at sitetemplate.classes.SiteTemplateMethods.userName(SiteTemplateMethods

My following method is not working: //sorry typo

view plaincopy to clipboardprint?
Note: Text content in the code blocks is automatically word-wrapped
public String userName()throws IOException{  
      
    String msg="";    
 
        HttpServletRequest req = null;  
        HttpSession session=req.getSession();  
        String userName=(String)session.getAttribute("name");     
 
            if(userName==null || userName.equals("") || userName.equalsIgnoreCase("null")){   
            msg="";  
            }  
            else{  
            msg= userName;  
            }  
    return msg;  
    } 
public String userName()throws IOException{
 
 String msg=""; 

  HttpServletRequest req = null;
  HttpSession session=req.getSession();
  String userName=(String)session.getAttribute("name"); 

   if(userName==null || userName.equals("") || userName.equalsIgnoreCase("null")){ 
   msg="";
   }
   else{
   msg= userName;
   }
 return msg;
 }

Error stack Trace:
view plaincopy to clipboardprint?
Note: Text content in the code blocks is automatically word-wrapped
<br>    at sitetemplate.classes.SiteTemplateMethods.userName(SiteTemplateMethods  
<br>    at globalcategories.classes.GlobalCategoriesManager.doGet(GlobalCategori  
<br>    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl  
<br>    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF  
<br>    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperV  
<br>    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextV  
<br>    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.j  
<br>    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.j  
<br>    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineVal  
<br>    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.jav  
<br>    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java  
<br>    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.proce  
<br>    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:44 
<br>    at java.lang.Thread.run(Thread.java:619) 
Yes, you just set it to null, so it's going to be null in line 2 and generate a null pointer exception.

Why is this code not in a servlet if you need references to the request and response?
I just passed req parameter from my servlet to my method and its working fine now