hibernate in servlet - threadsafe

[Amy Saari]

Hi All

We're really having a hard time trying to figure out if our code is really threadsafe. We have a web app that contains spring-injected services that use a dao layer to get to the database via Hibernate. We injected the services into INSTANCE variables in the servlet - so every request that comes in becomes a thread that uses those same service objects. The service object contains a dao object that is used to access the database via hibernate (oracle in this case).

So, for example, the contactService is an instance variable in the this servlet

    
public class SupervisorSelectCounselorAction extends Action {
    private TSSUserService userService;
    private ContactService contactService;
    private ContactRecordingAuthorizationService authorizationService;

this call is made from the servlet to the service

    
List lContactList = 
                contactService.findSupervisorContactList(
                    authenticatedUser.getId(), displayOnlyIncompleteContacts );

in the ContactService class we use a dao class:

    
public class ContactServiceImpl implements ContactService {

	private ContactDao contactDao;

and make this call:

    
return contactDao.findSupervisorContactList(
            pUserId, lContactStartRange, pShowIncompleteContactsOnly );

in the ContactDao class is the method:

    
public List findSupervisorContactList(
        DoubleIntId pUserId,
        Date pOldestContactStartTime,
        boolean pShowIncompleteContactsOnly ) {

        String lQuery = "SELECT distinct c FROM Contact c, TSSUserSummary tus, ";
        lQuery +=
            "SupervisedTSSUser stu " +
            "WHERE stu.supervisorId.id=" + pUserId.getId() +
            "AND stu.supervisorId.origId=" + pUserId.getOrigId() +
            "AND tus.id.id=stu.userId.id and tus.id.origId=stu.userId.origId " +
            "AND stu.userRollupTypeCode=1 " +
            "AND tus.id.id=c.tssUserId.id and tus.id.origId=c.tssUserId.origId ";

        if ( pShowIncompleteContactsOnly ) {
            lQuery += "AND c.completeFlag='N' ";
        }

        lQuery += "AND to_char(c.startGMTTS,'YYYYMMDD hh24:mi:ss') > ";
        SimpleDateFormat lFormatter = new SimpleDateFormat( "yyyyMMdd HH:mm:ss" );
        lQuery += "'" + lFormatter.format( pOldestContactStartTime ) + "' ";

        lQuery += "ORDER BY c.startGMTTS";
        Query hqlQuery = getSession().createQuery( lQuery );
        List lContactList = hqlQuery.list();
    
        if ( lContactList != null && lContactList.size() > 0 ) {
            Iterator lIterator = lContactList.iterator();
            Contact lContact = null;
            while ( lIterator.hasNext() ) {
                lContact = ( Contact )lIterator.next();
                populateNonPersistentDescriptionFields( lContact );
            }
        }
        return lContactList;
    }

From what I understand the org.hibernate.Query is not threadsafe. So is it possible our code is not threadsafe because each thread started by the servlet container is using the same service and dao objects?

Thanks for any help.
Amy

[Salil Vverma]

Hi Amy,

Servlet's instance variables are not thread safe. so the following variable might have thread safety problem.

   
    
public class SupervisorSelectCounselorAction extends Action {
    private TSSUserService userService;
    private ContactService contactService;
    private ContactRecordingAuthorizationService authorizationService;

 

org.hibernate.Query is not thread safe but it would not be a problem in your code, reason being you are creating hqlQuery local object rather than an instace object. Each thread (each execution) using findSupervisorContactList function would have its own hqlQuery object in the stack.

[Mark Spritzler]

The architecture you described IS thread safe.

The service class is not state, but a service class. In Spring it is instantiated just once and can receive calls from many threads simultaneously.

The architecture you described is exactly how you want it set up.

Mark

[Amy Saari]

Thank you both very much

Amy