DATACMNS-1261 - Apply Java 8 Functional types and Lambdas to simplify…

src/main/java/org/springframework/data/config/ConfigurationUtils.java

@@ -37,15 +37,13 @@ public interface ConfigurationUtils {
 	 * @return
 	 * @throws IllegalArgumentException if no {@link ResourceLoader} can be obtained from the {@link XmlReaderContext}.
 	 */
-	public static ResourceLoader getRequiredResourceLoader(XmlReaderContext context) {
+	static ResourceLoader getRequiredResourceLoader(XmlReaderContext context) {
 
 		Assert.notNull(context, "XmlReaderContext must not be null!");
 
 		ResourceLoader resourceLoader = context.getResourceLoader();
 
-		if (resourceLoader == null) {
-			throw new IllegalArgumentException("Could not obtain ResourceLoader from XmlReaderContext!");
-		}
+		Assert.notNull(resourceLoader, "Could not obtain ResourceLoader from XmlReaderContext!");
 
 		return resourceLoader;
 	}
@@ -57,7 +55,7 @@ public static ResourceLoader getRequiredResourceLoader(XmlReaderContext context)
 	 * @return
 	 * @throws IllegalArgumentException if no {@link ClassLoader} can be obtained from the given {@link XmlReaderContext}.
 	 */
-	public static ClassLoader getRequiredClassLoader(XmlReaderContext context) {
+	static ClassLoader getRequiredClassLoader(XmlReaderContext context) {
 		return getRequiredClassLoader(getRequiredResourceLoader(context));
 	}
 
@@ -68,15 +66,13 @@ public static ClassLoader getRequiredClassLoader(XmlReaderContext context) {
 	 * @return
 	 * @throws IllegalArgumentException if the given {@link ResourceLoader} does not expose a {@link ClassLoader}.
 	 */
-	public static ClassLoader getRequiredClassLoader(ResourceLoader resourceLoader) {
+	static ClassLoader getRequiredClassLoader(ResourceLoader resourceLoader) {
 
 		Assert.notNull(resourceLoader, "ResourceLoader must not be null!");
 
 		ClassLoader classLoader = resourceLoader.getClassLoader();
 
-		if (classLoader == null) {
-			throw new IllegalArgumentException("Could not obtain ClassLoader from ResourceLoader!");
-		}
+		Assert.notNull(classLoader, "Could not obtain ClassLoader from ResourceLoader!");
 
 		return classLoader;
 	}
@@ -88,16 +84,14 @@ public static ClassLoader getRequiredClassLoader(ResourceLoader resourceLoader)
 	 * @return
 	 * @throws IllegalArgumentException if the given {@link BeanDefinition} does not contain a bean class name.
 	 */
-	public static String getRequiredBeanClassName(BeanDefinition beanDefinition) {
+	static String getRequiredBeanClassName(BeanDefinition beanDefinition) {
 
 		Assert.notNull(beanDefinition, "BeanDefinition must not be null!");
 
 		String result = beanDefinition.getBeanClassName();
 
-		if (result == null) {
-			throw new IllegalArgumentException(
-					String.format("Could not obtain required bean class name from BeanDefinition!", beanDefinition));
-		}
+		Assert.notNull(result, String.format("Could not obtain required bean class name from BeanDefinition [%s]!",
+				beanDefinition));
 
 		return result;
 	}

src/main/java/org/springframework/data/repository/config/AnnotationRepositoryConfigurationSource.java

@@ -93,9 +93,8 @@ public AnnotationRepositoryConfigurationSource(AnnotationMetadata metadata, Clas
 
 		Map<String, Object> annotationAttributes = metadata.getAnnotationAttributes(annotation.getName());
 
-		if (annotationAttributes == null) {
-			throw new IllegalStateException(String.format("Unable to obtain annotation attributes for %s!", annotation));
-		}
+		Assert.state(annotationAttributes != null,
+				String.format("Unable to obtain annotation attributes for %s!", annotation));
 
 		this.attributes = new AnnotationAttributes(annotationAttributes);
 		this.enableAnnotationMetadata = new StandardAnnotationMetadata(annotation);

src/main/java/org/springframework/data/repository/config/RepositoryBeanDefinitionRegistrarSupport.java

@@ -76,13 +76,13 @@ public void registerBeanDefinitions(AnnotationMetadata annotationMetadata, BeanD
 		AnnotationRepositoryConfigurationSource configurationSource = new AnnotationRepositoryConfigurationSource(
 				annotationMetadata, getAnnotation(), resourceLoader, environment, registry);
 
-		RepositoryConfigurationExtension extension = getExtension();
-		RepositoryConfigurationUtils.exposeRegistration(extension, registry, configurationSource);
+		RepositoryConfigurationExtension configurationExtension = getExtension();
+		RepositoryConfigurationUtils.exposeRegistration(configurationExtension, registry, configurationSource);
 
-		RepositoryConfigurationDelegate delegate = new RepositoryConfigurationDelegate(configurationSource, resourceLoader,
-				environment);
+		RepositoryConfigurationDelegate delegate =
+				new RepositoryConfigurationDelegate(configurationSource, resourceLoader, environment);
 
-		delegate.registerRepositoriesIn(registry, extension);
+		delegate.registerRepositoriesIn(registry, configurationExtension);
 	}
 
 	/**

src/main/java/org/springframework/data/repository/config/RepositoryComponentProvider.java

@@ -36,6 +36,7 @@
 import org.springframework.data.repository.Repository;
 import org.springframework.data.repository.RepositoryDefinition;
 import org.springframework.data.repository.util.ClassUtils;
+import org.springframework.data.util.IterableUtils;
 import org.springframework.util.Assert;
 
 /**
@@ -61,15 +62,12 @@ public RepositoryComponentProvider(Iterable<? extends TypeFilter> includeFilters
 
 		super(false);
 
-		Assert.notNull(includeFilters, "Include filters must not be null!");
 		Assert.notNull(registry, "BeanDefinitionRegistry must not be null!");
 
 		this.registry = registry;
 
-		if (includeFilters.iterator().hasNext()) {
-			for (TypeFilter filter : includeFilters) {
-				addIncludeFilter(filter);
-			}
+		if (IterableUtils.isNotEmpty(includeFilters)) {
+			includeFilters.forEach(this::addIncludeFilter);
 		} else {
 			super.addIncludeFilter(new InterfaceTypeFilter(Repository.class));
 			super.addIncludeFilter(new AnnotationTypeFilter(RepositoryDefinition.class, true, true));
@@ -79,9 +77,11 @@ public RepositoryComponentProvider(Iterable<? extends TypeFilter> includeFilters
 	}
 
 	/**
-	 * Custom extension of {@link #addIncludeFilter(TypeFilter)} to extend the added {@link TypeFilter}. For the
-	 * {@link TypeFilter} handed we'll have two filters registered: one additionally enforcing the
-	 * {@link RepositoryDefinition} annotation, the other one forcing the extension of {@link Repository}.
+	 * Custom extension of {@link ClassPathScanningCandidateComponentProvider#addIncludeFilter(TypeFilter)}
+	 * to extend the added {@link TypeFilter}.
+	 *
+	 * For the {@link TypeFilter} handed we will have two filters registered: one additionally enforcing the
+	 * {@link RepositoryDefinition} annotation and the other forcing the extension of {@link Repository}.
 	 *
 	 * @see ClassPathScanningCandidateComponentProvider#addIncludeFilter(TypeFilter)
 	 */
@@ -123,11 +123,8 @@ public Set<BeanDefinition> findCandidateComponents(String basePackage) {
 
 		Set<BeanDefinition> candidates = super.findCandidateComponents(basePackage);
 
-		for (BeanDefinition candidate : candidates) {
-			if (candidate instanceof AnnotatedBeanDefinition) {
-				AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
-			}
-		}
+		candidates.stream().filter(bd -> bd instanceof AnnotatedBeanDefinition).forEach(bd ->
+				AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) bd));
 
 		return candidates;
 	}
@@ -153,7 +150,8 @@ public boolean isConsiderNestedRepositoryInterfaces() {
 	 * Controls whether nested inner-class {@link Repository} interface definitions should be considered for automatic
 	 * discovery. This defaults to {@literal false}.
 	 *
-	 * @param considerNestedRepositoryInterfaces
+	 * @param considerNestedRepositoryInterfaces boolean value indicating whether nested inner-class {@link Repository}
+	 * interface definitions should be considered for automatic discovery.
 	 */
 	public void setConsiderNestedRepositoryInterfaces(boolean considerNestedRepositoryInterfaces) {
 		this.considerNestedRepositoryInterfaces = considerNestedRepositoryInterfaces;
@@ -170,9 +168,9 @@ private static class InterfaceTypeFilter extends AssignableTypeFilter {
 		/**
 		 * Creates a new {@link InterfaceTypeFilter}.
 		 *
-		 * @param targetType
+		 * @param targetType {@link Class type} of the interface.
 		 */
-		public InterfaceTypeFilter(Class<?> targetType) {
+		private InterfaceTypeFilter(Class<?> targetType) {
 			super(targetType);
 		}
 
@@ -202,7 +200,7 @@ private static class AllTypeFilter implements TypeFilter {
 		 *
 		 * @param delegates must not be {@literal null}.
 		 */
-		public AllTypeFilter(List<TypeFilter> delegates) {
+		private AllTypeFilter(List<TypeFilter> delegates) {
 
 			Assert.notNull(delegates, "TypeFilter deleages must not be null!");
 			this.delegates = delegates;

src/main/java/org/springframework/data/repository/config/RepositoryConfigurationDelegate.java

@@ -31,6 +31,7 @@
 import org.springframework.core.env.StandardEnvironment;
 import org.springframework.core.io.ResourceLoader;
 import org.springframework.core.io.support.SpringFactoriesLoader;
+import org.springframework.data.repository.Repository;
 import org.springframework.data.repository.core.support.RepositoryFactorySupport;
 import org.springframework.util.Assert;
 
@@ -69,12 +70,13 @@ public class RepositoryConfigurationDelegate {
 	public RepositoryConfigurationDelegate(RepositoryConfigurationSource configurationSource,
 			ResourceLoader resourceLoader, Environment environment) {
 
-		this.isXml = configurationSource instanceof XmlRepositoryConfigurationSource;
+		Assert.notNull(resourceLoader, "ResourceLoader must not be null!");
+
 		boolean isAnnotation = configurationSource instanceof AnnotationRepositoryConfigurationSource;
+		this.isXml = configurationSource instanceof XmlRepositoryConfigurationSource;
 
-		Assert.isTrue(isXml || isAnnotation,
-				"Configuration source must either be an Xml- or an AnnotationBasedConfigurationSource!");
-		Assert.notNull(resourceLoader, "ResourceLoader must not be null!");
+		Assert.isTrue(this.isXml || isAnnotation,
+				"Configuration source must either be an XML-based or an Annotation-based RepositoryConfigurationSource!");
 
 		this.configurationSource = configurationSource;
 		this.resourceLoader = resourceLoader;
@@ -83,12 +85,14 @@ public RepositoryConfigurationDelegate(RepositoryConfigurationSource configurati
 	}
 
 	/**
-	 * Defaults the environment in case the given one is null. Used as fallback, in case the legacy constructor was
-	 * invoked.
+	 * Defaults the {@link Environment} in case the given one is {@literal null}.
+	 *
+	 * Used as fallback in case the legacy constructor was invoked.
 	 *
 	 * @param environment can be {@literal null}.
 	 * @param resourceLoader can be {@literal null}.
-	 * @return
+	 * @return the given {@link Environment} if not {@literal null} or an {@link Environment} obtained
+	 * from the {@link ResourceLoader} if {@link ResourceLoader} is {@link EnvironmentCapable}.
 	 */
 	private static Environment defaultEnvironment(@Nullable Environment environment,
 			@Nullable ResourceLoader resourceLoader) {
@@ -104,21 +108,22 @@ private static Environment defaultEnvironment(@Nullable Environment environment,
 	/**
 	 * Registers the found repositories in the given {@link BeanDefinitionRegistry}.
 	 *
-	 * @param registry
-	 * @param extension
-	 * @return {@link BeanComponentDefinition}s for all repository bean definitions found.
+	 * @param registry {@link BeanDefinitionRegistry} used to register {@link Repository Repositories}.
+	 * @param extension {@link RepositoryConfigurationExtension} containing store specific configuration meta-data.
+	 * @return {@link BeanComponentDefinition}s for all {@link Repository} bean definitions found.
 	 */
 	public List<BeanComponentDefinition> registerRepositoriesIn(BeanDefinitionRegistry registry,
 			RepositoryConfigurationExtension extension) {
 
 		extension.registerBeansForRoot(registry, configurationSource);
 
-		RepositoryBeanDefinitionBuilder builder = new RepositoryBeanDefinitionBuilder(registry, extension, resourceLoader,
-				environment);
+		RepositoryBeanDefinitionBuilder builder =
+				new RepositoryBeanDefinitionBuilder(registry, extension, resourceLoader, environment);
+
 		List<BeanComponentDefinition> definitions = new ArrayList<>();
 
-		for (RepositoryConfiguration<? extends RepositoryConfigurationSource> configuration : extension
-				.getRepositoryConfigurations(configurationSource, resourceLoader, inMultiStoreMode)) {
+		for (RepositoryConfiguration<? extends RepositoryConfigurationSource> configuration
+				: extension.getRepositoryConfigurations(configurationSource, resourceLoader, inMultiStoreMode)) {
 
 			BeanDefinitionBuilder definitionBuilder = builder.build(configuration);
 
@@ -152,7 +157,7 @@ public List<BeanComponentDefinition> registerRepositoriesIn(BeanDefinitionRegist
 	 * than a single type is considered a multi-store configuration scenario which will trigger stricter repository
 	 * scanning.
 	 *
-	 * @return
+	 * @return a boolean value indicating if multiple Spring Data store implementations are present on the classpath.
 	 */
 	private boolean multipleStoresDetected() {
 

src/main/java/org/springframework/data/repository/config/RepositoryConfigurationSourceSupport.java

@@ -72,7 +72,7 @@ public Streamable<BeanDefinition> getCandidates(ResourceLoader loader) {
 		scanner.setEnvironment(environment);
 		scanner.setResourceLoader(loader);
 
-		getExcludeFilters().forEach(it -> scanner.addExcludeFilter(it));
+		getExcludeFilters().forEach(scanner::addExcludeFilter);
 
 		return Streamable.of(() -> getBasePackages().stream()//
 				.flatMap(it -> scanner.findCandidateComponents(it).stream()));

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

@@ -15,8 +15,6 @@
  */
 package org.springframework.data.repository.query;
 
-import static java.lang.String.*;
-
 import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -41,11 +39,13 @@ public abstract class Parameters<S extends Parameters<S, T>, T extends Parameter
 
 	public static final List<Class<?>> TYPES = Arrays.asList(Pageable.class, Sort.class);
 
-	private static final String PARAM_ON_SPECIAL = format("You must not user @%s on a parameter typed %s or %s",
-			Param.class.getSimpleName(), Pageable.class.getSimpleName(), Sort.class.getSimpleName());
-	private static final String ALL_OR_NOTHING = String.format(
-			"Either use @%s on all parameters except %s and %s typed once, or none at all!", Param.class.getSimpleName(),
-			Pageable.class.getSimpleName(), Sort.class.getSimpleName());
+	private static final String PARAM_ON_SPECIAL =
+			String.format("You must not use @%s on a parameter typed %s or %s",
+					Param.class.getSimpleName(), Pageable.class.getSimpleName(), Sort.class.getSimpleName());
+
+	private static final String ALL_OR_NOTHING =
+			String.format("Either use @%s on all parameters except parameters of type %s and %s, or none at all!",
+					Param.class.getSimpleName(), Pageable.class.getSimpleName(), Sort.class.getSimpleName());
 
 	private final ParameterNameDiscoverer discoverer = new DefaultParameterNameDiscoverer();
 	private final int pageableIndex;

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

@@ -69,10 +69,11 @@ public QueryMethod(Method method, RepositoryMetadata metadata, ProjectionFactory
 
 		Parameters.TYPES.stream()//
 				.filter(type -> getNumberOfOccurences(method, type) > 1)//
-				.findFirst().ifPresent(type -> {
+				.findFirst()
+				.ifPresent(type -> {
 					throw new IllegalStateException(
-							String.format("Method must only one argument of type %s! Offending method: %s", type.getSimpleName(),
-									method.toString()));
+							String.format("Method must only have one argument of type %s! Offending method: %s",
+									type.getSimpleName(), method.toString()));
 				});
 
 		this.method = method;

src/main/java/org/springframework/data/util/IterableUtils.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright 2012-2018 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.util;
+
+import java.util.Collections;
+
+import org.springframework.lang.NonNull;
+import org.springframework.lang.Nullable;
+
+/**
+ * Utility class for working with {@link Iterable} objects.
+ *
+ * @author John Blum
+ * @see java.lang.Iterable
+ * @since 2.1.0
+ */
+public abstract class IterableUtils {
+
+	/**
+	 * Determines whether the given {@link Iterable} is empty.
+	 *
+	 * @param iterable {@link Iterable} to evaluate; can be {@literal null}.
+	 * @return {@literal true} if the given {@link Iterable} is empty,
+	 * otherwise return {@literal false}.
+	 * @see #nullSafeIterable(Iterable)
+	 * @see java.lang.Iterable
+	 */
+	public static boolean isEmpty(@Nullable Iterable<?> iterable) {
+		return !isNotEmpty(iterable);
+	}
+
+	/**
+	 * Determines if the given {@link Iterable} is not empty.
+	 *
+	 * @param iterable {@link Iterable} to evaluate; can be {@literal null}.
+	 * @return {@literal true} if the given {@link Iterable} is not empty,
+	 * otherwise return {@literal false}.
+	 * @see #nullSafeIterable(Iterable)
+	 * @see java.lang.Iterable
+	 */
+	public static boolean isNotEmpty(@Nullable Iterable<?> iterable) {
+		return nullSafeIterable(iterable).iterator().hasNext();
+	}
+
+	/**
+	 * Protects against {@literal null} {@link Iterable} references.
+	 *
+	 * @param <T> {@link Class type} of elements contained by the {@link Iterable}.
+	 * @param it {@link Iterable} to safe-guard from {@literal null}.
+	 * @return the given {@link Iterable} if not {@literal null} or an empty {@link Iterable}.
+	 * @see java.lang.Iterable
+	 */
+	@NonNull
+	public static <T> Iterable<T> nullSafeIterable(@Nullable Iterable<T> it) {
+		return it != null ? it : Collections::emptyIterator;
+	}
+}