Many-to-one throw not-null exception

Hibernate ORM
1

I have three tables with the following structure

CREATE TABLE users (
    ID INT AUTO_INCREMENT,
    FIRSTNAME VARCHAR(100) NOT NULL,
    LASTNAME VARCHAR(100) NOT NULL,
    AGE INT NOT NULL,
    ID_ROLE INT NOT NULL,
    ID_LEVEL INT NOT NULL,
    PRIMARY KEY (ID)
);
CREATE TABLE roles (
    ID INT AUTO_INCREMENT,
    ROLE VARCHAR(100) NOT NULL,
);
CREATE TABLE levels (
    ID INT AUTO_INCREMENT,
    LEVEL VARCHAR(100) NOT NULL,
);

The users table is related to the roles and levels tables through foreign key ID_ROLE and ID_LEVEL (Both refer to the ID fields). In Java I have three classes that I would mapping on these tables with Hibernate. I using the XML configuration file. The three classes look like this:

public class User {
    int id, age;
    private String firstname, lastname;
    private Role ref_role;
    private Level ref_level;

    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getFirstName() {
        return firstname;
    }
    public void setFirstName(String firstname) {
        this.firstname= firstname;
    }
    public String getLastName() {
        return lastname;
    }
    public void setLastName(String lastname) {
        this.lastname= lastname;
    }
    public Ruolo getRef_role() {
        return ref_role;
    }
    public void setRef_role(Role ref_role) {
        this.ref_ruolo = ref_ruolo;
    }
    public Livello getRef_level() {
        return ref_level;
    }
    public void setRef_level(Level ref_level) {
        this.ref_level= ref_level;
    }
    public User() {}
}
public class Role {
    private int id;
    private String role;

    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getRole() {
        return role;
    }
    public void setRole(String role) {
        this.role = role;
    }
    public Role() {
    }
}
public class Level {
    private int id;
    private String level;

    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getLevel() {
        return level;
    }
    public void setLevel(String level) {
        this.level = level;
    }
    public Level() {}
}

The configuration file of hibernate is follows:

<hibernate-configuration>
    <session-factory>
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/mydatabase</property>
        <property name="connection.username">root</property>
        <property name="connection.password"></property>
        <property name="hibernate.c3p0.min_size">5</property>
        <property name="hibernate.c3p0.max_size">20</property>
        <property name="hibernate.c3p0.timeout">300</property>
        <property name="hibernate.c3p0.max_statements">50</property>
        <property name="hibernate.c3p0.idle_test_period">3000</property>

        <mapping resource="user.hbm.xml"/>
        <mapping resource="role.hbm.xml"/>
        <mapping resource="level.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

As for the mapping files I have the following files
For User class (in user.hbm.xml file):

<hibernate-mapping>
    <class name="User" table="users">
        <id name="id" column="ID" type="integer">
            <generator class="native"/>
        </id>
        <property name="firstname" column="FIRSTNAME" type="string"/>
        <property name="lastname" column="LASTNAME" type="string"/>
        <property name="age" column="AGE" type="integer"/>

        <many-to-one name="ref_role" class="Role" column="ID_ROLE" not-null="true"/>
        <many-to-one name="ref_level" class="Level" column="ID_LEVEL" not-null="true"/>
    </class>
</hibernate-mapping>

The Role class mapping is in role.hbm.xml file:

<hibernate-mapping>
    <class name="Role" table="roles">
        <id name="id" column="ID" type="integer">
            <generator class="native"/>
        </id>
        <property name="role" column="ROLE" type="string"/>
    </class>
</hibernate-mapping>

The Level class mapping is in level.hbm.xml file:

<hibernate-mapping>
    <class name="Level" table="levels">
        <id name="id" column="ID" type="integer">
            <generator class="native"/>
        </id>
        <property name="level" column="LEVEL" type="string"/>
    </class>
</hibernate-mapping>

It get me problem with two many-to-one relationship, whereas with only one it work fine. With two many-to-one relationship the application throw me the follow exception.

org.hibernate.PropertyValueException: not-null property references a null or transient value : model.User.ref_level

Do you know how I can solve it and why does it give me this exception?

2

Maybe you didn’t set the model.User.ref_level property.

3

indeed it is so :sweat_smile: I’ve been there days on it and I didn’t notice that the error was those, I thought that was an error of mapping. Thanks for the help me. :slight_smile:

4

You’re welcome. I’m glad I could help.