当 session 在 websphere 中失效时，Spring 视图 scope 不会被破坏

Question

I am using Springboot 1.5.9.RELEASE , JSF 2.2.20 (glassfish) , Primefaces 8 running on WebSphere 8.5.5.13 , and I have defined custom view scope, based on the following link:

https://github.com/jneat/spring-jsf

public class ViewScope implements Scope, HttpSessionBindingListener {

private static final long serialVersionUID = 1L;

private static final Log logger = LogFactory.getLog(ViewScope.class);

private final WeakHashMap<HttpSession, Set<ViewScopeViewMapListener>> sessionToListeners = new WeakHashMap<>();

@Override
public Object get(String name, ObjectFactory objectFactory) {
    Map<String, Object> viewMap = FacesContext.getCurrentInstance().getViewRoot().getViewMap();
    //noinspection SynchronizationOnLocalVariableOrMethodParameter
    if (viewMap.containsKey(name)) {
        return viewMap.get(name);
    } else {
        synchronized (viewMap) {
            if (viewMap.containsKey(name)) {
                return viewMap.get(name);
            } else {
                logger.trace("Creating bean " + name);
                Object object = objectFactory.getObject();
                viewMap.put(name, object);
                return object;
            }
        }
    }
}

@Override
public String getConversationId() {
    return null;
}

/**
 * Removing bean from the scope and unregister it destruction callback without executing them.
 *
 * @see Scope for more details
 */
@Override
public Object remove(String name) {
    Map<String, Object> viewMap = FacesContext.getCurrentInstance().getViewRoot().getViewMap();
    if (viewMap.containsKey(name)) {
        Object removed;
        synchronized (viewMap) {
            if (viewMap.containsKey(name)) {
                removed = FacesContext.getCurrentInstance().getViewRoot().getViewMap().remove(name);
            } else {
                return null;
            }
        }

        HttpSession httpSession = (HttpSession)FacesContext.getCurrentInstance().getExternalContext().getSession(true);
        Set<ViewScopeViewMapListener> sessionListeners;
        sessionListeners = sessionToListeners.get(httpSession);
        if (sessionListeners != null) {
            Set<ViewScopeViewMapListener> toRemove = new HashSet<>();
            for (ViewScopeViewMapListener listener : sessionListeners) {
                if (listener.getName().equals(name)) {
                    toRemove.add(listener);
                    FacesContext.getCurrentInstance().getViewRoot().unsubscribeFromViewEvent(PreDestroyViewMapEvent.class, listener);
                }
            }
            synchronized (sessionListeners) {
                sessionListeners.removeAll(toRemove);
            }
        }

        return removed;
    }
    return null;
}

/**
 * Register callback to be executed only on the whole scope destroying (not single object).
 *
 * @see Scope for more details
 */
@Override
public void registerDestructionCallback(String name, Runnable callback) {
    logger.trace("registerDestructionCallback for bean " + name);

    UIViewRoot viewRoot = FacesContext.getCurrentInstance().getViewRoot();
    ViewScopeViewMapListener listener = new ViewScopeViewMapListener(viewRoot, name, callback, this);

    viewRoot.subscribeToViewEvent(PreDestroyViewMapEvent.class, listener);

    HttpSession httpSession = (HttpSession)FacesContext.getCurrentInstance().getExternalContext().getSession(true);

    final Set<ViewScopeViewMapListener> sessionListeners;

    if (sessionToListeners.containsKey(httpSession)) {
        sessionListeners = sessionToListeners.get(httpSession);
    } else {
        synchronized (sessionToListeners) {
            if (sessionToListeners.containsKey(httpSession)) {
                sessionListeners = sessionToListeners.get(httpSession);
            } else {
                sessionListeners = new HashSet<>();
                sessionToListeners.put(httpSession, sessionListeners);
            }
        }
    }

    synchronized (sessionListeners) {
        sessionListeners.add(listener);
    }

    if (!FacesContext.getCurrentInstance().getExternalContext().getSessionMap().containsKey("sessionBindingListener")) {
        FacesContext.getCurrentInstance().getExternalContext().getSessionMap().put("sessionBindingListener", this);
    }

}

@Override
public Object resolveContextualObject(String key) {
    return null;
}

@Override
public void valueBound(HttpSessionBindingEvent event) {
    logger.trace("Session event bound " + event.getName());
}

/**
 * Seems like it called after our listeners were unbounded from HTTP session.
 * Looks like view scope is destroyed. But should we call callback or not is a big question.
 *
 * @see HttpSessionBindingListener for more details
 */
@Override
public void valueUnbound(HttpSessionBindingEvent event) {
    logger.trace("Session event unbound " + event.getName());
    final Set<ViewScopeViewMapListener> listeners;
    synchronized (sessionToListeners) {
        if (sessionToListeners.containsKey(event.getSession())) {
            listeners = sessionToListeners.get(event.getSession());
            sessionToListeners.remove(event.getSession());
        } else {
            listeners = null;
        }
    }
    if (listeners != null) {
        // I just hope that JSF context already done this job
        for (ViewScopeViewMapListener listener : listeners) {
            // As long as our callbacks can run only once - this is not such big deal
            listener.doCallback();
        }
    }
}

/**
 * Will remove the listener from the session set and unregister it from UIViewRoot.
 */
public void unregisterListener(ViewScopeViewMapListener listener) {
    logger.debug("Removing listener from map");
    HttpSession httpSession = (HttpSession)FacesContext.getCurrentInstance().getExternalContext().getSession(false);
    FacesContext.getCurrentInstance().getViewRoot().unsubscribeFromViewEvent(PreDestroyViewMapEvent.class, listener);
    if (httpSession != null) {
        synchronized (sessionToListeners) {
            if (sessionToListeners.containsKey(httpSession)) {
                sessionToListeners.get(httpSession).remove(listener);
            }
        }
    }
}

}

- ViewScopeViewMapListener:

public class ViewScopeViewMapListener implements ViewMapListener {

    private static final Log logger = LogFactory.getLog(ViewScope.class);

    private final String name;

    private final Runnable callback;

    private boolean callbackCalled = false;

    private final WeakReference<UIViewRoot> uiViewRootWeakReference;

    private final ViewScope viewScope;

    public ViewScopeViewMapListener(UIViewRoot root, String name, Runnable callback, ViewScope viewScope) {
        this.name = name;
        this.callback = callback;
        this.uiViewRootWeakReference = new WeakReference<>(root);
        this.viewScope = viewScope;
    }

    public synchronized void doCallback() {
        logger.trace("Going call callback for bean " + name);
        if (!callbackCalled) {
            try {
                callback.run();
            } finally {
                callbackCalled = true;
            }
        }
    }

    public String getName() {
        return name;
    }

    @Override
    public boolean isListenerForSource(Object source) {
        return (source == uiViewRootWeakReference.get());
    }

    @Override
    public void processEvent(SystemEvent event) throws AbortProcessingException {
        if (event instanceof PreDestroyViewMapEvent) {
            logger.trace("Going call callback for bean " + name);
            doCallback();
            viewScope.unregisterListener(this);
        }
    }

}

- SpringScopeView annotation:

@Qualifier
@Scope("view")
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface SpringScopeView {
}

- Define the custom scope:

    @Configuration
public class MyViewScope extends CustomScopeConfigurer {

    public InitViewScope() {
        log.info("Init ViewScope");
        Map<String, Object> map = new HashMap<>();
        map.put("view", new ViewScope());
        super.setScopes(map);
    }
}

- View scope bean sample:

@Component("employeeRequest")
@SpringScopeView
public class EmployeeRequestBean implements Serializable {

    private static final long serialVersionUID = 6609775672949354713L;

    

    @Autowired
    private CurrentUserBean currentUserBean;

    @Autowired
    private RequestRepository requestRepository;

    @Autowired
    private ActionRepository actionRepository;

    
    @Autowired
    private SMSServiceClient smsServiceClient;

    private List<AttachmentDTO> uploadedFilesList = new ArrayList<AttachmentDTO>();

    private Request request;
    
    private Action action;


    @PostConstruct
    public void init() {
        try {
            String selectedRequestId = FacesContext.getCurrentInstance().getExternalContext().getRequestParameterMap()
                    .get("selectedRequestId");
            if (StringUtils.isBlank(selectedRequestId))
                return;
            request = requestRepository.getOne(Long.parseLong(selectedRequestId));
            showRequest();
        } catch (Exception e) {
            log.error("Exception in init EmployeeRequestBean: ", e);
            throw new RuntimeException(e);
        }
    }

    @PreDestroy
    public void preDestroy() {
        System.err.println("####### EmployeeRequestBean DESTROYED #########");
    }
    

}

ISSUE: when performing logout all session scope beans get destroyed and a call to @PreDestroy is performed, while view scope beans @PreDestroy are not getting called!

this issue happens on WebSphere 8.5.5.13 only, but when running the same application on tomcat 9, everything works as expected.

Answer 1

@PreDestroy is tricky. Have you see this issue? They say that eventually, at some point it should be triggered. I assume, that it is not ok for you.

What to do?

Avoid @PreDestroy , I'm doing my best not to use them. I hate problems like this - something, sometimes is triggered, even if it works today, upgrade can break it...

Usually, what I do is to track sessions that are up, and running. Everything else can be closed - by calling method. That way I have tests, integration tests, also I can track number of active users. As usual - more work, better control.

To me that goes separately JSF, and Spring. That @PreDestroy is Spring feature. My guess is that something keeps reference to the object, and that is why it is not destroyed. And that jneat is separate from that. Prove here is that for pure Spring beans it works...