#78 Added functionality for accessing the current ModelInstanceRepository implementation outside of the GenerationContext

fermenter-mda/src/main/java/org/technologybrewery/fermenter/mda/metamodel/ModelInstanceRepositoryManager.java

@@ -10,19 +10,43 @@ public final class ModelInstanceRepositoryManager {
 
     private static ThreadLocal<Map<String, Object>> threadBoundInstance = ThreadLocal.withInitial(HashMap::new);
 
+    private static final String ABSTRACT_MODEL_INSTANCE_REPOSITORY_CLASS_NAME = 
+                                "org.technologybrewery.fermenter.mda.metamodel.AbstractModelInstanceRepository";
+
     private ModelInstanceRepositoryManager() {
         // prevent private instantiation of all static class
     }
 
     /**
-     * Adds a repository. Only one repository of each type will be kept.
+     * Sets a repository as the repository implementation for its own class and any super 
+     * classes if present. This enables downstream projects to safely extend upstream 
+     * {@link ModelInstanceRepository}'s without breaking existing calls to getRepository().
+     * 
+     * For example, given the classes:
+     *  MIR_A implements AbstractModelInstanceRepository
+     *  MIR_B extends MIR_A
+     *  MIR_C extends MIR_B
+     * 
+     * When the repository is set using setRepository(MIR_C). Then following calls to 
+     * getRepository would all return the MIR_C instance:
+     *  getMetamodelRepository(MIR_A.class) -> MIR_C
+     *  getMetamodelRepository(MIR_B.class) -> MIR_C
+     *  getMetamodelRepository(MIR_C.class) -> MIR_C
      * 
-     * @param respository
+     * @param repository
      *            repository to add
      */
-    public static void setRepository(ModelInstanceRepository respository) {
+    public static void setRepository(ModelInstanceRepository repository) {
         Map<String, Object> instanceMap = threadBoundInstance.get();
-        instanceMap.put(respository.getClass().toString(), respository);
+
+        instanceMap.put(repository.getClass().toString(), repository);
+        Class<?> repositorySuperClass = repository.getClass().getSuperclass();
+
+        // Add an entry for all superclasses of the repository
+        while (!repositorySuperClass.getName().equals(ABSTRACT_MODEL_INSTANCE_REPOSITORY_CLASS_NAME)) {
+            instanceMap.put(repositorySuperClass.toString(), repository);
+            repositorySuperClass = repositorySuperClass.getSuperclass();
+        }
     }
 
     /**

fermenter-mda/src/test/java/org/technologybrewery/fermenter/mda/metamodel/MetadataRepositoryManagerTest.java

@@ -61,6 +61,27 @@ public void testOverwriteMetadataReposistory() {
 
     }
 
+    @Test
+    public void testMetadataRepositoryExtension() {
+        // Set the repository to the lowest subclass
+        TestMetadataRepository testRepositoryExtensionB = new TestMetadataRepositoryExtensionB(null);
+        ModelInstanceRepositoryManager.setRepository(testRepositoryExtensionB);
+
+        // Get the repository extension with its superclass references
+        TestMetadataRepository managedTestRespository = ModelInstanceRepositoryManager
+                .getMetamodelRepository(TestMetadataRepository.class);
+        assertEquals(testRepositoryExtensionB, managedTestRespository);
+
+        managedTestRespository = ModelInstanceRepositoryManager
+                .getMetamodelRepository(TestMetadataRepositoryExtensionA.class);
+        assertEquals(testRepositoryExtensionB, managedTestRespository);
+
+        // Get the repository extension with its current class reference
+        managedTestRespository = ModelInstanceRepositoryManager
+                .getMetamodelRepository(TestMetadataRepositoryExtensionB.class);
+        assertEquals(testRepositoryExtensionB, managedTestRespository);
+    }
+
     @Test
     public void testClearMetadataReposistoryManager() {
         setNewDefaultMetadataRepository();
@@ -106,3 +127,21 @@ public void validate() {
     }
 
 }
+
+/**
+ * Used for testing only.
+ */
+class TestMetadataRepositoryExtensionA extends TestMetadataRepository {
+    public TestMetadataRepositoryExtensionA(ModelRepositoryConfiguration config) {
+        super(config);
+    }
+}
+
+/**
+ * Used for testing only.
+ */
+class TestMetadataRepositoryExtensionB extends TestMetadataRepositoryExtensionA {
+    public TestMetadataRepositoryExtensionB(ModelRepositoryConfiguration config) {
+        super(config);
+    }
+}