JPA manyToMany未持久存在于关联表中

Question

我正在尝试以下单元测试：

    @Test
    @Transactional
    public void thatFolderLocationAssociationTableIsWorking() {
        Location l1 = new DomesticLocation();
        l1.setDeptName("Test name 1");
        Location l2 = new DomesticLocation();
        l2.setDeptName("Test name 2");

        KMLFolder k1 = new KMLFolder();
        k1.setName("Test name 1");
        KMLFolder k2 = new KMLFolder();
        k1.setName("Test name 2");

        List<Location> locations = new ArrayList<Location>();
        locations.add(l1);
        locations.add(l2);
        k1.setLocations(locations);
        kmlFolderServiceImpl.save(k1);

        assertEquals("Test name 1", kmlFolderServiceImpl.find(1L).getLocations().get(0).getDeptName());
        assertEquals("Test name 2", kmlFolderServiceImpl.find(1L).getLocations().get(1).getDeptName());

                //The following line gets the NPE
        assertEquals("Test name 1", locationServiceImpl.find(1L).getKmlFolderList().get(0).getName());
    }

我正在尝试从Locations检索KMLFolder.getName()的laster断言上获得NPE。其他断言正在工作，在这里我从KMLFolder获得Location名称。

这是我的JPA定义：

@ManyToMany(mappedBy="kmlFolderList", cascade=CascadeType.ALL)
private List<Location> locations = new ArrayList<Location>();

@ManyToMany
@JoinTable(name="LOCATION_KMLFOLDER",
    joinColumns={@JoinColumn(name="KMLFOLDER_ID", referencedColumnName="ID")},
    inverseJoinColumns={@JoinColumn(name="LOCATION_ID", referencedColumnName="ID")}
)

运行测试时，正在创建适当的表。 这是控制台输出：

Hibernate: 
    create table project.LOCATION_KMLFOLDER (
        KMLFOLDER_ID bigint not null,
        LOCATION_ID bigint not null
    ) ENGINE=InnoDB 
...
Hibernate: 
    alter table project.LOCATION_KMLFOLDER 
        add index FK_lqllrwb2t5cn0cbxxx3ms26ku (LOCATION_ID), 
        add constraint FK_lqllrwb2t5cn0cbxxx3ms26ku 
        foreign key (LOCATION_ID) 
        references project.KMLFolder (id)
Hibernate: 
    alter table .LOCATION_KMLFOLDER 
        add index FK_ckj00nos13yojmcyvtefgk9pl (KMLFOLDER_ID), 
        add constraint FK_ckj00nos13yojmcyvtefgk9pl 
        foreign key (KMLFOLDER_ID) 
        references project.Locations (id)

控制台未按预期显示在LOCATION_KNLFOLDER表中的插入内容。 为什么会这样呢？

Answer 1

您正在初始化Hibernate忽略的关联的相反方面，而不是（或除了）初始化关联的所有者方面之外，Hibernate不会忽略。

所有者方是没有mappedBy属性的方。