DATACMNS-1081 - Add ReactiveQuerydslPredicateExecutor.

We now ship with a common interface for reactive repositories that want to support Querydsl.

Original Pull Request: #331

src/main/java/org/springframework/data/querydsl/ReactiveQuerydslPredicateExecutor.java

@@ -0,0 +1,97 @@
+/*
+ * Copyright 2019 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.querydsl;
+
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+import org.springframework.data.domain.Sort;
+
+import com.querydsl.core.types.OrderSpecifier;
+import com.querydsl.core.types.Predicate;
+
+/**
+ * Interface to issue queries using Querydsl {@link Predicate} instances.
+ *
+ * @author Mark Paluch
+ * @since 2.2
+ */
+public interface ReactiveQuerydslPredicateExecutor<T> {
+
+	/**
+	 * Returns a single entity matching the given {@link Predicate} or {@link Mono#empty()} if none was found.
+	 *
+	 * @param predicate must not be {@literal null}.
+	 * @return a single entity matching the given {@link Predicate} or {@link Mono#empty()} if none was found.
+	 * @throws org.springframework.dao.IncorrectResultSizeDataAccessException if the predicate yields more than one
+	 *           result.
+	 */
+	Mono<T> findOne(Predicate predicate);
+
+	/**
+	 * Returns all entities matching the given {@link Predicate}. In case no match could be found, {@link Flux} emits no
+	 * items.
+	 *
+	 * @param predicate must not be {@literal null}.
+	 * @return all entities matching the given {@link Predicate}.
+	 */
+	Flux<T> findAll(Predicate predicate);
+
+	/**
+	 * Returns all entities matching the given {@link Predicate} applying the given {@link Sort}. In case no match could
+	 * be found, {@link Flux} emits no items.
+	 *
+	 * @param predicate must not be {@literal null}.
+	 * @param sort the {@link Sort} specification to sort the results by, may be {@link Sort#empty()}, must not be
+	 *          {@literal null}.
+	 * @return all entities matching the given {@link Predicate}.
+	 */
+	Flux<T> findAll(Predicate predicate, Sort sort);
+
+	/**
+	 * Returns all entities matching the given {@link Predicate} applying the given {@link OrderSpecifier}s. In case no
+	 * match could be found, {@link Flux} emits no items.
+	 *
+	 * @param predicate must not be {@literal null}.
+	 * @param orders the {@link OrderSpecifier}s to sort the results by.
+	 * @return all entities matching the given {@link Predicate} applying the given {@link OrderSpecifier}s.
+	 */
+	Flux<T> findAll(Predicate predicate, OrderSpecifier<?>... orders);
+
+	/**
+	 * Returns all entities ordered by the given {@link OrderSpecifier}s.
+	 *
+	 * @param orders the {@link OrderSpecifier}s to sort the results by.
+	 * @return all entities ordered by the given {@link OrderSpecifier}s.
+	 */
+	Flux<T> findAll(OrderSpecifier<?>... orders);
+
+	/**
+	 * Returns the number of instances matching the given {@link Predicate}.
+	 *
+	 * @param predicate the {@link Predicate} to count instances for, must not be {@literal null}.
+	 * @return the number of instances matching the {@link Predicate}.
+	 */
+	Mono<Long> count(Predicate predicate);
+
+	/**
+	 * Checks whether the data store contains elements that match the given {@link Predicate}.
+	 *
+	 * @param predicate the {@link Predicate} to use for the existence check, must not be {@literal null}.
+	 * @return {@literal true} if the data store contains elements that match the given {@link Predicate}.
+	 */
+	Mono<Boolean> exists(Predicate predicate);
+}