DATACMNS-764 - Java 8 polishing.

Use Streamable in configuration APIs for more efficient, lazy traversal of source lists. Introduced SelectionSet.of(…) to move away from constructors. Avoid the use of null in SelectionSet.

Original pull request: #201.

src/test/java/org/springframework/data/repository/config/AnnotationRepositoryConfigurationSourceUnitTests.java

@@ -19,7 +19,6 @@ import static org.assertj.core.api.Assertions.*;
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
-import java.util.Collection;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -32,6 +31,7 @@ import org.springframework.core.io.DefaultResourceLoader;
 import org.springframework.core.io.ResourceLoader;
 import org.springframework.core.type.AnnotationMetadata;
 import org.springframework.core.type.StandardAnnotationMetadata;
+import org.springframework.data.util.Streamable;
 
 /**
  * Unit tests for {@link AnnotationRepositoryConfigurationSource}.
@@ -65,7 +65,7 @@ public class AnnotationRepositoryConfigurationSourceUnitTests {
 	@Test // DATACMNS-47
 	public void evaluatesExcludeFiltersCorrectly() {
 
-		Collection<BeanDefinition> candidates = source.getCandidates(new DefaultResourceLoader());
+		Streamable<BeanDefinition> candidates = source.getCandidates(new DefaultResourceLoader());
 		assertThat(candidates).hasSize(1);
 
 		BeanDefinition candidate = candidates.iterator().next();

src/test/java/org/springframework/data/repository/config/SelectionSetUnitTests.java

@@ -1,8 +1,25 @@
+/*
+ * 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.config;
 
 import static java.util.Arrays.*;
 import static java.util.Collections.*;
-import static org.junit.Assert.*;
+import static org.assertj.core.api.Assertions.*;
+
+import java.util.Optional;
 
 import org.junit.Test;
 
@@ -10,53 +27,53 @@ import org.junit.Test;
  * Unit tests for {@link SelectionSet}
  *
  * @author Jens Schauder
+ * @author Oliver Gierke
  */
 public class SelectionSetUnitTests {
 
 	@Test // DATACMNS-764
 	public void returnsUniqueResult() {
-		assertEquals("single value", new SelectionSet<>(singleton("single value")).uniqueResult());
+		assertThat(SelectionSet.of(singleton("single value")).uniqueResult()).hasValue("single value");
 	}
 
 	@Test // DATACMNS-764
 	public void emptyCollectionReturnsNull() {
-		assertNull(new SelectionSet<Object>(emptySet()).uniqueResult());
+		assertThat(SelectionSet.of(emptySet()).uniqueResult()).isEmpty();
 	}
 
 	@Test(expected = IllegalStateException.class) // DATACMNS-764
 	public void multipleElementsThrowException() {
-		new SelectionSet<>(asList("one", "two")).uniqueResult();
+		SelectionSet.of(asList("one", "two")).uniqueResult();
 	}
 
 	@Test(expected = NullPointerException.class) // DATACMNS-764
 	public void throwsCustomExceptionWhenConfigured() {
 
-		new SelectionSet<>(asList("one", "two"), c -> {
+		SelectionSet.of(asList("one", "two"), c -> {
 			throw new NullPointerException();
 		}).uniqueResult();
 	}
 
 	@Test // DATACMNS-764
 	public void usesFallbackWhenConfigured() {
-
-		String value = new SelectionSet<>(asList("one", "two"), c -> String.valueOf(c.size())).uniqueResult();
-
-		assertEquals("2", value);
+		assertThat(SelectionSet.of(asList("one", "two"), c -> Optional.of(String.valueOf(c.size()))).uniqueResult())
+				.hasValue("2");
 	}
 
 	@Test // DATACMNS-764
 	public void returnsUniqueResultAfterFilter() {
 
-		SelectionSet<String> selection = new SelectionSet<>(asList("one", "two", "three")).filterIfNecessary(s -> s.contains("w"));
+		SelectionSet<String> selection = SelectionSet.of(asList("one", "two", "three"))
+				.filterIfNecessary(s -> s.contains("w"));
 
-		assertEquals("two", selection.uniqueResult());
+		assertThat(selection.uniqueResult()).hasValue("two");
 	}
 
 	@Test // DATACMNS-764
 	public void ignoresFilterWhenResultIsAlreadyUnique() {
 
-		SelectionSet<String> selection = new SelectionSet<>(asList("one")).filterIfNecessary(s -> s.contains("w"));
+		SelectionSet<String> selection = SelectionSet.of(asList("one")).filterIfNecessary(s -> s.contains("w"));
 
-		assertEquals("one", selection.uniqueResult());
+		assertThat(selection.uniqueResult()).hasValue("one");
 	}
 }