Avoiding the DRY Principle with beans
Question, I find myself doing something wrong with seam beans....and that is copying and pasting ad nauseum and violating the DRY Priniciple (Don't Repeat Yourself). Here is a prime example
package com.evolutionnext.session;
import com.evolutionnext.data.Employee;
import java.io.Serializable;
import javax.ejb.Stateful;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.PersistenceContextType;
import org.hibernate.validator.Valid;
import org.jboss.seam.ScopeType;
import org.jboss.seam.annotations.In;
import org.jboss.seam.annotations.Name;
import org.jboss.seam.annotations.Scope;
@Stateful
@Scope(value=ScopeType.SESSION)
@Name(value="employeeBean")
public class EmployeeBean implements Serializable, EmployeeLocal {
@PersistenceContext(unitName="hrsystem",
type=PersistenceContextType.EXTENDED)
private EntityManager entityManager;
@In @Valid
private Employee employee;
/** Creates a new instance of EmployeeBean */
public EmployeeBean() {
}
public void setEmployee(Employee employee) {
this.employee = employee;
}
@In @Valid
public Employee getEmployee() {
return employee;
}
public String update() {
entityManager.merge(employee);
return "Success";
}
public String create() {
entityManager.persist(employee);
return "Success";
}
public String delete() {
entityManager.remove(employee);
return "Success";
}
}
All is well with this code...now what happens if I want the same functionality for uh...department, well I would need to copy and paste this code. This would violate the dry principal and make my app fragile in the process.
One solution I thought would be to create a superclass and refactor my create, update, and delete methods. This is almost an elegant solution but still has some copy/pasting problems. Here is the code...
package com.evolutionnext.session;
import java.io.Serializable;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.PersistenceContextType;
public abstract class PersistentBean implements Serializable, PersistentLocal {
@PersistenceContext(unitName="hrsystem",
type=PersistenceContextType.EXTENDED)
private EntityManager entityManager;
private Object object;
public abstract void setObject(Object object);
public abstract Object getObject();
public String update() {
entityManager.merge(object);
return "Success";
}
public String create() {
entityManager.persist(object);
return "Success";
}
public String delete() {
entityManager.remove(object);
return "Success";
}
}
My EmployeeBean would like this now:
package com.evolutionnext.session;
import javax.ejb.Stateful;
import org.jboss.seam.ScopeType;
import org.jboss.seam.annotations.In;
import org.jboss.seam.annotations.Name;
import org.jboss.seam.annotations.Out;
import org.jboss.seam.annotations.Scope;
/**
*
* @author Administrator
*/
@Stateful
@Scope(value=ScopeType.SESSION)
@Name(value="employeeBean")
public class EmployeeBean extends PersistentBean {
/** Creates a new instance of EmployeeBean */
public EmployeeBean() {
}
private Object object;
public void setObject(Object object) {
this.object = object;
}
@In(value="employee") @Out(value="employee")
public Object getObject() {
return object;
}
}
I am not even sure if this type of subclassing works in Seam. Is this what I have to look to as far as abstraction. Let me know. ;)
