I have a large scale project I am working on at the moment using Eclipse. Normally, as a one man team, these problems would not be an issue, but as our team is not one person we need to be able to break up pieces of the project to be worked on by certain team members.
In simplicity, let's say I have two layers to be separated apart: 1. Each DAO is a separate Java project, to be worked upon individually 2. The web-tier service layer contains all of our service endpoints and must be able to reference all of the DAOs. This layer runs on Tomcat as a dynamic web project, and utilizes Adobe LiveCycle Data Services as the piece that handles creation and management of endpoints.
Now, the issue we are running into is that when we create a DAO and unit test it individually it runs great. But when we reference it into our service project and try to run it we begin to get all kinds of issues related to the fact that we have two different versions of certain jars referenced in and as such we begin to have errors when running the server.
As a result, we know we can solve the issue by pulling the problem jars and ensuring that this is not an issue again in the future, but as I said before this is a large scale project with multiple people working on it and we don't want to be spending our time weeding out dependency issues when under the gun.
We are looking for recommendations on where to proceed for alternative solutions? Our team is new to JavaEE and as such we don't have much of a bearing on what we can use to tie everything together in it, or if it is a viable solution. Should we be looking at turning our DAOs into EJBs and deploying them in an EAR library? If so, where would our service layer lie, and would the service layer be able to reference the DAO classes since the EJB maintains it's own classpath (from what we have read?) Are we looking down the wrong path, or are we completely wrong in our current understanding of JavaEE?
Any assistance is greatly appreciated. We are still in the framework stage of this project and we want to be sure that we will be able to maintain it in the long run.
If you can run all the sub-components using the same set of dependencies, you may find it helpful to migrate to a Maven build.
With Maven, you can define a top-level project that manages all the 3rd party dependency versions in one place, so all modules are built, tested and deployed against the same library versions. You are also likely to find Maven a good fit for the multi-module approach you have adopted, as it ensures that a project is rebuilt correctly if one of its dependencies changes.
You would still be able to use dynamic web projects as before; Eclipse will automatically deploy the DAOs as part of the service project (IIRC you need to characterise the DAOs as utility modules).
If you do go down the EJB root, you are correct that each EAR will get its own class-loader, and can therefore use a varying set of dependencies. However, in your position I would tend to look at improving your dependency management first - it'll probably be cheaper and easier.