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I have a Java EE based REST api application. It has a layered architecture like the following:

  1. Resources (Jax-rs resources)
    • Object Validation
    • Object Mapper
  2. Service Layer
  3. Repository Layer
  4. JPA Entities

Everything is wired using Spring dependency injection.

I need to design this core application in such a way that it allows other external developers to write extensions/plugins and override or extends any minor or major functionality in the core. Think of it like Wordpress CMS in Java EE if that helps. How would you design a plugin system around the current architecture?

One obvious way that I can think of is override or add new functionality to the proper resource (with validation, objectmapper), service, repository and entity and create a jar + xml out of it. But I want to make sure that the plugin developer has to write the absolutely minimum amount of code to get the new functionality working, while reusing mush of the core code.

Assume, you want to create a wordpress blog post extension that lets you create blog posts with few extra fields that don't exist in core yet. What would be the simplest and cleanest way to go about designing the current Java EE app, so its easy for the plugin/extension developers? Any patterns that could be useful like strategy or template method pattern?

Are there any open source Java CMS that follow the model using Spring/JPA and standard technologies?

quantumSoup
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Langali
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1 Answers1

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I think you mean to extend the functionality, rather than override the core. Typical architecture examples define concerns which can be overridden (separate from core) and make provisions. Eclipse framework achieves this using a combination of plugin-extensions & extension-points mechanism. This is taken further using OSGI bundling.

Another alternative is to breakdown the application into smaller independent modules/services. All you need to do is host these modules over an ESB/Application Integrator (like Mule/Spring Integration) and allow users to configure their version of routing/transformation. Extension would mean creation of new transformers which get added to the message flow.

questzen
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