DATAMONGO-1437 - Preserve non translatable Exception cause when lazily resolving DBRef.

We now preserve the cause of Exceptions that cannot be translated into DataAccessExceptions when an error occurs during lazily loading DBRefs.

Original pull request: #367.

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/DefaultDbRefResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2015 the original author or authors.
+ * Copyright 2013-2016 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -180,8 +180,8 @@ public class DefaultDbRefResolver implements DbRefResolver {
 	 * @author Oliver Gierke
 	 * @author Christoph Strobl
 	 */
-	static class LazyLoadingInterceptor implements MethodInterceptor, org.springframework.cglib.proxy.MethodInterceptor,
-			Serializable {
+	static class LazyLoadingInterceptor
+			implements MethodInterceptor, org.springframework.cglib.proxy.MethodInterceptor, Serializable {
 
 		private static final Method INITIALIZE_METHOD, TO_DBREF_METHOD, FINALIZE_METHOD;
 
@@ -387,7 +387,8 @@ public class DefaultDbRefResolver implements DbRefResolver {
 				} catch (RuntimeException ex) {
 
 					DataAccessException translatedException = this.exceptionTranslator.translateExceptionIfPossible(ex);
-					throw new LazyLoadingException("Unable to lazily resolve DBRef!", translatedException);
+					throw new LazyLoadingException("Unable to lazily resolve DBRef!",
+							translatedException != null ? translatedException : ex);
 				}
 			}
 

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/LazyLoadingInterceptorUntiTests.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.convert;
+
+import static org.hamcrest.core.Is.*;
+import static org.hamcrest.core.IsEqual.*;
+import static org.mockito.Mockito.*;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.runners.MockitoJUnitRunner;
+import org.springframework.dao.DataAccessException;
+import org.springframework.dao.support.PersistenceExceptionTranslator;
+import org.springframework.data.mongodb.LazyLoadingException;
+import org.springframework.data.mongodb.core.convert.DefaultDbRefResolver.LazyLoadingInterceptor;
+import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
+
+import com.mongodb.DBRef;
+
+@RunWith(MockitoJUnitRunner.class)
+public class LazyLoadingInterceptorUntiTests {
+
+	public @Rule ExpectedException exception = ExpectedException.none();
+
+	@Mock MongoPersistentProperty propertyMock;
+	@Mock DBRef dbrefMock;
+	@Mock DbRefResolverCallback callbackMock;
+
+	/**
+	 * @see DATAMONGO-1437
+	 */
+	@Test
+	public void shouldPreserveCauseForNonTranslatableExceptions()
+			throws NoSuchMethodException, SecurityException, Throwable {
+
+		NullPointerException npe = new NullPointerException("Some Exception we did not think about.");
+		when(callbackMock.resolve(propertyMock)).thenThrow(npe);
+
+		exception.expect(LazyLoadingException.class);
+		exception.expectCause(is(equalTo(npe)));
+
+		new LazyLoadingInterceptor(propertyMock, dbrefMock, new NullExceptionTranslator(), callbackMock).intercept(null,
+				LazyLoadingProxy.class.getMethod("getTarget"), null, null);
+	}
+
+	static class NullExceptionTranslator implements PersistenceExceptionTranslator {
+
+		@Override
+		public DataAccessException translateExceptionIfPossible(RuntimeException ex) {
+			return null;
+		}
+	}
+}