Problem with execAndWait interceptor

[Bilal A. Siddiqui]

Hi All

my xml file looks like this.

  <interceptor-ref name="defaultStack" />
                <interceptor-ref name="execAndWait" />
            
            <result name="success">/Homee.jsp</result>
            <result name="error">/Login.jsp</result>
            <result name="input">/Login.jsp</result>
            <result name="wait">/Wait.jsp</result>  

after executing its giving me null pointer exception.

if i remove this wait part its running fine.

[David Newton]

...

"its giving me null pointer exception" is not helpful on its own. *What* is giving you the NPE?

[Bilal A. Siddiqui]

The action on which i am applying this execAndWait interceptor is doing 2 things

1. Its validating username and passowrd

2. If validation succeeds it fetches some data corresponding to the user, puts that data in a list and save that list in session.


without execAndWait its running fine, as soon as i include execAndWait it gives me NPE.

[David Newton]

...

How could anyone possibly diagnose an NPE if we don't know where the NPE is occurring? Is it in S2 code? XWork code? Your code? Third-party library code? Zimbabwe? Stack traces are provided for a reason.

[Bilal A. Siddiqui]

Hi David,

java.lang.NullPointerException
at com.apt.action.Login.execute(Login.java:152)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:404)
at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:267)
at org.apache.struts2.interceptor.BackgroundProcess$1.run(BackgroundProcess.java:56)
at java.lang.Thread.run(Thread.java:595)

the line on which this error is really pin pointing is

 request.getSession().setAttribute("empIds", empIds);   

and this is excatly what i am doing after username validation

  try{
                                   empIds=app.setEmployees(loginID);

                                applicationList = app.setApplication(pf.emp.getDepartmentID(), pf.emp.getLocationID(),empIds);
                                studentInfoList = ast.setStudents(applicationList);
                                stdDisplayList = disp.dataDisplay(studentInfoList, applicationList);
                               }catch(Exception e)
                               {
                                   System.out.println("Login Data "+e);
                               }

                               _request.getSession().setAttribute("empIds", empIds);
                               _request.getSession().setAttribute("applicationList", applicationList);
                                _request.getSession().setAttribute("stdDisplayList", stdDisplayList);   

[David Newton]

Your session is getting lost?! Can you confirm that somehow?

[Bilal A. Siddiqui]

Hi David,

You were right. The session is getting lost.

when i am calling this line

 applicationList = app.setApplication(pf.emp.getDepartmentID(), pf.emp.getLocationID(),empIds);   

this method is being called

   public List setApplication(int departmentID, int officeID,Vector empIds) throws ClassNotFoundException, SQLException, Exception {

        
        Statement st = con.createStatement();
        for (int i = 0; i < empIds.size(); i++) {
            str = "select * from Vw_ApplicationProgressDetails where (CounslerID='" + empIds.get(i) + "' or appMemberID='" + empIds.get(i) + "' or visaMemberID='" + empIds.get(i) + "')";
           //System.out.println(str);
            rs = st.executeQuery(str);
            while (rs.next()) {
                Application app = new Application();
                app.setApplicationID(Integer.parseInt(rs.getString("ApplicationID")));
                app.setStudentID(Integer.parseInt(rs.getString("StudentID")));
                app.setCourseID(Integer.parseInt(rs.getString("CourseID")));
                app.setUniversityID(Integer.parseInt(rs.getString("universityID")));
                app.setCountryID(Integer.parseInt(rs.getString("countryID")));
                app.setIntakeID(Integer.parseInt(rs.getString("IntakeID")));
                app.setCounStatusID(Integer.parseInt(rs.getString("counStatusID")));
                app.setCounselorStatusDate(rs.getString("counStatusDate"));
                app.setCounslerID(Integer.parseInt(rs.getString("CounslerID")));
                app.setCounselorDeptID(Integer.parseInt(rs.getString("counselorDeptID")));
                app.setCounselorLocID(Integer.parseInt(rs.getString("counselorLocationID")));
                app.setAppStatusID(Integer.parseInt(rs.getString("appStatusID")));
                app.setApplicationStatusDate(rs.getString("applStatusDate"));
                app.setAppMemberID(Integer.parseInt(rs.getString("appMemberID")));
                app.setAppDeptID(Integer.parseInt(rs.getString("appDeptID")));
                app.setAppLocID(Integer.parseInt(rs.getString("appLocationID")));
                app.setVisaStatusID(Integer.parseInt(rs.getString("visaStatusID")));
                app.setVisaStatusDate(rs.getString("VISAStepDate"));
                app.setVisaMemberID(Integer.parseInt(rs.getString("visaMemberID")));
                app.setVisaDeptID(Integer.parseInt(rs.getString("visaDeptID")));
                app.setVisaLocID(Integer.parseInt(rs.getString("visaLocationID")));
                //    app.setIELTS(Byte.parseByte(rs.getString("IELTS")));
                //   app.setELICOS(Byte.parseByte(rs.getString("ELICOS")));
                app.setCampusName(rs.getString("CampusName"));
               
                applicationList.add(app);

            }
            rs.close();

        }
        ConnectionPool.releaseConnection(con);
        return applicationList;
    }
  

now in this method if don't execute the query
i mean this line

  rs = st.executeQuery(str);  

session is maintained, but if i execute session is getting lost.

Now how should i maintain this session?

[David Newton]

I don't see how that code could make the session go away; it's not related to session handling at all. I think something else is wrong.

In any case, it doesn't seem to be a Struts issue.

Btw, BeanUtils.copyProperties().

[J Owens]

execAndWait Interceptor?

the exec and wait interceptor is declaired in your struts.xml file like

<action name="someAction" class="com.examples.SomeAction">
    <interceptor-ref name="completeStack"/>
    <interceptor-ref name="execAndWait">
        <param name="delay">1000<param>
        <param name="delaySleepInterval">50<param>
    <interceptor-ref>
    <result name="wait">longRunningAction-wait.jsp</result>
    <result name="success">longRunningAction-success.jsp</result>
</action>

its my understanding that the wait page is called from a bkground thread, which makes me wonder
if this newly created (temporary) thread would have access to the session of the original thread (I'm unsure).

perhaps this is why the success page (called from/with original thread) can get stuff from the session just fine?
If this is true it looks like a slight hack might be necessary?

above code from http://struts.apache.org/2.0.6/docs/execute-and-wait-interceptor.html

[J Owens]

Important: Because the action will be running in a seperate thread, you can't use ActionContext because it is a ThreadLocal.
This means if you need to access, for example, session data, you need to implement
SessionAware rather than calling ActionContext.getSesion().

from: http://struts.apache.org/2.0.6/docs/execute-and-wait-interceptor.html