[jboss-user] [JBoss Seam] - 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. ;)
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