DATACMNS-374 - Improved error handling in case of a missing repository.

In Repositories.getCrudInvoker(…) we now throw an IllegalArgumentException if we cannot find an appropriate repository for the given domain class. Previously it just blew up with a NullPointerException without a clear error message.

Original pull request: #46.

src/main/java/org/springframework/data/repository/support/Repositories.java

@@ -163,6 +163,8 @@ public class Repositories implements Iterable<Class<?>> {
 		RepositoryInformation information = getRepositoryInformationFor(domainClass);
 		Object repository = getRepositoryFor(domainClass);
 
+		Assert.notNull(repository, String.format("No repository found for domain class: %s", domainClass));
+
 		if (repository instanceof CrudRepository) {
 			return new CrudRepositoryInvoker<T>((CrudRepository<T, Serializable>) repository);
 		} else {

src/test/java/org/springframework/data/repository/support/RepositoriesUnitTests.java

@@ -25,7 +25,9 @@ import java.util.Collections;
 import java.util.List;
 
 import org.junit.Before;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 import org.junit.runner.RunWith;
 import org.mockito.runners.MockitoJUnitRunner;
 import org.springframework.beans.factory.support.AbstractBeanDefinition;
@@ -51,12 +53,15 @@ import org.springframework.data.repository.query.QueryMethod;
  * Unit tests for {@link Repositories}.
  * 
  * @author Oliver Gierke
+ * @author Thomas Darimont
  */
 @RunWith(MockitoJUnitRunner.class)
 public class RepositoriesUnitTests {
 
 	ApplicationContext context;
 
+	@Rule public ExpectedException exception = ExpectedException.none();
+
 	@Before
 	public void setUp() {
 
@@ -107,6 +112,19 @@ public class RepositoriesUnitTests {
 		assertThat(repositories.getPersistentEntity(Address.class), is(notNullValue()));
 	}
 
+	/**
+	 * @see DATACMNS-374
+	 */
+	@Test
+	public void shouldThrowMeaningfulExceptionWhenTheRepositoryForAGivenDomainClassCannotBeFound() {
+
+		exception.expect(IllegalArgumentException.class);
+		exception.expectMessage(containsString("No repository found for domain class: "));
+
+		Repositories repositories = new Repositories(context);
+		repositories.getCrudInvoker(EntityWithoutRepository.class);
+	}
+
 	class Person {
 
 	}
@@ -115,6 +133,10 @@ public class RepositoriesUnitTests {
 
 	}
 
+	class EntityWithoutRepository {
+
+	}
+
 	interface PersonRepository extends CrudRepository<Person, Long> {
 
 	}