{"id":277,"date":"2017-02-18T19:00:44","date_gmt":"2017-02-18T18:00:44","guid":{"rendered":"https:\/\/www.nikostotz.de\/blog\/?p=277"},"modified":"2017-02-22T22:12:10","modified_gmt":"2017-02-22T21:12:10","slug":"combine-xcore-xtend-ecore-and-maven","status":"publish","type":"post","link":"https:\/\/www.nikostotz.de\/blog\/combine-xcore-xtend-ecore-and-maven\/","title":{"rendered":"Combine Xcore, Xtend, Ecore, and Maven"},"content":{"rendered":"

Update:<\/b> Christian found a workaround for compiling code that references Ecore types. We adjusted the article.<\/p>\n

Lots of thanks to Christian<\/a> for figuring this out together.<\/p>\n

The complete example is available on github.<\/a><\/p>\n

Also, we included all the files as Listings at the end of the article.<\/a> They are heavily commented.<\/p>\n

Objective<\/h1>\n

Inside an Eclipse plugin, we have EMF models defined in both Xcore and Ecore, using types from each other. Also, we have a Helper Xtend class that’s called from Xcore and uses types from the same model. We want to build the Eclipse Plugin with Maven. We also don’t want to commit any generated sources (from Xtend, Xcore, or Ecore).<\/p>\n

Issue<\/h1>\n

Usually, we would use xtend-maven-plugin<\/tt> to build the Xtend classes, xtext-maven-plugin<\/tt> to build the Xcore model, and MWE2<\/tt> to build the Ecore model.<\/p>\n

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However, we have a cyclic compile-time dependency between AllGreetings<\/tt> calling GreetingsHelper.compileAllGreetings()<\/tt> which receives a parameter of type AllGreetings<\/tt>. We also have a cyclic dependency between AllGreetings<\/tt> calling GreetingsHelper.compileAllPersons()<\/tt> and using IPerson<\/tt> type.<\/p>\n

Solution<\/h1>\n

Java (and Xtend) can solve such cycles in general, but only if they process all members at the same time. Thus, we need to make sure both Xtend and Xcore are generated within the same Maven plugin.<\/p>\n

We didn’t find a way to include the regular Ecore generator in the same step, so we keep this in a separate MWE2-based Maven plugin.<\/p>\n

For generating persons.ecore<\/a>, we call an MWE2 workflow from Maven via exec-maven-plugin<\/tt>. The workflow<\/a> itself gets a bit more complicated, as we use INamedElement<\/tt> from base.xcore<\/a> as a supertype to IPerson<\/tt> inside persons.ecore<\/a>. Thus, we need to ensure that base.xcore<\/a> is loaded, available, and can be understood by the Ecore generator.<\/p>\n

Afterwards, we use xtext-maven-plugin<\/tt> to generate both Xtend<\/a> and the two<\/a> Xcore<\/a> models. To do this, we need to include all the required languages and dependencies into one single plugin in our maven pom<\/a>.<\/p>\n

The first version could not compile GreetingsHelper.compileAllPersons()<\/a> because it referenced types from persons.ecore<\/a>, and these could not be resolved by the EMF validator. As a workaround, we disabled the validator in the workflow<\/a>.<\/p>\n

Remarks<\/h1>\n