Sano J Sano J - 1 month ago 22
Java Question

Modular java ee application

I need to refactor a Java EE application because the current design isn't very modular, in fact it is quite a mess. There is a Business Facade but as the application has been developed by several people and therefore the original design has been ignored several times. The application is currently running on tomcat with JSF but it will be ported to websphere soon. I already did some research about different design patterns to encapsulate the business logic from the view and also how to make the application modular so that it will be easy to put more functionality to it because the application will be enhanced in the future . I've read about OSGI but I think that would be an overkill.

The application is already split into layers. But I'm far away of defining API's. I've already cleaned up the application a bit. Now all the beans access the business logic through the business facade methods. But the business facade consists of about 40 methods which I think isn't very nice.

3rd party edit

For example I have these model classes


  • ManageLdap
    with methods like
    createAccount
    and
    deleteAccount

  • GroupManager
    which manages the ldap groups



In the business facade I have a method
createAccount
which


  • calls the
    ManagerLdap
    class to create an ldap account and

  • does some logging and also

  • calls
    GroupManager



This pseudo code

package Model.ManageLdap

public class ManageLdap
{
public ldapAccount createAccount() { }

public ldapAccount deleteAccount() { }
}

public class GroupManager
{
public bool addAccountToGroup(var account) { }
}


And in the business facade

package BusinessFacade.Foo

public class SomeFoo
{
public ldapAccount createAccount()
{
var ldapAccount = new ManageLdap.createAccount();
Logger.log("Account created");
var accountWasAdded = GroupManager.addAccountToGroup(ldapAccount);
}
}


Now if I want to put additional functionality to the application like the option to create a subversion repository for a user


  • i have to implement a model class to create repos,

  • put some methods in the business facade and

  • create an additional bean to be accessed by the view.



That makes the facade even bigger and confusing but beside that, this isn't what I call a modular design.

So how can I seperate the business logic from the view without having a huge business facade?

Answer

For first try to split your application into several layers like:

  • DAO
  • Sevices
  • Security
  • View
  • Etc.

Then extract some API from each of layer (like dao-api, service-api and so on. Each of api modules should have a set of interfaces).

Then create a set of modules (like service-api, service-impl, dao-api, dao-impl) and involve some building tool (gradle or maven) to manage them.

Do not allow one implementation module to have dependency to another implementation module (only impl -> api or api -> api).

Each module - separated jar file.

After such refactoring it will be much harder to break application design in future.