Thanks for your help Vivek.
Database Tables and rows:
'CREATE TABLE `device` (
 `device_id` int(11) NOT NULL AUTO_INCREMENT,
 `device_name` varchar(45) NOT NULL,
 `device_type_id` int(11) NOT NULL
 PRIMARY KEY (`device_id`),
 UNIQUE KEY `iddevice_UNIQUE` (`device_id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8'
INSERT INTO `mydb`.`device` (`device_id`, `device_name`, `device_type_id`) VALUES ('1', 'Test 1', '1');
INSERT INTO `mydb`.`device` (`device_id`, `device_name`, `device_type_id`) VALUES ('2', 'Test 2', '1');
CREATE TABLE `device_type` (
 `device_type_id` int(11) NOT NULL AUTO_INCREMENT,
 `type_name` varchar(45) NOT NULL,
 `subtype_name` varchar(45) NOT NULL,
 PRIMARY KEY (`device_type_id`),
 UNIQUE KEY `iddevice_type_UNIQUE` (`device_type_id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8
INSERT INTO `mydb`.`device_type` (`device_type_id`, `type_name`, `subtype_name`) VALUES ('1', 'Test Type', 'Test Subtype');
Entities:
@Entity
@Table(name = "device", schema = "mydb")
public class Device {
  @Id
  @Column(name = "device_id")
  private Integer id;
  @Column(name = "device_name")
  private String name;
  @ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
  @JoinColumn(name = "device_type_id")
  private DeviceType type;
  public Integer getId() {
    return id;
  }
  public void setId(Integer id) {
  }
  public String getName() {
    return name;
  }
  public void setName(String name) {
  }
  @Override
  public String toString() {
    return "Device {" +
        "id = " + id + "," +
        "name = " + name + "," +
        "type = " + type + "," +
        "}";
  }
}
@Entity
@Table(name = "device_type", schema = "mydb")
public class DeviceType {
  @Id
  @Column(name = "device_type_id")
  private int id;
  @Column(name = "type_name")
  private String type;
  @Column(name = "subtype_name")
  private String subtype;
  public int getId() {
    return id;
  }
  public void setId(int id) {
  }
  public String getType() {
    return type;
  }
  public void setType(String type) {
    this.type = type;
  }
  public String getSubtype() {
    return subtype;
  }
  public void setSubtype(String subtype) {
    this.subtype = subtype;
  }
  @Override
  public String toString() {
    return "DeviceType {" +
        "id = " + id + "," +
        "type = " + type + "," +
        "subtype = " + subtype +
        "}";
  }
}
Persistence:
       version="2.0">
  <persistence-unit name="maria_pu">
    <provider>com.impetus.kundera.KunderaPersistence</provider>
    <class>dev.model.Device</class>
    <class>dev.model.DeviceType</class>
    <properties>
      <property name="kundera.client.lookup.class" value="com.impetus.client.rdbms.RDBMSClientFactory" />
      <property name="hibernate.show_sql" value="true" />
      <property name="hibernate.format_sql" value="true" />
      <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5InnoDBDialect"/>
      <property name="hibernate.connection.driver_class" value="org.mariadb.jdbc.Driver" />
      <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/mydb" />
      <property name="hibernate.connection.username" value="root" />
      <property name="hibernate.current_session_context_class" value="thread"/>
      <!--<property name="hibernate.connection.password" value="impetus" />-->
      <!-- If using hibernate 3, use this:
      <property name="hibernate.current_session_context_class" value="org.hibernate.context.ThreadLocalSessionContext" />-->
      <!--<property name="hibernate.current_session_context_class" value="org.hibernate.context.internal.ThreadLocalSessionContext" />-->
    </properties>
  </persistence-unit>
  <persistence-unit name="cassandra_pu">
    <provider>com.impetus.kundera.KunderaPersistence</provider>
    <properties>
      <property name="kundera.nodes" value="localhost"/>
      <property name="kundera.port" value="9160"/>
      <property name="kundera.keyspace" value="environmentkeyspace"/>
      <property name="kundera.dialect" value="cassandra"/>
      <property name="kundera.client.lookup.class" value="com.impetus.client.cassandra.pelops.PelopsClientFactory" />-->
      <property name="kundera.client.lookup.class"  value="com.impetus.client.cassandra.thrift.ThriftClientFactory" />
    </properties>
  </persistence-unit>
</persistence>
Code that causes the problem:
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("maria_pu");
    EntityManager em = emf.createEntityManager();
    try {
          Device device = em.find(Device.class, 1);
          System.out.println(device);
    } catch (Exception e) {
      System.out.println("Something bad happened!");
      e.printStackTrace();
    } finally {
      em.close();
      emf.close();
    }
Expected output:
Device {id = 1,name = Test 1,type = DeviceType {id = 1,type = Test Type,subtype = Test Subtype},}
Thanks,
MK