DATAJPA-1301 - Improved null handling for TupleBackedMap.

TupleBackedMap now properly distinguishes between tuple elements with a null value and non-existing elements.

Original pull request: #262.

src/main/java/org/springframework/data/jpa/repository/query/AbstractJpaQuery.java

@@ -317,6 +317,7 @@ public Object convert(Object source) {
 		 */
 		private static class TupleBackedMap implements Map<String, Object> {
 
+			public static final String UNMODIFIABLE_MESSAGE = "A TupleBackedMap cannot be modified.";
 			private final Tuple tuple;
 
 			TupleBackedMap(Tuple tuple) {
@@ -333,39 +334,68 @@ public boolean isEmpty() {
 				return tuple.getElements().isEmpty();
 			}
 
+			/**
+			 * If the key is not a {@code String} or not a key of the backing {@link Tuple} this returns {@code false}.
+			 * Otherwise this returns {@code true} even when the value from the backing {@code Tuple} is {@code null}.
+			 *
+			 * @param key the key for which to get the value from the map.
+			 * @return wether the key is an element of the backing tuple.
+			 */
 			@Override
 			public boolean containsKey(Object key) {
-				return key instanceof String && tuple.get((String) key) != null;
+
+				try {
+					tuple.get((String) key);
+					return true;
+				} catch (IllegalArgumentException e) {
+					return false;
+				}
 			}
 
 			@Override
 			public boolean containsValue(Object value) {
 				return Arrays.asList(tuple.toArray()).contains(value);
 			}
 
+			/**
+			 * If the key is not a {@code String} or not a key of the backing {@link Tuple} this returns {@code null}.
+			 * Otherwise the value from the backing {@code Tuple} is returned, which also might be {@code null}.
+			 *
+			 * @param key the key for which to get the value from the map.
+			 * @return the value of the backing {@link Tuple} for that key or {@code null}.
+			 */
 			@Override
 			public Object get(Object key) {
-				return key instanceof String ? tuple.get((String) key) : null;
+
+				if (!(key instanceof String)) {
+					return null;
+				}
+
+				try {
+					return tuple.get((String) key);
+				} catch (IllegalArgumentException e) {
+					return null;
+				}
 			}
 
 			@Override
 			public Object put(String key, Object value) {
-				throw new UnsupportedOperationException("A TupleBackedMap cannot be modified");
+				throw new UnsupportedOperationException(UNMODIFIABLE_MESSAGE);
 			}
 
 			@Override
 			public Object remove(Object key) {
-				throw new UnsupportedOperationException("A TupleBackedMap cannot be modified");
+				throw new UnsupportedOperationException(UNMODIFIABLE_MESSAGE);
 			}
 
 			@Override
 			public void putAll(Map<? extends String, ?> m) {
-				throw new UnsupportedOperationException("A TupleBackedMap cannot be modified");
+				throw new UnsupportedOperationException(UNMODIFIABLE_MESSAGE);
 			}
 
 			@Override
 			public void clear() {
-				throw new UnsupportedOperationException("A TupleBackedMap cannot be modified");
+				throw new UnsupportedOperationException(UNMODIFIABLE_MESSAGE);
 			}
 
 			@Override

src/test/java/org/springframework/data/jpa/repository/EclipseLinkNamespaceUserRepositoryTests.java

@@ -99,6 +99,13 @@ public void queryProvidesCorrectNumberOfParametersForNativeQuery() {
 	@Override
 	public void supportsProjectionsWithNativeQueriesAndCamelCaseProperty() {}
 
+	/**
+	 * Ignored until https://bugs.eclipse.org/bugs/show_bug.cgi?id=525319 is fixed.
+	 */
+	@Override
+	@Test // DATAJPA-1301
+	public void returnsNullValueInMap() {}
+
 	/**
 	 * TODO: Remove, once https://bugs.eclipse.org/bugs/show_bug.cgi?id=289141 is fixed.
 	 */

src/test/java/org/springframework/data/jpa/repository/UserRepositoryTests.java

@@ -31,6 +31,7 @@
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.function.Consumer;
 import java.util.stream.Collectors;
@@ -2235,6 +2236,27 @@ public void bindsNativeQueryResultsToProjectionByName() {
 		assertThat(element.getLastname(), is("Arrasz"));
 	}
 
+	@Test // DATAJPA-1301
+	public void returnsNullValueInMap() {
+
+		Assume
+				.assumeTrue(getHibernateVersion().isGreaterThanOrEqualTo(HIBERNATE_VERSION_SUPPORTING_TUPLE_ON_NATIVE_QUERIES));
+
+		firstUser.setLastname(null);
+		flushTestUsers();
+
+		Map<String, Object> map = repository.findMapWithNullValues();
+
+		assertThat(map.keySet(), contains("firstname", "lastname"));
+		assertThat(map.containsKey("firstname"), is(true));
+		assertThat(map.containsKey("lastname"), is(true));
+
+		assertThat(map.get("firstname"), is((Object) "Oliver"));
+		assertThat(map.get("lastname"), is(nullValue()));
+		assertThat(map.get("non-existent"), is(nullValue()));
+		assertThat(map.get(new Object()), is(nullValue()));
+	}
+
 	private Page<User> executeSpecWithSort(Sort sort) {
 
 		flushTestUsers();

src/test/java/org/springframework/data/jpa/repository/sample/UserRepository.java

@@ -18,6 +18,7 @@
 import java.util.Collection;
 import java.util.Date;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.stream.Stream;
 
@@ -489,6 +490,10 @@ List<User> findUsersByFirstnameForSpELExpressionWithParameterIndexOnlyWithEntity
 	// DATAJPA-1273
 	List<NameOnly> findByNamedQueryWithAliasInInvertedOrder();
 
+	// DATAJPA-1301
+	@Query("select firstname as firstname, lastname as lastname from User u where u.firstname = 'Oliver'")
+	Map<String, Object> findMapWithNullValues();
+
 	interface RolesAndFirstname {
 
 		String getFirstname();