DATAJPA-332 - Optimization for SimpleJpaRepository.findAll(…) taking Iterable.

We now shortcut the execution of SimpleJpaRepository.findAll(Iterable<Integer> ids) to return an empty collection in case no ids or null are given. Previously building a query with an IN clause failed with an empty parameter list given.

src/main/java/org/springframework/data/jpa/repository/support/SimpleJpaRepository.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2012 the original author or authors.
+ * Copyright 2008-2013 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.
@@ -253,6 +253,10 @@ public class SimpleJpaRepository<T, ID extends Serializable> implements JpaRepos
 	 */
 	public List<T> findAll(Iterable<ID> ids) {
 
+		if (ids == null || !ids.iterator().hasNext()) {
+			return Collections.emptyList();
+		}
+
 		return getQuery(new Specification<T>() {
 			public Predicate toPredicate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
 				Path<?> path = root.get(entityInformation.getIdAttribute());

src/test/java/org/springframework/data/jpa/repository/UserRepositoryTests.java

@@ -24,6 +24,7 @@ import static org.springframework.data.jpa.domain.sample.UserSpecifications.*;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
@@ -1049,6 +1050,16 @@ public class UserRepositoryTests {
 		assertThat(repository.countUsersByFirstname("Dave"), is(1));
 	}
 
+	/**
+	 * @see DATAJPA-332
+	 */
+	@Test
+	public void findAllReturnsEmptyIterableIfNoIdsGiven() {
+
+		assertThat(repository.findAll(Collections.<Integer> emptySet()), is(emptyIterable()));
+		assertThat(repository.findAll((Iterable<Integer>) null), is(emptyIterable()));
+	}
+
 	private Page<User> executeSpecWithSort(Sort sort) {
 
 		flushTestUsers();