Creating a web service for use in an internal application and exposing it to others

For my web application, I am thinking about using the Spring framework. Initially, I was thinking of having different actions like create user or login, but now I have to expose some functionality to other applications. Should I create a web service that I call from my application and others do as well, or create an action from Spring and then just have others call the web service? It seems like I should minimize the different ways to call something, but does it make sense to call a web service that is running on the same application server as my main app? Would this be a bad idea from a performance stand point?

Update

I was concerned that Tomcat wouldn't be able to serve both the static or dynamic pages on port 80 (so users could go to www.example.com/welcome.jsp instead of www.example.com:8080/welcome.jsp), as well as a web service but I guess it doesn't matter as both are just served as requests from Tomcat. I'm guessing this means I'll have to change Tomcat to run on port 80 and other applications will have access the web service via this port. Or I could leave Tomcat running on port 8080 and put Apache in front on Tomcat on port 80 and Apache will serve the requests to Tomc开发者_如何转开发at. Is that correct?

I'd put the common business logic in a "business service" and :

1. call it from an action in your web app
2. expose it as a web service for other applications

To me, there is nothing bad with this approach and it's pretty easy and clean to implement it with Spring. Actually, I would find ugly to expose this business service as web service only and to call it from the web app (and I'm pretty sure that this will be more complicated to implement on the web app side). You have different "usage contexts", just expose the adequate interface for them.

(EDIT: I'm answering a question of the OP posted as comment below)

You can deploy the web application and the web service in the same WAR (but this is just a deployment choice, you could package the business logic in a JAR and use it in several WARs). Regarding the port, I'm not sure to understand your question. Traditionally, you'll use a web server (e.g. apache) in front of your application server. If you don't, you can always choose to run you app server on port 80. Actually, in both case you are free to use whatever port you want. Using port 80 is just convenient.

Yes, your update is correct.