create table TblLocation
(
  id number(38,0) not null,
  name varchar2(255) not null,
  primary key (id)
);

create table TblItem
(
  id number(38,0) not null,
  name varchar2(255) not null,
  primary key (id)
);

create table TblInventoryItem
(
  location_id number(38,0) not null,
  item_id number(38,0) not null,
  quantity number(38,0) not null,
  price number(38,2) not null,
  primary key (location_id,item_id),
  foreign key (location_id) references TblLocation(id),
  foreign key (item_id) references TblItem(id)
);

@Entity
@Table(name="TblLocation")
@SequenceGenerator(name="LocationSeq",sequenceName="LOCATION_SEQ")
public class Location
{
   private long id;
   private String name;
   private Set<InventoryItem> _items;
   
   @Id
   @GeneratedValue(strategy=GenerationType.SEQUENCE,generator="LocationSeq")
   public long getId()
   {
      return id;
   }
   
   public void setId(long id)
   {
      this.id = id;
   }
   
   public String getName()
   {
      return name;
   }
   
   public void setName(String name)
   {
      this.name = name;
   }

   @OneToMany(mappedBy="location")
   public Set<InventoryItem> getItems()
   {
      return _items;
   }

   public void setItems(Set<InventoryItem> items)
   {
      _items = items;
   }
}


@Entity
@Table(name="TblItem")
@SequenceGenerator(name="ItemSeq",sequenceName="ITEM_SEQ")
public class Item
{
   private long id;
   private String name;
   
   @Id
   @GeneratedValue(strategy=GenerationType.SEQUENCE,generator="ItemSeq")
   public long getId()
   {
      return id;
   }
   
   public void setId(long id)
   {
      this.id = id;
   }
   
   public String getName()
   {
      return name;
   }
   
   public void setName(String name)
   {
      this.name = name;
   }
}


@Entity
@Table(name="TblInventoryItem")
@IdClass(InventoryItemId.class)
public class InventoryItem
{
   private Location _location;
   private Item _item;
   private long _quantity;
   private float _price;
   
   @Id
   @ManyToOne
   @JoinColumn(name="location_id")
   public Location getLocation()
   {
      return _location;
   }
   
   public void setLocation(Location location)
   {
      _location = location;
   }
   
   @Id
   @ManyToOne
   @JoinColumn(name="item_id")
   public Item getItem()
   {
      return _item;
   }
   
   public void setItem(Item item)
   {
      _item = item;
   }
   
   public float getPrice()
   {
      return _price;
   }
   
   public void setPrice(float price)
   {
      _price = price;
   }
   
   public long getQuantity()
   {
      return _quantity;
   }
   
   public void setQuantity(long quantity)
   {
      _quantity = quantity;
   }
}

@Embeddable
public class InventoryItemId
{
   private Location   _location;
   private Item      _item;
   
   public Item getItem()
   {
      return _item;
   }
   public void setItem(Item item)
   {
      _item = item;
   }
   public Location getLocation()
   {
      return _location;
   }
   public void setLocation(Location location)
   {
      _location = location;
   }
}

 
  @Entity
  @Table(name = "Product")
  public class Product extends AbstractRecordImpl
  {
    @NotNull private String name;
    private String description;
   
    //Some getters & setters
    ...
  }
 
  @Entity
  @Table(name = "Item")
  public class Item extends AbstractRecordImpl
  {
    @NotNull private String name;

    //Some getters & setters
    ...
  }

  @Entity
  @Table(name = "ProductItem")
  public class ProductItem
  {
    @Id
    private ProductItemPK primaryKey = new ProductItemPK();
    private String description;

    public String getDescription() {
      return description;
    }

    public void setDescription(String description) {
      this.description = description;
    }

    //needed for hibernate
    public void setPrimaryKey(ProductItemPK primaryKey) {
      this.primaryKey = primaryKey;
    }

    public void setProduct(Product product) {
      primaryKey.setProduct(product);
    }

    public Product getProduct(){
      return primaryKey.getProduct();
    }

    public void setItem(Item item) {
      primaryKey.setItem(item);
    }

    public Item getItem() {
      return primaryKey.getItem();
    }


    @Embeddable
    private class ProductItemPK implements Serializable
    {
      @ManyToOne
      private Item item;

      @ManyToOne
      private Product product;

      public ProductItemPK() {}

      //Some getters and setters
      ...
    }
  }

  @OneToMany(mappedBy="primaryKey")
  private List<ProductItem> productItems = new ArrayList<ProductItem>();

Location location = (Location)session.get(Location.class, new Long(1));
Set<InventoryItem> items = location.getItems();
for(InventoryItem item : items)
{
    .... access InventoryItems here ...
}

<class
    name="Location"
    table="TblLocation">

    <id name="id" type="long" column="ID" >
        <generator class="sequence">
            <param name="sequence">LOCATION_SEQ</param>
        </generator>
    </id>

    <property
        name="name"
        type="java.lang.String"
        column="NAME"
        not-null="true"
        length="255">
    </property>

    <!-- associations -->
    <set name="items" inverse="true" fetch="join" cascade="save-update">
        <key column="location_id"/>
        <one-to-many class="InventoryItem"/>
    </set>
</class>


<class
    name="Item"
    table="TblItem"
    lazy="false">

    <id name="id" type="long" column="ID" >
        <generator class="sequence">
            <param name="sequence">ITEM_SEQ</param>
        </generator>
    </id>

    <property
        name="name"
        type="java.lang.String"
        column="NAME"
        not-null="true"
        length="255">
    </property>
</class>

<class
    name="InventoryItem"
    table="TblInventoryItem"
    lazy="false">

    <composite-id name="id" class="InventoryItemId">
        <key-many-to-one
            name="location"
            class="Location"
            column="location_id"/>
        <key-many-to-one
            name="item"
            class="Item"
            column="item_id"/>
    </composite-id>

    <property name="quantity" type="long" column="quantity" not-null="true"/>
    <property name="price" type="float" column="price" not-null="true"/>
</class>

property not found: location on entity InventoryItem

@Entity
@Table(name="TblInventoryItem")
public class InventoryItem
{
   private InventoryItemId _id;
   private long _quantity;
   private float _price;

   @EmbeddedId
   public InventoryItemId getId()
   {
      return _id;
   }
   ... other getters and setters ...
}

@Embeddable
public class InventoryItemId implements Serializable
{
   private Location   _location;
   private Item      _item;
   
   @ManyToOne
   @JoinColumn(name="item_id",nullable=false)
   public Item getItem()
   {
      return _item;
   }
   
   @ManyToOne
   @JoinColumn(name="location_id",nullable=false)
   public Location getLocation()
   {
      return _location;
   }

   ... setters removed ...
}

@Column(name="item_id", nullable=false, updatable=false, insertable=false)
private Item item;