DATACMNS-1177 - Parameter.isDynamicProjectionParameter() uses unwrapped type instead of actual type.

When trying to determine if a parameter is a dynamic projection parameter, i.e. the parameter of type Class that determines the projection to use, now the type parameter of that method parameter gets compared with the unwrapped return type. Therefore this works now not only for Maps and Collections but also for the various wrappers defined in QueryExecutionConverters.

Moved the method for unwrapping the return type from AbstractRepositoryMetadata to QueryExecutionConverters in order to make it available to every class needing it. This also puts it closer to the data it is working on.

Original pull request: #249.

src/main/java/org/springframework/data/repository/core/support/AbstractRepositoryMetadata.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2015 the original author or authors.
+ * Copyright 2011-2017 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.
@@ -35,6 +35,7 @@ import org.springframework.util.Assert;
  * 
  * @author Oliver Gierke
  * @author Thomas Darimont
+ * @author Jens Schauder
  */
 public abstract class AbstractRepositoryMetadata implements RepositoryMetadata {
 
@@ -76,7 +77,7 @@ public abstract class AbstractRepositoryMetadata implements RepositoryMetadata {
 	 * @see org.springframework.data.repository.core.RepositoryMetadata#getReturnedDomainClass(java.lang.reflect.Method)
 	 */
 	public Class<?> getReturnedDomainClass(Method method) {
-		return unwrapWrapperTypes(typeInformation.getReturnType(method));
+		return QueryExecutionConverters.unwrapWrapperTypes(typeInformation.getReturnType(method)).getType();
 	}
 
 	/* 

src/main/java/org/springframework/data/repository/query/Parameter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2015 the original author or authors.
+ * Copyright 2008-2017 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.
@@ -34,6 +34,7 @@ import org.springframework.util.Assert;
  * Class to abstract a single parameter of a query method. It is held in the context of a {@link Parameters} instance.
  * 
  * @author Oliver Gierke
+ * @author Jens Schauder
  */
 public class Parameter {
 
@@ -201,7 +202,8 @@ public class Parameter {
 
 		TypeInformation<?> bound = parameterTypes.getTypeArguments().get(0);
 		TypeInformation<Object> returnType = ClassTypeInformation.fromReturnTypeOf(method);
-		return bound.equals(returnType.getActualType());
+
+		return bound.equals(QueryExecutionConverters.unwrapWrapperTypes(returnType));
 	}
 
 	/**

src/main/java/org/springframework/data/repository/util/QueryExecutionConverters.java

@@ -32,6 +32,7 @@ import java.util.Set;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.Future;
 import java.util.function.Supplier;
+import java.util.stream.Stream;
 
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.TypeDescriptor;
@@ -40,6 +41,7 @@ import org.springframework.core.convert.converter.GenericConverter;
 import org.springframework.core.convert.support.ConfigurableConversionService;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Slice;
+import org.springframework.data.util.TypeInformation;
 import org.springframework.scheduling.annotation.AsyncResult;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
@@ -68,6 +70,7 @@ import com.google.common.base.Optional;
  * @author Mark Paluch
  * @author Maciek Opała
  * @author Jacek Jackowiak
+ * @author Jens Schauder
  * @since 1.8
  */
 public abstract class QueryExecutionConverters {
@@ -239,6 +242,23 @@ public abstract class QueryExecutionConverters {
 		return source;
 	}
 
+	/**
+	 * Recursively unwraps well known wrapper types from the given {@link TypeInformation}.
+	 *
+	 * @param type must not be {@literal null}.
+	 */
+	public static TypeInformation<?> unwrapWrapperTypes(TypeInformation<?> type) {
+
+		Assert.notNull(type, "type must not be null");
+
+		Class<?> rawType = type.getType();
+
+		boolean needToUnwrap = Iterable.class.isAssignableFrom(rawType) || rawType.isArray() || supports(rawType)
+				|| Stream.class.isAssignableFrom(rawType);
+
+		return needToUnwrap ? unwrapWrapperTypes(type.getComponentType()) : type;
+	}
+
 	/**
 	 * Base class for converters that create instances of wrapper types such as Google Guava's and JDK 8's
 	 * {@code Optional} types.

src/test/java/org/springframework/data/repository/query/ParameterUnitTests.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2017 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.repository.query;
+
+import static org.hamcrest.MatcherAssert.*;
+import static org.hamcrest.Matchers.*;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Stream;
+
+import org.junit.Test;
+import org.springframework.core.MethodParameter;
+
+/**
+ * Unit tests for {@link Parameter}.
+ *
+ * @author Jens Schauder
+ */
+public class ParameterUnitTests {
+
+	@Test // DATAJPA-1185
+	public void classParameterWithSameTypeParameterAsReturnedListIsDynamicProjectionParameter() throws Exception {
+
+		Parameter parameter = new Parameter(getMethodParameter("dynamicProjectionWithList"));
+
+		assertThat(parameter.isDynamicProjectionParameter(), is(true));
+	}
+
+	@Test // DATAJPA-1185
+	public void classParameterWithSameTypeParameterAsReturnedStreamIsDynamicProjectionParameter() throws Exception {
+
+		Parameter parameter = new Parameter(getMethodParameter("dynamicProjectionWithStream"));
+
+		assertThat(parameter.isDynamicProjectionParameter(), is(true));
+	}
+
+	private MethodParameter getMethodParameter(String methodName) throws NoSuchMethodException {
+
+		return new MethodParameter( //
+				this.getClass().getDeclaredMethod( //
+						methodName, //
+						Class.class //
+				), //
+				0);
+	}
+
+	<T> List<T> dynamicProjectionWithList(Class<T> type) {
+		return Collections.emptyList();
+	}
+
+	<T> Stream<T> dynamicProjectionWithStream(Class<T> type) {
+		return null;
+	}
+}