java - Attempting to access web.xml getting NoInitialContextException -

i building web application class (yes homework assignment). using eclipse , tomcat 8. have following code service factory:

package com.orderonline.model.service.factory;   import javax.naming.context; import javax.naming.initialcontext;  import com.orderonline.model.service.interfaces.iservice;  public class servicefactory {     public iservice getservice(string name) throws exception     {         try         {             class<?> newclass = class.forname(getimplname(name));             return (iservice)newclass.newinstance();         }         catch(exception e)         {             throw new exception(name);         }     }      private string getimplname(string name) throws exception     {         context initctx = new initialcontext();         context envctx = (context) initctx.lookup("java:comp/env");          string lookupclass = (string) envctx.lookup(name);         return lookupclass;     } } 

i expected in web.xml file located @ orderonline/webcontent/web-inf/web.xml following:

  <env-entry>     <env-entry-name>iusersvc</env-entry-name>     <env-entry-type>java.lang.string</env-entry-type>     <env-entry-value>com.orderonline.model.service.interfaces.iusersvc</env-entry-value>   </env-entry> 

instead getting exception thrown when line run:

context envctx = (context) initctx.lookup("java:comp/env"); 

the exception is:

javax.naming.noinitialcontextexception: need specify class name in environment or system property, or applet parameter, or in application resource file:  java.naming.factory.initial 

i new @ this, missing important peice of information me, , more happy provide more information needed. appreciate assistance can provided me read env-entry-value web.xml file.

you need initial context factory stated in this answer on so.

    system.setproperty(context.initial_context_factory,               "org.apache.naming.java.javaurlcontextfactory");