“ Singleton Session Bean”，用于存储应用程序范围的信息Java EE 6

Question

I write a Java ee 6 application on a jboss-as-7 application server. I want to have a “Singleton Session Bean” to store application wide informations in a list “mediaDataList”.

A statless session bean “ClassA“ write some object to this list and a webservice reads the informations in the “mediaDataList” list.

@Singleton
@ConcurrencyManagement(ConcurrencyManagementType.CONTAINER)
@Lock(LockType.WRITE)
public class MediaDataSafe {

    private final List<MediaData> mediaDataList = new ArrayList<MediaData>();

    @Inject
    Logger log;

    @PostConstruct
    void init() {
        // read from HD and store in mediaDataList
    }


    // just read the list...
    public List<MediaData> getMediaDataList() {
        return mediaDataList;
    }

    // write to list
    public void writeMediaDataSafe(...) {
        mediaDataList.add(auraMediaData);
    }
}


@Stateless
public class ClassA {

    @Inject
    MediaDataSafe mediaDataSafe;

    //write in list of singleton
    public void write(...) {
        mediaDataSafe.writeMediaDataSafe(...);
    }
}

@WebService(serviceName = "MyWebService", endpointInterface = "com.WebService")
public class MyWebService implements com.bla.WebService {

    //...

    @Inject
    transient MediaDataSafe mediaDataSafe;

    //read from list in singleton
    public MediaList getMediaList(...){
        mediaDataSafe.getMediaDataList(...);
    }
}

My problem is, it seems that there exists two “signleton bean” in my system! If “ClassA “ write some new values to the list, I can't read this new values with my webservice. The webservice returns always the same list. (it contains the state on init!)

What do I wrong? Do I misunderstanding something here about “Singleton Session Bean”?

Answer 1

It looks fine so far for me, since a Singleton is instantiated once per application, the only reasons I can think of leading possibly to the described behaviour is something in the direction of several deployments of the same application.

Maybe it helps to read the following parts of the Java EE 6 tutorial carefully to find the problem:

• Singleton Session Beans
• Singleton Session Bean Example