SequenceGenerator在JUnit测试中不起作用？

Question

I try to test the persistence of some entities with an in-memory H2 DB but I recognized that @SequenceGenerator will never be invoked as it should be, neither when running by build platform, nor when running it with RunAs->JUnit test in Eclipse.

What I can say for sure is that the sequences are generated inside the H2 DB. I can even select them when I connect to this generated H2. So it's definitely not a problem inside H2 but with Hibernate. (Usually Hibernate automatically assigns an ID when persisting an Entity which needs one).

The entity

@Entity
@Table(name = "HOUSE_USERDATA")
public class UserData {

@Id
@Column(name = "HU_ID")
@GeneratedValue(generator = "SEQ_HOUSE_USERDATA", strategy = GenerationType.SEQUENCE)
@SequenceGenerator(sequenceName = "SEQ_HOUSE_USERDATA", name = "SEQ_HOUSE_USERDATA", allocationSize = 2)
private Long huId;

@Column(name = "HU_DATA")
@Size(max = 1000)
private String m_data;

@ManyToOne
@JoinColumn(name = "HR_ID")
private Registry m_registry;

//more code [...]
}

The reference in the referencing Entity...

  @OneToMany(mappedBy = "registry")
  private List<UserData> userDataList;

The persistence unit...

<persistence-unit name="test" transaction-type="RESOURCE_LOCAL">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>
    <class>com.foo.bar.all.entity</class>
    <!-- all entity references -->
    <exclude-unlisted-classes>false</exclude-unlisted-classes>
    <properties>
        <property name="hibernate.archive.autodetection" value="class"/>
        <property name="hibernate.connection.username" value="sa"/>
        <property name="hibernate.connection.password" value=""/>
        <property name="hibernate.connection.driver_class" value="org.h2.Driver"/>
        <property name="hibernate.connection.url" 
        value="jdbc:h2:inmemory;INIT=runscript from 'classpath:testscripts/drop_h2.sql'\;runscript from 'classpath:testscripts/create.sql'"/>
        <property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect" />
        <property name="hibernate.hbm2ddl.auto" value="create-drop"/>
        <property name="hibernate.show_sql" value="true" />
        <property name="hibernate.format_sql" value="true" />
        <property name="hibernate.use_sql_comments" value="true" />
    </properties>
</persistence-unit>

The invocation in JUnit test...

Registry registry = new Registry();
registry.setClientId("clientId");
List<UserData> userDataList = new ArrayList<>();
UserData userData1 = new UserData();
userData1.setData("User defined data 1.");
userData1.setRegistry(registry);
UserData userData2 = new UserData();
userData2.setData("User defined data 2.");
userData2.setRegistry(registry);
userDataList.add(userData1);
userDataList.add(userData2);
registry.setUserDataList(userDataList);


entityManager.persist(registry);


Registry result = entityManager.find(Registry.class, "clientId");
//MUST NOT BE NULL, BUT IS NULL
assertThat(result.getUserDataList().get(0).getId(), is(not(nullValue())))

Other values are persisted properly. Only the IDs were not generated. (I wonder why this test works at all for all the other values since the ID is defined as NOT NULL in the generated DB, so there should be a persistence exception or something else). Any ides why the sequence generator does not generate anything (I tried GenerationType.AUTO as well, but no difference)?

Answer 1

When you are doing entityManager.persist(registry) that is what it is going to do, store the Registry and check all the mappings for that class. It will encounter the collection of UserData objects, but because there is no cascade property matching the PERSIST it will not store the UserData objects.

It will only store the top level Registry object. If you want to change this add cascade={CascadeType.ALL} or at least cascade={CascadeType.PERSIST} to the @OneToMany annotation, to tell Hibernate it also needs to check the collection for new elements and persist those.

Or first store the UserData elements, before storing the Registry .