As described in Benefits of Liferay 7 for Liferay 6 Developers, applications that comprise OSGi modules offer considerable advantages over monolithic applications.
The main benefit is that modular development practices structure code in ways that reduce maintenance costs. These practices involve, for example, defining contracts (such as APIs) more clearly, hiding internal classes, and handling dependencies more carefully. Related to this, module dependencies are explicitly listed within a module. Modules run only when all their dependencies are met–this can eliminate many obscure run time errors.
Splitting large applications into small independent modules lets you focus on smaller release cycles for those modules. Individual modules can be updated independently of the others. For instance, you might fix a JSP’s security issue in an application’s web (client) module. The issue only affects that module–none of the application’s other modules need change.
The scenarios described below can help you decide whether to convert an application to modules.
When not to convert?
- You have a portlet that’s JSR-168/286 compatible and you still want to be able to deploy it to another portlet container. In this case, it’s best to stay with the traditional WAR model. (To eliminate this reason for not converting, Liferay is discussing with other vendors the possibility of making modular portlets a standard.)
- You’re using a complex web framework that is heavily tied to the Java EE programming model and the amount of effort necessary to make it work with OSGi is more than you feel is necessary or warranted.
- You want to minimize effort to get your application to working on Liferay Portal CE 7.0.
When to convert?
- You have a very large application with many lines of code. If you’ve got lots of developers making changes, separating the code into modules can make it easier and faster to get releases out.
- Your application has reusable parts that you want to consume outside of it. For instance, you have business logic that you’re reusing in different projects. Modules let you consume their services from other modules.
- In general, you want to start reaping the benefits of modular development.
You can now make an informed decision on whether to stick with your upgraded traditional application as is or modularize it to leverage Liferay Portal CE 7.0’s modularity features.