Hi,
I want to create a very simple one-to-one relationship between two
classes - 'Employee' and 'MedicalRecord' - i.e one employee has one
medical record. I have created two database tables - 'medicalrecord' and
'employee'. The 'employee' table has a primary key called 'employeeId'.
Medical records are linked to employees via a foreign key in the
'medicalrecord' table, also called 'employeeId'.
HERE ARE MY CLASS DEFINITIONS:-
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
public class MedicalRecord
{
private int medicalRecordId;
private int employeeId;
+ other fields
public int getMedicalRecordId() {
return medicalRecordId;
}
public void setMedicalRecordId(int theId) {
medicalRecordId = theId;
}
public int getEmployeeId()
{
return employeeId;
}
public void setEmployeeId(int theId) {
employeeId = theId;
}
+ other public accessor methods
}
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
public class Employee
{
private int employeeId;
private MedicalRecord medicalRecord;
+ other fields
public void setEmployeeId(int CustId) {
employeeId=CustId;
}
public int getEmployeeId() {
return employeeId;
}
public MedicalRecord getMedicalRecord() {
return medicalRecord;
}
public void setMedicalRecord(MedicalRecord mr) {
medicalRecord = mr;
}
+ other public accessor methods
}
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
HERE ARE MY MAPPINGS:-
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
<!-- Mapping for MedicalRecord -->
<class name="MedicalRecord" identity="medicalRecordId"
key-generator="IDENTITY">
<description MedicalRecord definition</description>
<map-to table="medicalrecord" xml="medicalrecord" />
<field name="medicalRecordId" type="integer">
<sql name="medicalRecordId" type="integer" />
<xml name="medicalRecordId" node="attribute"/>
</field>
<field name="employeeId" type="integer">
<sql name="employeeId" type="integer" />
<xml name="employeeId" node="attribute"/>
</field>
+ other field definitions
</class>
<!-- Mapping for Employee -->
<class name="Employee" identity="employeeId" key-generator="IDENTITY">
<description>Employee definition</description>
<map-to table="employee" xml="project" />
<field name="employeeId" type="integer">
<sql name="employeeId" type="integer" />
<xml name="employeeId" node="attribute"/>
</field>
<field name="medicalRecord" type="MedicalRecord">
<sql name="employeeId" />
<xml name="medicalRecord" node="element" />
</field>
+ other field definitions
</class>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Here is a code snippet that first retrieves a specific Employee, creates
a new MedicalRecord, links it to the Employee, and then persists it:-
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Employee employee;
MedicalRecord medicalRecord;
OQLQuery employeeOql;
QueryResults employees;
employeeOql = db.getOQLQuery("SELECT e from Employee e WHERE
employeeId=$1");
employeeOql.bind(53);
employees = employeeOql.execute();
while(employees.hasMore()) {
employee = (Employee)employees.next();
// Create a new MedicalRecord object associated with the
Employee and persist it
medicalRecord = new MedicalRecord();
medicalRecord.setEmployeeId(employee.getEmployeeId());
+ set other medicalRecord properties
db.create(medicalRecord);
}
db.commit(); // Line of code that throws exception.
db.close();
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Execution of this code results in the following stack trace:-
java.sql.SQLException: [SQLDEV]Column name 'employeeId' appears more
than once in the result column list. at com.inet.tds.a.a(Unknown Source)
at com.inet.tds.b.do(Unknown Source) at
com.inet.tds.b.executeUpdate(Unknown Source) at
org.exolab.castor.jdo.engine.SQLEngine.store(SQLEngine.java:849) at
org.exolab.castor.persist.ClassMolder.store(ClassMolder.java:1544) at
org.exolab.castor.persist.LockEngine.store(LockEngine.java:745) at
org.exolab.castor.persist.TransactionContext.prepare(TransactionContext.java:1162)
at
org.exolab.castor.jdo.engine.DatabaseImpl.commit(DatabaseImpl.java:498)
at
com.fc.fortunecookie.servlets.EmployeeServlet.service(EmployeeServlet.java:104)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853) at
org.apache.tomcat.core.ServletWrapper.handleRequest(ServletWrapper.java:503)
at
org.apache.tomcat.core.ContextManager.service(ContextManager.java:559)
at
org.apache.tomcat.service.http.HttpConnectionHandler.processConnection(HttpConnectionHandler.java:160)
at
org.apache.tomcat.service.TcpConnectionThread.run(SimpleTcpEndpoint.java:338)
at java.lang.Thread.run(Thread.java:484)
The line in the trace
"com.fc.fortunecookie.servlets.EmployeeServlet.service(EmployeeServlet.java:104)"
corresponds to the "db.commit()" line of code above, which is causing
the exception.
Can anyone tell me if I am going about this relation in the right way in
terms of my class mapping ? I am doing something fundamentally wrong or
missing something here ?
Am I right to use:
<field name="medicalRecord" type="MedicalRecord">
<sql name="employeeId" />
<xml name="medicalRecord" node="element" />
</field>
in my mapping file ?
I have other 1:1 relations set up in the same way inside my Employee
mapping that also use "employeeId" primary/foreign key relationship to
link together the tables (in this case 'employee' with 'bankaccount'.
For example:
<field name="bankAccount" type="com.fc.fortunecookie.beans.BankAccount">
<sql name="employeeId" />
<xml name="bankAccount" node="element" />
</field>
I can get one-to-many relationships working no problem but can't seem to
get any of my 1:1 mappings to work (i.e. to commit). Can I only use the
"employeeId" foreign key name once in another (i.e. not 'employee')
table ?
Any help would be greatly appreciated.
Regards,
Graeme
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