Using black box implementations in Eclipse QVTo

In QVT, it is possible to execute external code in a transformation. According to the standard, it has some benefits (QVT, 2009, p.10):

• It allows complex algorithms to be coded in any programming language with a MOF binding (or that can be executed from a language with a MOF binding).
• It allows the use of domain specific libraries to calculate model property values. For example, mathematical, engineering, bioscience and many other domains have large libraries that encode domain-specific algorithms which will difficult, if not impossible to express using OCL.
• It allows implementations of some parts of a transformation to be opaque.

The external code is called a “black box implementation”.

Using this concept, in Eclipse QVTo it is possible to execute an external Java code. In this post I will describe how you can easily create a black box implementation to execute a math sine operation.

1. You must create a plug-in that contains the black box implementation. The easiest way to do it is to use the existing example. In eclipse, select “File->New->Example” and choose “Black Box Library Definition”. Click Finish. You will see a new Project called “org.eclipse.m2m.qvt.oml.examples.blackbox”.
2. Open the project and edit the class “UtilitiesLibrary”. Add a new method:

   public static double sin (double value) {
       return Math.sin(value);
   }

   That’s it. You’ve created your black box operation.

3. Now you have to create a new plug-in. There are two options to do this:
   1. If you want just to test, you can open a new eclipse instance considering the existing code by selecting the file “plugin.xml” and right clicking “Run As->Eclipse Application”. It will open a new instance of eclipse with your plug-in available.
   2. The other option is to actually create the plug-in. To do so, open “plugin.xml” and select “Export Wizard” in its “Export” section in the “Overview tab”. Select the corresponding plug-in (org.eclipse.m2m.qvt.oml.examples.blackbox (1.0.0)). Copy the jar file (org.eclipse.m2m.qvt.oml.examples.blackbox_1.0.0.jar) to the “plugins” folder of eclipse and restart eclipse.
4. Now, the black box implementation is available. Just create a new “Operational QVT Project” (in “New->Project”). Create a new transformation (right click the transforms folder and select “New->Other” and “Operational QVT Transformation”). Write the following code:

   import m2m.qvt.oml.ExampleJavaLib;
   
   transformation Test();
   
   main() {
       log(sin(2).toString())
   }

   An run the transformation. It will present the result of “sin(2)” in the console. The magic is to import the package “m2m.qvt.oml.ExampleJavaLib” (this name is defined in the “plugin.xml” in “” – just change it to have a different name).

I used the Eclipse Helio version, but it should work in the newer version of eclipse.

Obs: depending on your Eclipse configuration, this error appear while generating the plug-in:

D:.metadata.pluginsorg.eclipse.pde.coretemp
org.eclipse.pde.container.feature
assemble.org.eclipse.pde.container.feature.win32.win32.x86.xml:88:
The following error occurred while executing this line:
D:.metadata.pluginsorg.eclipse.pde.coretemp
org.eclipse.pde.container.feature
assemble.org.eclipse.pde.container.feature.win32.win32.x86.xml:103:
The following error occurred while executing this line:
D:.metadata.pluginsorg.eclipse.pde.coretemp
org.eclipse.pde.container.feature
assemble.org.eclipse.pde.container.feature.win32.win32.x86.xml:26:
The following error occurred while executing this line:
D:\org.eclipse.m2m.qvt.oml.examples.blackboxbuild.xml:214:
The following error occurred while executing this line:
C:org.eclipse.m2m.qvt.oml.examples.blackboxbuild.xml:289:
Problem: failed to create task or type apitooling.apigeneration
Cause: The name is undefined.
Action: Check the spelling.
Action: Check that any custom tasks/types have been declared.
Action: Check that any/ declarations have taken place.

This seems to happen because the plugin “org.eclipse.pde.api.tools” is not available… Just go “Help->Install New Software” and download “Eclipse Plug-in Development Environment”.