); 
out.println("s3:"+s3+" <br>"); 
out.println("s4:"+s4); 
... 
} 
}

输出结果：
 s1:This is the servlet value 
 s2:This Is web-app Value 
 s3:This Is web-app Value 
 s4:This is the servlet value

 1：getServletContext()取得的是 <context-param>配置的参数 
 2：getServletConfig()取得的是 <servlet> <init-param>配置的参数
 3：getServletContext()
应用于整个web App,而getServletConfig()仅应用于当前Servlet。 
但是ServletConfig对象拥有ServletContext的引用。所以可以通过getServletConfig()来获得web 
App的初始值。