nullpointerException

hi to all
i m using struts 2 but i m getting a nullpointerexception which is frustrating me my code is as
please help me to solve the problem .
thanks in advance.

package com.action;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.struts2.convention.annotation.Action;
import org.apache.struts2.convention.annotation.Namespace;
import org.apache.struts2.convention.annotation.ParentPackage;
import org.apache.struts2.convention.annotation.Result;
import org.apache.struts2.convention.annotation.ResultPath;
import org.apache.struts2.interceptor.ServletRequestAware;
import org.apache.struts2.interceptor.ServletResponseAware;

import com.opensymphony.xwork2.ActionSupport;

@ParentPackage(value = "default")
@Namespace("/")
@ResultPath(value = "/")

public class userId extends ActionSupport implements ServletRequestAware,ServletResponseAware{
	
	
	
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	
	
	
	private HttpServletRequest request;
	private HttpServletResponse response;
	
	@Action(value="",results={@Result(name="success" , type="tiles" , location="universityIndex")})

public String execute() {
		String url = request.getRequestURL().toString();

// Getting servlet request query string.
        String queryString = request.getQueryString();
        // Getting request information without the hostname.
        String uri = request.getRequestURI();

String scheme = request.getScheme();
        String serverName = request.getServerName();
        int portNumber = request.getServerPort();
        String contextPath = request.getContextPath();
        @SuppressWarnings("unused")
		String servletPath = request.getServletPath();
        String pathInfo = request.getPathInfo();
        String query = request.getQueryString();
        System.out.println("queryString"+queryString+"url"+url+"uri"+uri+"scheme"+scheme+"serverName"+serverName+"portNumber"+portNumber+"query"+query+"contextPath"+contextPath+"pathInfo"+pathInfo);
		return SUCCESS;
    }

public void setServletRequest(HttpServletRequest request) {
		// TODO Auto-generated method stub
		
	}
	
	public HttpServletRequest getServletRequest(){
	    return request;
	  }

public void setServletResponse(HttpServletResponse response) {
		// TODO Auto-generated method stub
		
	}
	
	public HttpServletResponse getServletResponse(){
	    return response;
	  }

}

stack trace is :-

java.lang.NullPointerException

com.action.userId.execute(userId.java:40)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    java.lang.reflect.Method.invoke(Method.java:597)
    com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:452)
    com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:291)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:254)
    com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:263)
    org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:133)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:207)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:207)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:190)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:94)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:243)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:267)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:142)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:166)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:176)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:190)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:187)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52)
    org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:485)
    org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
    org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)
    org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1254)
    org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:481)
    org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:119)
    org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:516)
    org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:230)
    org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:956)
    org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:411)
    org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:188)
    org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:891)
    org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:117)
    org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:247)
    org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:151)
    org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:114)
    org.eclipse.jetty.server.Server.handle(Server.java:353)
    org.eclipse.jetty.server.HttpConnection.handleRequest(HttpConnection.java:598)
    org.eclipse.jetty.server.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:1059)
    org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:590)
    org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:212)
    org.eclipse.jetty.server.HttpConnection.handle(HttpConnection.java:427)
    org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:510)
    org.eclipse.jetty.io.nio.SelectChannelEndPoint.access$000(SelectChannelEndPoint.java:34)
    org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:40)
    org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:450)
    java.lang.Thread.run(Thread.java:662)

I fixed your code tags for you.
Your code doesn't match your stack trace (line 40 is blank here). What's on line 40 in the code you are really using?

the error is on this code line
<code>
String url = request.getRequestURL().toString();
</code>

I have pasted one line below from my editor thats why the stack trace shows the error on 40 line
in my code this line is on line 40
know can you please help me to solve it