如何使用spring数据存储库进行延迟获取？

Question

数据库表

发表
的代码
的 ref_post_tag
帖子和标记具有多对多关系

实体

发布

@Entity
@Table(name = "post")
public class Post implements Serializable{
    private static final long serialVersionUID = 1783734013146305964L;

    public enum Status {
        DRAFT, REMOVED, LIVE;
    }

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.AUTO)
    private String id;

    @Column(name = "title")
    private String title;

    @Column(name = "create_time")
    private LocalDateTime createTime;

    @Column(name = "update_time")
    private LocalDateTime updateTime;

    @Column(name = "content")
    private String content;

    @Column(name = "status")
    @Enumerated(EnumType.STRING)
    private Status status;

    @ManyToMany
    @JoinTable(
            name = "ref_post_tag",
            joinColumns = @JoinColumn(name="post_id",referencedColumnName = "id"), inverseJoinColumns = @JoinColumn(name="tag_id", referencedColumnName = "id"))
    private List<Tag> tagList;
...
}  

标签

@Entity
@Table(name="tag")
public class Tag implements Serializable{
    private static final long serialVersionUID = -7015657012681544984L;

    @Id
    @Column(name="id")
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;

    @Column(name="name")
    private String name;

    @Column(name="description")
    private String description;

    @ManyToMany(mappedBy = "tagList")
    private List<Post> postList;

    public Integer getId() {

        return id;
    }
...
}

Tag Repo

public interface TagRepo extends CrudRepository<Tag, Integer>{
}

服务实施

@Service
public class TagServiceImpl implements TagService{

    @Autowired
    private TagRepo tagRepo;

    @Override
    public void addTag(Tag tag) {
        tagRepo.save(tag);
    }

    @Override
    public Tag getTag(Integer id) {
        Tag tag = tagRepo.findOne(id);
        return tag;
    }

    @Override
    public List<Tag> findAllTags() {
        return CollectionUtil.toArrayList(tagRepo.findAll());
    }
}

样本测试（更新）

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = TestContextConfiguration.class)
@Transactional
public abstract class ServiceTest {
}

public class TagServiceTest extends ServiceTest{

    @Autowired
    private TagService tagService;

    @Autowired
    private TagRepo tagRepo;

    @Test
    @Transactional
    public void addTag() throws Exception {
        Tag tag = new Tag();
        tag.setName("new tag");
        tag.setDescription("this is a new tag");
        tagService.addTag(tag);

        Tag tagCreated = tagRepo.findOne(tag.getId());
        assertNotNull(tagCreated);
        assertEquals(tagCreated.getName(), tag.getName());

    }

    @Test
    public void getTag() throws Exception {
        Tag tag = tagService.getTag(1); // tag "java" has an ID of "1"
        assertNotNull(tag);
        assertEquals(tag.getName(), "java");
        assertEquals(143,tag.getPostList().size()); // 143 posts under tag "java"
    }

}

问题

样本测试用例通过。这意味着提取标记中的 postList 也会被急切地获取和填充。

默认情况下，Spring数据存储库的方法是急切地提取吗？ 如果是，将此更改为延迟提取的最佳方式是什么？