NullPointerException while retrieving session information through ActionContext

Question

I am currently working on an organization's framework to migrate it to Struts 2 from Webworks using IBM WebSphere 7. I followed the steps listed below:

1) Imported the struts2-core-2.3.16.jar along with other dependencies JAR.

2) Renamed xwork.xml to struts.xml and changed the setting in web.xml to use StrutsPrepareAndExecuteFilter.

3)Replaced webwork JAR code with struts2 code and xwork code to xwork2 code respectively in the Interceptors and Controllers.

The server starts up fine and the deployment takes place fine. When I start the Application, I get a NullPointerException which happens because the code in one of the Interceptors tries to retrieve the session information and gets a null response. I debugged it and saw that the session information is not available in the ActionContext or the ActionInvocation instance. What could be the possible reasons for this?

Stack trace: (For confidentiality purposes, I have hidden the name of the organization)

java.lang.NullPointerException 
    com.somecompany.merchandiseplanning.controller.AbstractAuthorizationInterceptor.getBusinessServicesString(AbstractAuthorizationInterceptor.java:57)
    com.somecompany.merchandiseplanning.controller.AbstractAuthorizationInterceptor.initializeBusinessServices(AbstractAuthorizationInterceptor.java:63)
    com.somecompany.merchandiseplanning.controller.AbstractAuthorizationInterceptor.intercept(AbstractAuthorizationInterceptor.java:35)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)
    org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:562)
    org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
    org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:99)
    com.ibm.ws.webcontainer.filter.FilterInstanceWrapper.doFilter(FilterInstanceWrapper.java:188)
    com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:116)
    com.ibm.ws.webcontainer.filter.WebAppFilterChain._doFilter(WebAppFilterChain.java:77)
    com.ibm.ws.webcontainer.filter.WebAppFilterManager.doFilter(WebAppFilterManager.java:908)
    com.ibm.ws.webcontainer.filter.WebAppFilterManager.invokeFilters(WebAppFilterManager.java:997)
    com.ibm.ws.webcontainer.extension.DefaultExtensionProcessor.invokeFilters(DefaultExtensionProcessor.java:1043)
    com.ibm.ws.webcontainer.extension.DefaultExtensionProcessor.handleRequest(DefaultExtensionProcessor.java:963)
    com.ibm.ws.webcontainer.webapp.WebApp.handleRequest(WebApp.java:3933)
    com.ibm.ws.webcontainer.webapp.WebGroup.handleRequest(WebGroup.java:276)
    com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:931)
    com.ibm.ws.webcontainer.WSWebContainer.handleRequest(WSWebContainer.java:1583)
    com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:186)
    com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:445)
    com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewRequest(HttpInboundLink.java:504)
    com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.processRequest(HttpInboundLink.java:301)
    com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.ready(HttpInboundLink.java:275)
    com.ibm.ws.tcp.channel.impl.NewConnectionInitialReadCallback.sendToDiscriminators(NewConnectionInitialReadCallback.java:214)
    com.ibm.ws.tcp.channel.impl.NewConnectionInitialReadCallback.complete(NewConnectionInitialReadCallback.java:113)
    com.ibm.ws.tcp.channel.impl.AioReadCompletionListener.futureCompleted(AioReadCompletionListener.java:165)
    com.ibm.io.async.AbstractAsyncFuture.invokeCallback(AbstractAsyncFuture.java:217)
    com.ibm.io.async.AsyncChannelFuture.fireCompletionActions(AsyncChannelFuture.java:161)
    com.ibm.io.async.AsyncFuture.completed(AsyncFuture.java:138)
    com.ibm.io.async.ResultHandler.complete(ResultHandler.java:204)
    com.ibm.io.async.ResultHandler.runEventProcessingLoop(ResultHandler.java:775)
    com.ibm.io.async.ResultHandler$2.run(ResultHandler.java:905)
    com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1604)

The piece of code that is enclosed in the error stack and which tries to retrieve the session is :

private String getBusinessServicesString(){

Map session = ActionContext.getContext().getSession();  //Error : No session retrived

UserInfo userInfo = (UserInfo) session.get("userinfo");
return userInfo.getUserLoginId() + "_BUSINESS_SERVICES";
    }

I tried replacing it with

Map session = actionInvocation.getInvocationContext().getSession();

with actionInvocation being an instance of ActionInvocation passed in the intercept method of the Interceptor but I get the same null response there.

Any help will be much appreciated!

Answer 1

You will get session from ActionContext in the action class only when the action is initiated by the struts2 filter.

In this case implement SessionAware interface in your class(containing method getBusinessServicesString()) and use the session attribute of the interface to get session. Suppose ABC is your action class then it can be done as below.

public class ABC extends ActionSupport implements SessionAware {

    private Map session;

 public void setSession(Map session) {
  this.session = session;
 }

 public Map getSession() {
  return session;
 }

    private String getBusinessServicesString(){
      session = ActionContext.getContext().getSession();  
      UserInfo userInfo = (UserInfo) session.get("userinfo");
      return userInfo.getUserLoginId() + "_BUSINESS_SERVICES";
    }

}