DATACMNS-1556 - General performance improvements in repository execution.

We now avoid the allocation of an Optional instance in the lookup of a dynamic projection in ParameterAccessor. Also, Lazy now exposes a ….getNullable() to be favored over ….getOptional() for hot code paths.

Replaced Stream and Optional usage with for-loops and nullable return values. Reuse parameter names to avoid repeated annotation lookups. Reuse result from Parameters.getBindable(). Introduce ParametersParameterAccessor.getValues() to consistently reuse a single accessor instance allowing access to the unwrapped values. Introduce type cache to QueryExecutionConverters to quickly reject types that do not require wrapping. Avoid recalculation of QueryMethod.isCollectionQuery().

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

@@ -146,7 +146,7 @@ public class ResultProcessorUnitTests {
 		ResultProcessor factory = getProcessor("findOneDynamic", Class.class);
 		assertThat(factory.withDynamicProjection(accessor)).isEqualTo(factory);
 
-		doReturn(Optional.of(SampleProjection.class)).when(accessor).getDynamicProjection();
+		doReturn(SampleProjection.class).when(accessor).findDynamicProjection();
 
 		ResultProcessor processor = factory.withDynamicProjection(accessor);
 		assertThat(processor.getReturnedType().getReturnedType()).isEqualTo(SampleProjection.class);

src/test/java/org/springframework/data/util/LazyUnitTests.java

@@ -28,8 +28,9 @@ import org.mockito.junit.MockitoJUnitRunner;
 
 /**
  * Unit tests for {@link Lazy}.
- * 
+ *
  * @author Oliver Gierke
+ * @author Mark Paluch
  */
 @RunWith(MockitoJUnitRunner.class)
 public class LazyUnitTests {
@@ -86,6 +87,11 @@ public class LazyUnitTests {
 		assertThat(Lazy.of(() -> null).getOptional()).isEmpty();
 	}
 
+	@Test // DATACMNS-1556
+	public void allowsNullableValue() {
+		assertThat(Lazy.of(() -> null).getNullable()).isNull();
+	}
+
 	@Test
 	public void ignoresElseIfValuePresent() {