Share object between JavaEE applications on the same JVM (using JNDI)

Question

I'm running a JBoss AS 7.1.3.Final installation with a lot of applications. One of those applications provides common resources and functionallities used by all applications (let's call it framework). I'm also planning to move to WildFly 8, if this is an useful information for your answer.

All applications should only be accessible, if the framework is available (up and running). My current implementation to achive this dependency is not that nice** and as I'm currently re-designing some parts of the environment, I'm looking for a much neater solution for it. My first idea was to create some kind of a manager which will be instantiated by the application server and is available to all applications. So after an application is started, it could register itself on the manager and as soon as the framework is up, the applications will be notified.

Is this possible using the JNDI of the JVM where all applications + framework are running? How must this be implemented? It's really hard to find useful information about how the JNDI works and what is possible with it. Do you have any other, simplier ideas, how to share a class instance between applications?

Thank you.

** Currently I'm using a EJB-timer in the applications and a singleton EJB in the framework. The framework is available as soon as the EJB lookup succeeds.

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Edit #1 Some more informations as requested by Nikos Paraskevopoulos

• One functionionality that is provided by the framework is the maintenance mode. The applications will check, right after startup, if it is blocked for normal users. It will also receive notifications about planned maintenances. (central DB, the application has no rights on it)
• Common stylesheets or layouts are deployed with the framework.
• The user informations are provided by the framework. (central DB, the application has no rights on it)

The main problem is: How could I avoid any timers? I have no idea, how I could ensure, that the framework is up before everything else.

Answer 1

A few thoughts:

• JBoss has the capability of ordering deployments according to their dependencies. See here and here. So, if all the "applications" depend explicitly on the "framework", your problem may be solved.

• It seems you have a quite strongly coupled configuration. Would it be possible to decouple them, e.g. provide the service through web services (SOAP/REST)? Of course this introduces extra overhead for the communication and the refactoring...

• JNDI can be seen (very roughly) as a name to object map shared across the applications. As such, you may share stuff through it. But I do not see how will you solve the timing problem, i.e. wait for a service to be available before using it from the "applications". The manager component you mention can be placed in JNDI.

This is not a complete answer, but it would not fit as a comment either. Maybe if you presented more details on the nature of the applications, the frameworks used etc, you could get more specific answers.

Good luck anyway

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Edit #1:

• Maintenance mode: This may be nice for using with JNDI. A servlet filter that intercepts every (applicable) request will check a global JNDI name; if it is not found (i.e. framework not started) or it is false, it will short-circuit the processing of the request, sending back the "maintenance mode" page. The framework will have to set a Boolean in the global JNDI name as soon as it has started and maintain its value, i.e. set it to false if maintenance mode is active.

• Common stylesheets: This is really covered by the maintenance mode flag, I believe. Layouts: It depends on the view technology/layouts technology.

• User information: This is a good candidate for SOAP/REST implementation. It is not expected to be called frequently, so I assume overhead will not matter.

Answer 2

I think OSGi is the technology you should consider. Basically you have an OSGi container with applications (called bundles) which provide or consume services. So you would have a framework service which is consumed by all applications. JBoss is an OSGi container, as far as I know.