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copied!<p>I also couldn't get <code>@Fetch(FetchMode.JOIN)</code> to work when using JPA <em>(although it works fine when using the hibernate Criteria api)</em> and I also couldn't find any examples explaining why, but I can think of a few workarounds.</p> <p>The most straightforward way to load the Groups eagerly, is to use JPQL:</p> <pre><code>public interface PersonRepository extends JpaRepository<Person, String>{ @Query(value = "select distinct p from Person p left join fetch p.groups") List<Person> getAllPersons(); } </code></pre> <p>As you are using spring-data-jpa, you could also load the Groups eagerly by using a <code>Specification</code>. (As of 1.4.x you can chain specs that return null).</p> <pre><code>final Specification<Person> fetchGroups = new Specification<Person>() { @Override public Predicate toPredicate(Root<Person> root, CriteriaQuery<?> query, CriteriaBuilder cb) { root.fetch("groups", JoinType.LEFT); query.distinct(true); return null; } }; </code></pre> <p>If neither of these is an option for you, your best bet is probably to use <code>@Fetch(FetchMode.SUBSELECT)</code>.</p> <p>Another option is to use <code>@Fetch(FetchMode.SELECT)</code> in combination with <code>@BatchSize</code>. <code>@BatchSize</code> helps to solve the problem of the n+1 queries. By tweaking the batch size you can reduce the amount of queries executed to CEIL(n/batch_size)+1.</p> <pre><code>@Entity @Table(name = "persons") public class Person { @Id String name; @ManyToMany(fetch = FetchType.EAGER) @BatchSize(size = 20) Set<Group> groups = new HashSet<>(); } @Entity @Table(name = "groups") public class Group { @Id String name; @ManyToMany(mappedBy = "groups", fetch = FetchType.LAZY) Set<Person> persons = new HashSet<>(); } public interface PersonRepository extends JpaRepository<Person, String>{} </code></pre> <p>This mapping results in the following sql when you run <code>personRepository.findAll();</code> on a database containing 10 persons and <code>@BatchSize</code> set to 5.</p> <pre><code>Hibernate: select person0_.name as name1_ from persons person0_ Hibernate: select groups0_.persons_name as persons1_1_1_, groups0_.groups_name as groups2_1_, group1_.name as name0_0_ from persons_groups groups0_ inner join groups group1_ on groups0_.groups_name=group1_.name where groups0_.persons_name in ( ?, ?, ?, ?, ? ) Hibernate: select groups0_.persons_name as persons1_1_1_, groups0_.groups_name as groups2_1_, group1_.name as name0_0_ from persons_groups groups0_ inner join groups group1_ on groups0_.groups_name=group1_.name where groups0_.persons_name in ( ?, ?, ?, ?, ? ) </code></pre> <p><em>Note that <code>@BatchSize</code> also works for collections mapped with <code>FetchType.LAZY</code>.</em></p>

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