CREATE  TABLE Towers (
  Id INT NOT NULL AUTO_INCREMENT ,
  Name VARCHAR(5) NOT NULL ,
  PRIMARY KEY (Id));

CREATE  TABLE LineOfBusiness (
  Id INT NOT NULL AUTO_INCREMENT,
  Name VARCHAR(15) NOT NULL ,
  PRIMARY KEY (Id));

CREATE  TABLE LineOfBusinessXTowers (
  LineOfBusinessId INT NOT NULL ,
  TowerId INT NOT NULL ,
  PRIMARY KEY (LineOfBusinessId, TowerId));

CREATE  TABLE IF NOT EXISTS Departments (
  Code INT NOT NULL ,
  LineOfBusinessId INT NOT NULL ,
  TowerId INT NOT NULL ,
  PRIMARY KEY (Code));

ALTER TABLE LineOfBusinessXTowers
  ADD CONSTRAINT FK_LineOfBusinessXTowers_LineOfBusiness
    FOREIGN KEY (LineOfBusinessId)
    REFERENCES LineOfBusiness (Id)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION,
  ADD CONSTRAINT FK_LineOfBusinessXTowers_Towers
    FOREIGN KEY (TowerId)
    REFERENCES Towers (Id)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION;

ALTER TABLE Departments
  ADD CONSTRAINT FK_Departments_LineOfBusinessXTowers
    FOREIGN KEY (LineOfBusinessId, TowerId)
    REFERENCES LineOfBusinessXTowers (LineOfBusinessId,TowerId)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION;

public class Departments {
        private int code;
   private String name;
   private LineOfBusiness lineOfBusiness;
   private Towers tower;

       //Constructors and access methods here
}

<hibernate-mapping>
   <class name="Departments" table="Departments" catalog="DB">
      <id name="code" type="int">
         <column name="Code" />
         <generator class="assigned" />
      </id>
      <property name="name" type="string">
         <column name="Name" length="45" not-null="true" unique="true" />
      </property>

      <join table="LineOfBusinessXTowers" optional="false">
         <key column="LineOfBusinessId" unique="false" />
         <many-to-one name="lineOfBusiness"
            class="LineOfBusiness">
            <column name="LineOfBusinessId" not-null="true" />
         </many-to-one>
      </join>
      <join table="LineOfBusinessXTowers" optional="false">
         <key column="TowerId" unique="false" />
         <many-to-one name="towers" class="Towers">
            <column name="TowerId" not-null="true" />
         </many-to-one>
      </join>
   </class>
</hibernate-mapping>