DATACMNS-836 - Introduced base class for reactive repository factories.

Introduced ReactiveRepositoryFactorySupport so that validation for the presence of all required converters (e.g. RxJava 1) does not have to be repeated in individual stores.

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

@@ -0,0 +1,99 @@
+/*
+ * Copyright 2016 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.core.support;
+
+import java.lang.reflect.Method;
+import java.util.Arrays;
+
+import org.reactivestreams.Publisher;
+import org.springframework.dao.InvalidDataAccessApiUsageException;
+import org.springframework.data.repository.core.RepositoryMetadata;
+import org.springframework.data.repository.util.ReactiveWrapperConverters;
+import org.springframework.data.repository.util.ReactiveWrappers;
+import org.springframework.util.ClassUtils;
+
+/**
+ * Base class for repository factories to use reactive support. Centralizes the validation of the classpath setup in
+ * case a repository uses reactive types.
+ * 
+ * @author Mark Paluch
+ * @author Oliver Gierke
+ * @since 2.0
+ */
+public abstract class ReactiveRepositoryFactorySupport extends RepositoryFactorySupport {
+
+	/* 
+	 * (non-Javadoc)
+	 * @see org.springframework.data.repository.core.support.RepositoryFactorySupport#validate(org.springframework.data.repository.core.RepositoryMetadata)
+	 */
+	@Override
+	protected void validate(RepositoryMetadata repositoryMetadata) {
+
+		if (!ReactiveWrappers.isAvailable()) {
+
+			throw new InvalidDataAccessApiUsageException(
+					String.format("Cannot implement repository %s without reactive library support.",
+							repositoryMetadata.getRepositoryInterface().getName()));
+		}
+
+		if (RxJavaOneConversionSetup.REACTIVE_STREAMS_PRESENT) {
+
+			Arrays.stream(repositoryMetadata.getRepositoryInterface().getMethods())
+					.forEach(RxJavaOneConversionSetup::validate);
+		}
+	}
+
+	/**
+	 * We need to make sure that the necessary conversion libraries are in place if the repository interface uses RxJava 1
+	 * types.
+	 *
+	 * @author Mark Paluch
+	 * @author Oliver Gierke
+	 */
+	private static class RxJavaOneConversionSetup {
+
+		private static final boolean REACTIVE_STREAMS_PRESENT = ClassUtils.isPresent("org.reactivestreams.Publisher",
+				RxJavaOneConversionSetup.class.getClassLoader());
+
+		/**
+		 * Reactive MongoDB support requires reactive wrapper support. If return type/parameters are reactive wrapper types,
+		 * then it's required to be able to convert these.
+		 *
+		 * @param method the method to validate.
+		 */
+		private static void validate(Method method) {
+
+			if (ReactiveWrappers.supports(method.getReturnType())
+					&& !ClassUtils.isAssignable(Publisher.class, method.getReturnType())
+					&& !ReactiveWrapperConverters.supports(method.getReturnType())) {
+
+				throw new InvalidDataAccessApiUsageException(
+						String.format("No reactive type converter found for type %s used in %s, method %s.",
+								method.getReturnType().getName(), method.getDeclaringClass().getName(), method));
+			}
+
+			Arrays.stream(method.getParameterTypes()) //
+					.filter(ReactiveWrappers::supports) //
+					.filter(parameterType -> !ClassUtils.isAssignable(Publisher.class, parameterType)) //
+					.filter(parameterType -> !ReactiveWrapperConverters.supports(parameterType)) //
+					.forEach(parameterType -> {
+						throw new InvalidDataAccessApiUsageException(
+								String.format("No reactive type converter found for type %s used in %s, method %s.",
+										parameterType.getName(), method.getDeclaringClass().getName(), method));
+					});
+		}
+	}
+}