Hibernate problem - "Use of @OneToMany or @ManyToMany targeting an unmapped class"

I'm finding my feet with Hibernate Annotations and I've hit a problem I hope someone can help with.

I have 2 entities, Section and ScopeTopic. The section has a List class member, so a One to Many relationship. When I run my unit test I am getting this exception:

> Use of @OneToMany or @ManyToMany targeting an unmapped class: com.xxx.domain.Section.scopeTopic[com.xxx.domain.ScopeTopic]

I would assume that the error implies that my ScopeTopic entity isn't mapped to a table? I can't see with I have done wrong. Here are the Entity classes:

---

@Entity
public class Section {
    private Long id;
    private List<ScopeTopic> scopeTopics;

    public Section() {}

    @Id
    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    @OneToMany
    @JoinTable(name = "section_scope", joinColumns = {@JoinColumn(name="section_id")},
               inverseJoinColumns = {@JoinColumn(name="scope_topic_id")} )
    public List<ScopeTopic> getScopeTopic() {
        return scopeTopic;
    }

    public void setScopeTopic(List<ScopeTopic> scopeTopic) {
        this.scopeTopic = scopeTopic;
    }
}

---

@Entity
@Table(name = "scope_topic")
public class ScopeTopic {
    private Long id;
    private String topic;

    public ScopeTopic() {}

    @Id
    public Long getId() {
        return id;
    }

    public void setId() {
        this.id = id;
    }

    public String getTopic() {
        return topic;
    }

    public void setTopic(String topic) {
        this.topic = topic;
    }
}

---

I'm pretty sure it's my own lack of understanding that's at fault so some guidance would be great, thanks!

Your annotations look fine. Here are the things to check:

• make sure the annotation is javax.persistence.Entity, and not org.hibernate.annotations.Entity. The former makes the entity detectable. The latter is just an addition.

• if you are manually listing your entities (in persistence.xml, in hibernate.cfg.xml, or when configuring your session factory), then make sure you have also listed the ScopeTopic entity

• make sure you don't have multiple ScopeTopic classes in different packages, and you've imported the wrong one.

Mine was not having @Entity on the many side entity

@Entity // this was commented
@Table(name = "some_table")
public class ChildEntity {
    @JoinColumn(name = "parent", referencedColumnName = "id")
    @ManyToOne
    private ParentEntity parentEntity;
}

Your entity may not listed in hibernate configuration file.

Mostly in Hibernate , need to add the Entity class in hibernate.cfg.xml like-

<hibernate-configuration>
  <session-factory>

    ....
    <mapping class="xxx.xxx.yourEntityName"/>
 </session-factory>
</hibernate-configuration>

If you are using Java configuration in a spring-data-jpa project, make sure you are scanning the package that the entity is in. For example, if the entity lived com.foo.myservice.things then the following configuration annotation below would not pick it up.

You could fix it by loosening it up to just com.foo.myservice (of course, keep in mind any other effects of broadening your scope to scan for entities).

@Configuration
@EnableJpaAuditing
@EnableJpaRepositories("com.foo.myservice.repositories")
public class RepositoryConfiguration {
}

In my case a has to add my classes, when building the SessionFactory, with addAnnotationClass

Configuration configuration.configure();
StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties());
SessionFactory sessionFactory = configuration
            .addAnnotatedClass(MyEntity1.class)
            .addAnnotatedClass(MyEntity2.class)
            .buildSessionFactory(builder.build());

I had the same problem and I could solve it by adding the entity into persistence.xml. The problem was caused due to the fact that the entity was not added to the persistence config. Edit your persistence file:

<persistence-unit name="MY_PU" transaction-type="RESOURCE_LOCAL">
<provider>`enter code here`
     org.hibernate.jpa.HibernatePersistenceProvider
  </provider>
<class>mypackage.MyEntity</class>

...

-First Check you put the @Entity and top of all Models

-Second Check the @Table(name=" table_name ") with the correct table_name

-Third Check you add the Entity class in hibernate.cfg.xml or persistence.configuration

this error usually comes from above failure.

Check the package structure for the @Entity classes.

I also faced an similar issue which occurred as I accidental misspelled the package name.

Make sure all you @Entity classes are under the package(folder) within or below the package of Class having your main() function, as the SpringBootApplication will scan only on and inside the same package.

In case your @Entity Class is not getting scanned, it will not be Mapped, and will give the mentioned error.

You can also check if your @Entity class is getting mapped or scanned correctly by checking the Database. Whenever a Class is marked as @Entity, a table is automatically generated by Hibernate/JPA in the applicable database.

I got the same error in this case:

was:

@ElementCollection(targetClass=**String**.class)
@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(name = "user_roles",
        joinColumns = @JoinColumn(name = "user_id"),
        inverseJoinColumns = @JoinColumn(name = "role_id"))
private Set<Role> authorities = new HashSet<>();

Fixed to:

@ElementCollection(targetClass=**Role**.class)
@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(name = "user_roles",
        joinColumns = @JoinColumn(name = "user_id"),
        inverseJoinColumns = @JoinColumn(name = "role_id"))
private Set<Role> authorities = new HashSet<>();