Learning the basics of the Eclipse Modeling Framework (EMF).

The EMF project is a modeling framework and code generation facility for building tools and other applications based on a structured data model. From a model specification described in XMI, EMF provides tools and runtime support to produce a set of Java classes for the model, along with a set of adapter classes that enable viewing and command-based editing of the model, and a basic editor.

https://eclipse.org/modeling/emf/

Learning goals

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of this step-by-step guideline and exercise:

• Learn how to generate code using EMF.
• Understand how to use containment / container and regular relations in EMF.
• Learn how to instantiate your models in EMF and by Java code.

Prerequisites

• You need Eclipse Modeling Tools. Installation guidelines.

Part #1: Modelling a library.

To get a modelling kickstart, we will start using an existing domain model from a library. This model consists of the following main concepts:

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1. Go into "File > New > Example... > Eclipse Modeling Framework > Extended Library Model Example"
2. Select "org.eclipse.emf.examples.library" and press "Finish".
3. Double click on the extlibrary.ecore file, and you will see an editor with a hierarchical breakdown of the domain model.
   
   
   
   
   

Part #2: Concepts and Relations

1. Find examples of EClasses and EDataTypes
2. Find examples of containment / container and ordinary relations in the model.
3. Try to find features properties such as:
   1. multiplicity – lower and upper bound
   2. changeable – allows being set (using setter)
   3. derived – computed from other values 
   4. transient – should not be stored in external resource
   5. volatile – should not need to be stored in memory
   6. order – not used in practice, but good to know if order is important

Part #3: Extending the model

Use the model editor to add a new BookCategory. Hint: right-click on BookCategory > New Child... > Select EEnum Literal

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Remember to save our ecore file, after the new category is added.

Part #4: Generating Java Code

First we want to validate our ecore model.

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By double clicking on the BookCategory.java file you see a enum implementation where Computer Science (the modification we made to the domain model) is added as a literal object:

Part #5 Instantiating from Java

Now, with Java code for our domain model automatically generated, it is time to learn how to use and instantiate the model.

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Note how you use the EXTLibraryFactory.eINSTANCE to create java objects.

Part #6 Instantiating from an Editor

With the ecore model we have for the library domain, we can also use EMF to generate an editor that we can use for instantiation.

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