Many-to-one associations for Hibernate

message2hero · **Joined:** Wed Mar 28, 2007 2:23 pm **Posts:** 4

Hi,

I am using Hibernate 3.0 . I need help on retriving info from database where tables are associated with many-to-one relationship.

I have read about an attribute "formula" which will deal with many-to-one relation, but I have no clue how to use. Could anyone help me on this.

Thanks,
message2hero

anandbn · **Posted:** Fri Apr 20, 2007 11:41 am

Formula and <many-to-one> relationships are two diferrent things. Please specify the table strcutures that you are trying to retrieve and we can help further.

Here's a simple example of bi-directional many-to-one:

Code:

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
   "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
   "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping 
   package="com.test.hibernate.model">

   <class name="Employee" table="EMPLOYEE">
      
      <id name="employeeId" column="EMPLOYEE_ID" unsaved-value="-1">
         <generator class="increment"/>
      </id>
      
      <property name="firstName" column="FIRST_NAME"
              not-null="true"
              length="20"
              />
      <property name="lastName" column="LAST_NAME"
              length="20"
              />
      <property name="address1" column="ADDRESS_1"
              length="20"
              />
      <property name="address2" column="ADDRESS_2"
              length="20"
              />
      <property name="zipCode" column="ZIP_CODE"
              length="20"
              />
      <property name="fullName" formula="FIRST_NAME||LAST_NAME"
              length="20"
              />              
   
      <set name="empHistory" cascade="all" >
         <key column="EMPLOYEE_ID"/>
         <one-to-many class="EmployeeHistory" inverse="true"/>
      </set>
   </class>
   
</hibernate-mapping>

Code:

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
   "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
   "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping 
   package="com.test.hibernate.model">

   <class name="EmployeeHistory" table="EMPLOYEE_HISTORY">
      
      <id name="eventId" column="EVENT_ID">
         <generator class="increment"/>
      </id>
      
      <property name="dateOccurred" column="OCCURRED_DT" not-null="true" />
      <property name="eventType" column="EVENT_TYPE"/>
      <property name="comments" column="COMMENTS"/>
      <many-to-one name="employee" />
   </class>
   
</hibernate-mapping>

[/code]

message2hero · **Joined:** Wed Mar 28, 2007 2:23 pm **Posts:** 4

Hi,

Below is confg file which has FACILITY_ID as primary key from FACILITY.

<class name="htm.dto.Facility" table="FACILITY" schema="dbo" catalog="Aviation">
<id name="facilityId" type="integer">
<column name="FACILITY_ID" />
<generator class="assigned" />
</id>
<many-to-one name="dotDistrict" class="htm.dto.DotDistrict" fetch="select">
<column name="DOT_DIST_ID" />
</many-to-one>

Below is second config file file which has RUNWAY_ID as primary one. It is associated as many-to-one with FACILITYtable .

<hibernate-mapping>
<class name="htm.dto.Runway" table="RUNWAY" schema="dbo" catalog="Aviation">
<id name="runwayId" type="integer">
<column name="RUNWAY_ID" />
<generator class="assigned" />
</id>
<many-to-one name="facility" class="htm.dto.Facility" fetch="select">
<column name="FACILITY_ID" not-null="true" />
</many-to-one>
<many-to-one name="surfaceTreatment" class="htm.dto.SurfaceTreatment" fetch="select">
<column name="SURFACE_TREATMENT_ID" />
</many-to-one>
<many-to-one name="surfaceType" class="htm.dto.SurfaceType" fetch="select">
<column name="SURFACE_TYPE_ID" />
</many-to-one>
<property name="runwayRecordType" type="string">
<column name="RUNWAY_RECORD_TYPE" length="3" />
</property>
<set name="runwayEnds" inverse="true">
<key>
<column name="RUNWAY_ID" not-null="true" />
</key>
<one-to-many class="htm.dto.RunwayEnd" />
</set>
</class>
</hibernate-mapping>

So, how can i get the values from RUNWAY table if know the FACILITY_ID which is primary key for FACILITY table.

Beloy is my class file:

int facilityId = facility.getFacilityId();
System.out.println("Facility Id" + facilityId); //here facilityId value is available and passing it to query to gwt the values from Runway table associated with Facility table
runwayEnd = (RunwayEnd) session.createQuery(" from Runway R where R.facility.facilityId=:facilityId").setInteger("facilityId", facilityId).uniqueResult();

Thanks,
message2hero

message2hero · **Joined:** Wed Mar 28, 2007 2:23 pm **Posts:** 4

[quote="message2hero"]Hi,

Below is confg file which has FACILITY_ID as primary key from FACILITY.

<class name="htm.dto.Facility" table="FACILITY" schema="dbo" catalog="Aviation">
<id name="facilityId" type="integer">
<column name="FACILITY_ID" />
<generator class="assigned" />
</id>
<many-to-one name="dotDistrict" class="htm.dto.DotDistrict" fetch="select">
<column name="DOT_DIST_ID" />
</many-to-one>

Below is second config file file which has RUNWAY_ID as primary one. It is associated as many-to-one with FACILITYtable .

<hibernate-mapping>
<class name="htm.dto.Runway" table="RUNWAY" schema="dbo" catalog="Aviation">
<id name="runwayId" type="integer">
<column name="RUNWAY_ID" />
<generator class="assigned" />
</id>
<many-to-one name="facility" class="htm.dto.Facility" fetch="select">
<column name="FACILITY_ID" not-null="true" />
</many-to-one>
<many-to-one name="surfaceTreatment" class="htm.dto.SurfaceTreatment" fetch="select">
<column name="SURFACE_TREATMENT_ID" />
</many-to-one>
<many-to-one name="surfaceType" class="htm.dto.SurfaceType" fetch="select">
<column name="SURFACE_TYPE_ID" />
</many-to-one>
<property name="runwayRecordType" type="string">
<column name="RUNWAY_RECORD_TYPE" length="3" />
</property>
<set name="runwayEnds" inverse="true">
<key>
<column name="RUNWAY_ID" not-null="true" />
</key>
<one-to-many class="htm.dto.RunwayEnd" />
</set>
</class>
</hibernate-mapping>

So, how can i get the values from RUNWAY table if know the FACILITY_ID which is primary key for FACILITY table.

Beloy is my class file:

int facilityId = facility.getFacilityId();
System.out.println("Facility Id" + facilityId);
runwayEnd = (RunwayEnd) session.createQuery(" from Runway R where R.facility.facilityId=:facilityId").setInteger("facilityId", facilityId).uniqueResult();

Thanks,
Hero

anandbn · **Posted:** Fri Apr 20, 2007 3:05 pm

Could you post the SQL queries generated while running the code? Are you getting exceptions?

Ananasi · **Posted:** Fri Apr 20, 2007 4:06 pm

Try this for your HQL:

"from Runway R where R.facility.id=:facilityId"

You may need a join in there, not sure.