DATAMONGO-461 - Fixed potential NullPointerException in MappedConstructor.

Reject PersistentEntity instances that don't have a PersistenceConstructor as this indicates a mapping problem (either a constructor needed to be annotated or a custom converter registered).

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

@@ -18,6 +18,7 @@ package org.springframework.data.mongodb.core.convert;
 import java.util.HashSet;
 import java.util.Set;
 
+import org.springframework.data.annotation.PersistenceConstructor;
 import org.springframework.data.mapping.PersistentEntity;
 import org.springframework.data.mapping.PersistentProperty;
 import org.springframework.data.mapping.PreferredConstructor;
@@ -25,6 +26,7 @@ import org.springframework.data.mapping.PreferredConstructor.Parameter;
 import org.springframework.data.mapping.PropertyPath;
 import org.springframework.data.mapping.context.MappingContext;
 import org.springframework.data.mapping.context.PersistentPropertyPath;
+import org.springframework.data.mapping.model.MappingException;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
 import org.springframework.data.util.TypeInformation;
@@ -37,6 +39,9 @@ import org.springframework.util.Assert;
  */
 class MappedConstructor {
 
+	private static final String REJECT_CONSTRUCTOR = String.format("Entity doesn't have a usable constructor, either "
+			+ "provide a custom converter or annotate a constructor with @%s!", PersistenceConstructor.class.getSimpleName());
+
 	private final Set<MappedConstructor.MappedParameter> parameters;
 
 	/**
@@ -44,13 +49,19 @@ class MappedConstructor {
 	 * 
 	 * @param entity must not be {@literal null}.
 	 * @param context must not be {@literal null}.
+	 * @throws MappingException in case the {@link MongoPersistentEntity} handed in does not have a
+	 *           {@link PreferredConstructor}.
 	 */
 	public MappedConstructor(MongoPersistentEntity<?> entity,
-			MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> context) {
+			MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> context) throws MappingException {
 
 		Assert.notNull(entity);
 		Assert.notNull(context);
 
+		if (entity.getPreferredConstructor() == null) {
+			throw new MappingException(REJECT_CONSTRUCTOR);
+		}
+
 		this.parameters = new HashSet<MappedConstructor.MappedParameter>();
 
 		for (Parameter<?> parameter : entity.getPreferredConstructor().getParameters()) {
@@ -83,6 +94,7 @@ class MappedConstructor {
 	 * 
 	 * @param parameter must not be {@literal null}.
 	 * @return
+	 * @throws MappingException in case no {@link MappedParameter} can be found for the given {@link Parameter}.
 	 */
 	public MappedParameter getFor(Parameter<?> parameter) {
 
@@ -92,7 +104,7 @@ class MappedConstructor {
 			}
 		}
 
-		throw new IllegalStateException(String.format("Didn't find a MappedParameter for %s!", parameter.toString()));
+		throw new MappingException(String.format("Didn't find a MappedParameter for %s!", parameter.toString()));
 	}
 
 	/**
@@ -165,4 +177,4 @@ class MappedConstructor {
 			return this.property.equals(property);
 		}
 	}
-}
+}

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

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2012 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 org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.runners.MockitoJUnitRunner;
+import org.springframework.data.mapping.context.MappingContext;
+import org.springframework.data.mapping.model.MappingException;
+import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
+import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
+
+/**
+ * Unit tests for {@link MappedConstructor}.
+ * 
+ * @author Oliver Gierke
+ */
+@RunWith(MockitoJUnitRunner.class)
+public class MappedConstructorUnitTests {
+
+	@Mock
+	MongoPersistentEntity<?> entity;
+	@Mock
+	MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> mappingContext;
+
+	@Test(expected = MappingException.class)
+	public void rejectsEntityWithoutPersistenceConstructor() {
+		new MappedConstructor(entity, mappingContext);
+	}
+}