How to instantiate an entity with certain properties pre-set before use

[gozzie]

In a core JSF project, I used to initialize certain properties of an entity object with pre-defined values as early as its instantiation in a @PostConstruct method of a jsf managed bean (or even the managed bean's constructor). I can no longer preserve this functionality when porting the project to Seam with the managed bean gone.

Here's my code:

The entity class:

@Entity
@Name("task") // this line in Seam version
public class Task implements Serializable {

    private Integer id;
    private String subject;
    private Date creationDate;
    private Date completionDate;
    private Category category;
    private User user;

    public Task() {
    }

    public Task(Date creationDate) {
        this.creationDate = creationDate;
        this.user = user;
    }

    // getters & setters, etc.
}

The JSF Managed Bean

public class TaskBean extends BaseBean {

    // Super class provides the logged in user object and a default category object

    private Task task = new Task(java.util.Calendar.getInstance().getTime(), this.user);

    @PostConstruct
    public void initTaskBean() {
        if (certainConditionMet) 
            task.setCategory(defaultCategory);
    }

    // Other managed bean business...
}

The JSF page

<h:form>
<h:panelGrid columns="2">
    Date: <h:outputText value="#{taskBean.task.creationDate}">
            <f:convertDateTime pattern="dd/MM/yyyy" />
           </h:outputText>
    User:  <h:outputText value="#{taskBean.task.user.name}" />
    Subject: <h:inputText value="#{taskBean.task.subject}" id="subjectField" />
    Category: <h:selectOneMenu value="#{taskBean.task.category}" id="catMenu">
                <f:selectItems value="#{taskBean.categories}" />
              </h:selectOneMenu>
    // remaining stuff
</h:panelGrid>
</h:form>

The Stateless Session Bean in Seam version also assuming the responsibility of the jsf managed bean

@Name("taskAction")
@Stateless
public class TaskAction implements TaskActionLocal {

    @PersistenceContext
    private EntityManager em;

    @In private FacesMessages facesMessages;
    @In User user;
    @In Category defaultCategory
    @Logger private Log log;

    @In
    // private Task task = new Task(java.util.Calendar.getInstance().getTime(), user)
    // the above didn't work so 
    private Task task; 

    @PostConstruct
    public void baslarken() {
        System.out.println("TaskAction PostConstructed");
        task = new task(java.util.Calendar.getInstance().getTime(), user);
        if (certainConditionMet) 
                task.setCategory(defaultCategory);

        // the above won't work either. Date and User always blank on the ui form
    }

    // other business methods, etc
}

Seam version of the form:

<h:form id="todo" styleClass="edit">
    <rich:panel>
        <f:facet name="header">Task To Do</f:facet>

        <s:decorate id="dateField" template="layout/edit.xhtml">
            <ui:define name="label">Date:</ui:define>
            <h:outputText value="#{task.creationDate}"/>
        </s:decorate>

        <s:decorate id="userField" template="layout/edit.xhtml">
            <ui:define name="label">User:</ui:define>
            <h:outputText value="#{task.user.name}"/>
        </s:decorate>

        <s:decorate id="subjectField" template="layout/edit.xhtml">
            <ui:define name="label">Başlık</ui:define>
            <h:inputText id="subject" required="true" value="#{task.subject}" >
            <a4j:support event="onblur" reRender="subjectField" bypassupdates="true" ajaxSingle="true" />
            </h:inputText>
        </s:decorate>

        <!-- other components, etc -->
    </rich:panel>
</h:form>

I need advice on how to make the task object to hold the date and logged in user data (and preferably a default category) pre-populated when instantiated.

[vata2999]

define your task component instance in components.xml

<component name="user" class="User" />
<component class="Task" name="task">

<property name="creationDate">#{currentDate}</property>
<property name="user">#{user}</property>
</component>

instead of

 Task task = new Task(java.util.Calendar.getInstance().getTime(), this.user); 

use in your TaskBean

@In
Task task;

[serkan.s.eskici.online.nl]

There are many ways for doing this. I also prefer Omid's solution.

If you don't like XML and you want it done programmaticaly, then you could do it with for example with a @Factory.

@In(required=false)
Task task;


@Factory("task")
public Task newDefaultTask() {
   Task task = new Task();
   task.setProperty("default");
   //etc.
   return task;
}

public void save() {
   if(task.containsValueX())
      task.setProperty2("A");
  
   persist(task);
}

<h:inputText value="#{task.property}" />
...
<h:commandLink value="Save" action="#{taskBean.save}" />

Make sure that task is (at least) in a LRC scope if you want to inject it from another bean.

B.t.w. it's not a good practice to put @Name on an Entity bean.

[gozzie]

Omid and Serkan, thank you both so much for your respective advice.

Serkan, as far as what I know, @Factory annotated methods are invoked only once, therefore for it is OK to use it as long as the bean scope remains stateless or conversation, right? (Assume a case where the user is allowed to create consecutive tasks without leaving the page via AJAX in which case I could worry about that)

As for making entity beans Seam components via @Name, are you sure it's not OK? Examples shipped with Seam itself have such entities (@Entity + @Name). What's the inconvenience?

Final question: What does LRC stand for?

[serkan.s.eskici.online.nl]

Gökhan Ozar wrote on Oct 26, 2011 09:05:


Omid and Serkan, thank you both so much for your respective advice.

Serkan, as far as what I know, @Factory annotated methods are invoked only once, therefore for it is OK to use it as long as the bean scope remains stateless or conversation, right? (Assume a case where the user is allowed to create consecutive tasks without leaving the page via AJAX in which case I could worry about that)

Yes this is correct. @Factory just initialises a component and sets it in a (map of certain) scope. If you call the factory again and the scoped component still exists, then the @Factory method won't be called again, but just read from memory/scope.

As for making entity beans Seam components via @Name, are you sure it's not OK? Examples shipped with Seam itself have such entities Entity + Name. What's the inconvenience?

The examples are outdated. There is actually no need to set @Name on an entity if you follow the examples above.
The most important reason for me to not use @Name on entities is because an entity can have different roles e.q. different names. For example you can have a 'task' and a 'defaultTask'.
Seam has @Roles annotations for that, but it seems that there are performance problems with it, so I don't use it.

And another important reason for not using @Name is that you keep your entities clean from Seam dependencies.

Final question: What does LRC stand for?

Long running conversation.