Hi Adam,
Adam Brons wrote:
Hey Everyone,
I have a question about mapping inheritance.
What I'm having trouble doing is reading and updating a collection of a
subclasses. It writes the Manager entry with the Manager => Employee
mapping without problem. Unfortunately when I read in the Company class
and it loads a collection of employees it does not collect the Manager =>
Employee mapping. Based on the method of Inheritance I used I was under
the impression that OJB would use the class listed in ojbConcreteClass
(class_name) as the class to load the data into, and since that class in
some cases is a Manager, it should load and populate the Manager's
Collection of Employees.
Any help you can offer would be most appreciated. Thank!
I think you mixed up two different inheritance strategies.
table per class
file:///E:/dev/db-ojb-1b/ojb/doc/docu/guides/advanced-technique.html#Mapping+Each+Class+of+a+Hierarchy+to+a+Distinct+Table+%28table+per+class%29
table per subclass
file:///E:/dev/db-ojb-1b/ojb/doc/docu/guides/advanced-technique.html#Mapping+Each+Subclass+to+a+Distinct+Table+%28table+per+subclass%29
You use a discriminator column to identify the real class (used in
"table per class"), but in your posted database table script it seems
you expect a "table per subclass" mapping.
Could this be the issue?
regards,
Armin
The following is an EXAMPLE of what I'm trying to do.
Classes --- Based on documentation examples:
==================================
public class Company {
private Integer id;
private Collection<Employee> employees;
private String name;
public Company() { }
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public Collection<Employee> getEmployees() {
if (employees == null)
employees = new ArrayList();
return employees;
}
public void setEmployees(Collection<Employee> employees) {
this.employees = employees;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
public class Employee {
protected Integer id;
protected Integer companyId;
protected String name;
protected String ojbConcreteClass;
public Employee() { this.ojbConcreteClass =
this.getClass().getName(); }
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public Integer getCompanyId() {
return companyId;
}
public void setCompanyId(Integer companyId) {
this.companyId = companyId;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getOjbConcreteClass() {
return ojbConcreteClass;
}
public void setOjbConcreteClass(String ojbConcreteClass) {
this.ojbConcreteClass = ojbConcreteClass;
}
}
public class Manager extends Employee {
private Collection<Employee> employees;
public Manager() { super(); }
public Collection<Employee> getEmployees() {
if (employees == null)
employees = new ArrayList();
return employees;
}
public void setEmployees(Collection<Employee> employees) {
this.employees = employees;
}
}
Database(DB2) tables:
================
CREATE TABLE company (
company_id INTEGER NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH 1
INCREMENT BY 1),
name varchar(255) NOT NULL,
--
PRIMARY KEY (company_id)
);
CREATE TABLE employee (
employee_id INTEGER NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH 1
INCREMENT BY 1),
name varchar(255) NOT NULL,
company_id_FK INTEGER NOT NULL,
class_name varchar(255) NOT NULL,
--
PRIMARY KEY (employee_id),
FOREIGN KEY (company_id_FK) REFERENCES company (company_id)
);
CREATE TABLE manager_employee_map (
manager_id_FK INTEGER NOT NULL,
employee_id_FK INTEGER NOT NULL,
--
FOREIGN KEY (manager_id_FK) REFERENCES employee (employee_id),
FOREIGN KEY (employee_id_FK) REFERENCES employee (employee_id)
);
Repository mapping:
===============
<class-descriptor class="Company" table="COMPANY">
<field-descriptor name="id" column="COMPANY_ID"
jdbc-type="INTEGER"
primarykey="true" autoincrement="true" access="readonly"/>
<field-descriptor name="name" column="NAME" jdbc-type="VARCHAR" />
<collection-descriptor name="employees"
element-class-ref="Employee"
auto-delete="true" auto-update="true" auto-insert="true"
auto-retrieve="true">
<inverse-foreignkey field-ref="CompanyId"/>
</collection-descriptor>
</class-descriptor>
<class-descriptor class="Employee" table="employee">
<extent-class class-ref="Manager"/>
<field-descriptor name="id" column="EMPLOYEE_ID"
jdbc-type="INTEGER"
primarykey="true" autoincrement="true" access="readonly"/>
<field-descriptor name="name" column="NAME" jdbc-type="VARCHAR" />
<field-descriptor name="companyId" column="COMPANY_ID_FK"
jdbc-type="INTEGER"/>
<field-descriptor name="ojbConcreteClass" column="CLASS_NAME"
jdbc-type="VARCHAR" />
</class-descriptor>
<class-descriptor class="Manager" table="employee">
<field-descriptor name="id" column="EMPLOYEE_ID"
jdbc-type="INTEGER"
primarykey="true" autoincrement="true" access="readonly"/>
<field-descriptor name="name" column="NAME" jdbc-type="VARCHAR" />
<field-descriptor name="companyId" column="COMPANY_ID_FK"
jdbc-type="INTEGER"/>
<field-descriptor name="ojbConcreteClass" column="CLASS_NAME"
jdbc-type="VARCHAR" />
<collection-descriptor name="employees"
element-class-ref="Employee"
auto-retrieve="true" auto-update="true" auto-delete="true"
indirection-table="MANAGER_EMPLOYEE_MAP">
<fk-pointing-to-this-class column="MANAGER_ID_FK"/>
<fk-pointing-to-element-class column="EMPLOYEE_ID_FK"/>
</collection-descriptor>
</class-descriptor>
Adam Brons
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