Many-to-Many Properties

GarrettD78 · **Joined:** Fri May 05, 2006 12:09 am **Posts:** 11

I think I may have mapped these wrong but I can't figure out a good way of doing it. I have a many to many relationship of a Vehicle and Inspections. There are multiple Vehicles that each can have different inspections. The problem is I need an expiration date on the associate table so I can figure out when each Vehicle has an expired schedule. I am wondering if there is a better way that to create a separate collectioin and then have to programmatically figure out which inspection goes with a vehicle and then get the LastChecked date.

Vehicle(VehicleID,Make,Model)
Inspection(InspectionID,RegulatoryBody,InspectionName)
Vehicle_Inspection(VehicleID,InspectionID,Lastchecked)

Mapping Files

Code:

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0">

  <class name="FleetManagement.BusinessLayer.Inspection, FleetManagement.BusinessLayer" table="RegulatoryInspection">

    <id name="InspectionID" column="InspectionID" type ="String" length="50">
      <generator class="assigned" />
    </id>

    <property name="RegulatoryBody" />
    <property name="NameOfInspection" />
    <property name="TypeOfSchedule" />
    <property name="Period" />
    
    <set name="Vehicles" lazy="true" cascade="none" table="Vehicle_Schedule">
      <key column="InspectionID" />
      <many-to-many class="FleetManagement.BusinessLayer.Vehicle, FleetManagement.BusinessLayer" 
                   column="VehicleID" outer-join="auto" />
    </set>

    <bag name="Vehicle_Schedules" table="Vehicle_Schedule" lazy ="false" cascade="save-update">
      <key column="InspectionID" />

      <one-to-many class="FleetManagement.BusinessLayer.Vehicle_Schedule, FleetManagement.BusinessLayer" />

    </bag>

  </class>
</hibernate-mapping>

Code:

<?xml version="1.0" encoding="utf-8" ?>

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0">

  <class name="FleetManagement.BusinessLayer.Vehicle, FleetManagement.BusinessLayer" table="Vehicle">

    <id name="VehicleID" column="VehicleID" type="String" length="50">
      <generator class="assigned" />
    </id>

    <!--Mapp properties I'd like to be persist/fetch 
        Assume colum = property name-->
    <property name="UnitID" />
    <property name="Body_Type" />
    <property name="Make" />
    <property name="Model" />
    <property name="Year" />
    <property name="FunctionCode" />
    <property name="EnterpriseNO" />
    <property name="VIN" />
    <property name="Plate" />
    <property name="Location" />
    <property name="DriverName" />
    <property name="Description" />
    
    
    <bag name="Inspection" table="Vehicle_Inspections" lazy="false" cascade="save-update" >
      <key column="VehicleID" />
      <many-to-many class="FleetManagement.BusinessLayer.Inspection, FleetManagement.BusinessLayer"
                     column="InspectionID" outer-join="auto" /> 
    </bag>

    <bag name="Vehicle_Inspection" table="Vehicle_Inspection" lazy ="false" cascade="save-update">
      <key column="VehicleID" />
      
      <one-to-many class="FleetManagement.BusinessLayer.Vehicle_Inspections, FleetManagement.BusinessLayer" />
        
    </bag>

Code:

  <class name="FleetManagement.BusinessLayer.Vehicle_Inspection, FleetManagement.BusinessLayer" table="Vehicle_Inspection">

    <composite-id name="VehicleInspectionID" class="FleetManagement.BusinessLayer.IVehicleinspectionID, FleetManagement.BusinessLayer">
        <key-property name="VehicleID" />
        <key-property name="InspectionID" />
    </composite-id>

    <property name="LastChecked" />
    <property name="NextCheckDate" />
    
    
  </class>

tenwit · **Joined:** Thu Dec 23, 2004 9:08 pm **Posts:** 2008

Remove the Vehicles collection from Inspection, so that Inspection contains only a set of VehicleInspections (one-to-many). Change the composite-id of VehicleInspections to

Code:

<composite-id name="VehicleInspectionID" class="FleetManagement.BusinessLayer.IVehicleinspectionID, FleetManagement.BusinessLayer">
    <key-many-to-one name="Inspection" column="InspectionID" class="Inspection"/>
    <key-many-to-one name="Vehicle" column="VehicleID" class="Vehicle"/>
</composite-id>

Change your VehicleInspectionID implementation class accordingly, so that it contains a Vehicle and Inspection, instead their IDs. Then you can use code like (excuse the javaness, I don't speak Microsoft)

Code:

for (VehicleInspection vi : inspection.getVehicleInspections())
{
  Vehicle v = vi.getVehicleInspectionID().getVehicle();
  Date lastChecked = vi.getLastChecked();
  // Your code...
}

Obviously, putting a getVehicle() method into Inspection (that returns getVehicleInpsectionID().getVehicle()) would be a good thing.

GarrettD78 · **Joined:** Fri May 05, 2006 12:09 am **Posts:** 11

Thanks tenwit that worked perfect. Did not know I could do the composite keys like that. I think I am still thinking in terms of tables instead on objects.