# Annotation Exception: @OneToOne or @ManyToOne

**URL:** <https://discourse.hibernate.org/t/annotation-exception-onetoone-or-manytoone/4427>\
**Category:** Hibernate ORM\
**Created:** [July 27, 2020, 8:28am UTC](https://discourse.hibernate.org/t/annotation-exception-onetoone-or-manytoone/4427 "2020-07-27T08:28:35Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![jfa\_gyaana](https://avatars.discourse-cdn.com/v4/letter/j/e495f1/32.png) [@jfa\_gyaana](https://discourse.hibernate.org/u/jfa_gyaana)\
**Post date:** [July 27, 2020, 8:28am UTC](https://discourse.hibernate.org/t/annotation-exception-onetoone-or-manytoone/4427/1 "2020-07-27T08:28:35Z")

</div>

I have the following tables in Db2.

```auto
CREATE TABLE DB2ADMIN.School (school_id SMALLINT PRIMARY KEY NOT NULL, name varchar(128));

create table DB2ADMIN.Student (student_id int PRIMARY KEY NOT null, name varchar(128) not null, age smallint not null, school_id int NOT NULL, FOREIGN KEY (school_id) REFERENCES School(school_id));

```

I can successfully insert records into the tables using the Db2 console.

```auto
INSERT INTO db2admin.school VALUES (1, 'BJS');

INSERT INTO db2admin.STUDENT VALUES (1, 'Pankaj', 30, 1);

```

One School can contain many students. Here is how I am defining the entity relationships in Hibernate 5.4.18.

```auto
@Entity
@Table(name = "school")
public class School
{
    @Id
    @SequenceGenerator(name = "SchoolIdSequence", schema="db2admin", sequenceName = "Sequence_School", allocationSize = 1)
    @GeneratedValue(generator = "SchoolIdSequence", strategy = GenerationType.SEQUENCE)
    @Column(name = "SCHOOL_ID")
    private int id;

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

    @OneToMany(fetch = FetchType.LAZY, cascade=CascadeType.ALL, mappedBy = "school")
    //@JoinColumn(name="student_id", nullable=false)
    private Set<Student> students;

    public School()
    {}

    public School(String name)
    {
        this.name = name;
    }

    public int getId()
    {
        return id;
    }

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

    public String getName()
    {
        return name;
    }

    public void setName(String name)
    {
        this.name = name;
    }
    
    public Set getStudents()
    {
        return students;
    }
 
    public void setStudents(Set students)
    {
        this.students = students;
    }

    @Override
    public String toString()
    {
        return "School [Name = '" + name + "']";
    }
}

@Entity
@Table(name = "student")
public class Student
{
    @Id
    @SequenceGenerator(name = "SequenceStudentId", sequenceName = "Sequence_Student", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SequenceStudentId")
    @Column(name = "STUDENT_ID")
    private int id;

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

    @Column(name = "AGE")
    private int age;

    @ManyToOne(cascade=CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinColumn(name="school_id", nullable=false)
    private School school;
    
    public Student() 
    {}

    public Student(String name, int age, School school)
    {
        this.name = name;
        this.age = age;
        this.school = school;
    }

    public int getId()
    {
        return id;
    }

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

    public String getName()
    {
        return name;
    }

    public void setName(String name)
    {
        this.name = name;
    }

    public int getAge()
    {
        return age;
    }

    public void setAge(int age)
    {
        this.age = age;
    }

    @Override
    public String toString()
    {
        return "Student [id=" + id + ", Name=" + name + ", Age=" + age + "]";
    }
}

```

I get the following error on executing the application.

```auto
org.hibernate.AnnotationException: @OneToOne or @ManyToOne on org.jfa.persistence.hibernate.entity.Student.school references an unknown entity: org.jfa.persistence.hibernate.entity.School

```

I have tried to tweak the relationship settings in the class in different ways as suggested by others on Internet/StackOverFlow. Yet, no luck so far. Please help.