How to call EJB running on remote machine over internet from standalone client on another machine without JSP/Servlet as intermediate?

Question

Case: Developing a standalone java client which will run on different locations on multiple user desktops. Application server(Oracle Weblogic) will be running at centralized location in different place.

Now I want to access/call EJB (Session Bean) running on central server from client. As client and server are on different location and not connected via Intranet or LAN only medium of connection is internet.

My question is how can I call EJB's in server directly from client without using a servlet/JSP layer in between?

EJB was devised for remote access , why a servlet dependency?

I have read that RMI-IIOP can be used to make this type of connection but I am unable to use RMI-IIOP over internet!

What is the best architecture/solution for this type of remote communication?

Answer 1

The RMI/IIOP is the default provided by the application server. By configuration / annotation SOAP or HTTP/XML/JSON can be used instead. (Although these protocols have some trade-off with security, transactions, etc.)

Answer 2

Remember that the EJB is a consise unit of buisness logic, they are protocol agnostic. Exposing it to the caller is the job of the application server. RMI-IIOP/CORBA is just the default.

The internet routing issue with IIOP is similar to many protocols, it is not that they don't route over the internet, it is that they do not have an easy proxy / reverse proxy feature built in. Hence has issues going through a DMZ. Compared to HTTP which has support for reverse proxy, or SMTP allows for relaying. The firewall port is typically closed as well, You would not normally put an application server in a DMZ.

To solve the problem of giving direct access to business logic to an external network, i typically change protocols to something designed for external network communications. For example, annotate (or deployment descriptor) the EJBs with the @WebMethod and the become available as SOAP services automatically, or use the @PATH (etc.) to expose them as HTTP/JSON/XML services.

CORBA type protocols have out-of-the-box features for security, XA transactions and are very high performance. I usually use this for enterprise level component oriented systems internally. (each EJB component is essentially used as a microservice) While for external integration, especially where the caller does not need to pre-know the interface contract, I typically go with a SOAP or HTTP/JSON/XML endpoints for the EJB.

Answer 3

Well EJB doesn't have at all a dependency on the servlet. They can be called directly using RMI/IIOP. The only problem you have to face is the network structure, i mean RMI/IIOP uses some ports that usually aren't open in company Firewall and it could be quite difficult to open them. So usually it is better to make an HTTP request because almost all firewall accepts this kind of request.

So if you are in an intranet (client and server in the same intranet) you can use RMI/IIOP but if your client and server are placed in different networks with internet connection then i suggest to you to use HTTP. You could use Webservices and "export" your EJB as a web service. If you don't want to use Webservices then you could implement as extrema-ratio a servlet that receives HTTP request and calls the EJB. It depends on the type of object you have to return to the client. If it is a simple string or something not too complex then you could even use a Servlet but if they are objects then the Servelt solution isn't the right choice.

Answer 4

There is no servlet dependency. There is a custom client/protocol dependency that's app server specific. Each server has their own way of setting up the connection, manifested through configuring JNDI for the proper providers and protocol handlers.

Why won't RMI-IIOP work over the internet? The only potential issue I can see there is security, I don't know if there's an encrypted version of RMI-IIOP or not, but other than that, it's a perfectly routable protocol.

You may run in to port and firewall issues, but that's not the protocols fault. If you want to run RMI-IIOP over port 80 (http's port), then that's fine (obviously it won't be http, nor work with http proxies, but again, that's not the protocols issue).

Weblogic also has (had?) their own protocol, T3? I think it was? Can you use that?

I think the key is why you don't think you can run RMI-IIOP "over the internet", and trying to solve that problem, not necessarily what protocol to use.