Prevent Managed Bean From Being Instantiated Multiple Times

Question

I'm new to Java so sorry if my terminology is not correct.

I have a managed bean setup (PolicyInformation) with a session scope that I instantiate in my Java code with:

thisPolicy = (PolicyInformation) Utils.getSessionMapValue("policyInformationBean");
if (thisPolicy == null) {
    thisPolicy = new PolicyInformation();
}

The code above checks if the bean already exists, and if it does, it uses the object in the session map. It seems to work great.

However, if I add a label on my XPage to display a value from my PolicyInformation managed bean with the following code (using expression language):

<xp:label value="#{policyInformationBean.name}"/>

the managed bean runs twice: once when I call it in my Java class, and again when I add the label above.

Is there a way I can prevent that second call when adding the label on my XPage? Can I somehow get the value from the Java session map in my XPage label?

faces-config:

<managed-bean>
<managed-bean-name>policyInformationBean</managed-bean-name>
<managed-bean-scope>session</managed-bean-scope>
<managed-bean-class>com.package.PolicyInformation</managed-bean-class>
</managed-bean>

Please also show your faces-config XML file. With a managed bean you shouldn't ever have to use the 'new' keyword. — Steve Zavocki
Now if you want to control the creation of your bean, which is very common and useful, then your bean would be a POJO. The term managed bean implies that the creation is done for you. — Steve Zavocki
also, look at JSF lifecycle (methods can be called multiple times) and bear in mind it is hard to make singleton in XPages (because of multiple class loaders) — Frantisek Kossuth
Do you add your manually created bean to the session scope after instantiating it? — Sven Hasselbach

Steve Zavocki Steve Zavocki · Accepted Answer · 2015-04-09T21:00:13

Please consider these three things:

Try adding an "id" property to your managed bean opening tag with the same name as your managed-bean-name. This is likely not your problem, but this is how we set it up.

Example:

<managed-bean id="dBar">
<managed-bean-name>dBar</managed-bean-name>
<managed-bean-class>eu.linqed.debugtoolbar.DebugToolbar</managed-bean-class>
<managed-bean-scope>session</managed-bean-scope> 
</managed-bean>

Remove all code that creates a new PolicyInformation object. To be managed, you have to let the framework manager it all the time. I think you might be confusing it, by creating another object.
Alternatively, you could make this bean a POJO (Plain Old Java Object) and not a managed bean at all. This way you just create the object when you need it. You would not have an entry in faces-config anymore, and you would use the 'new' keyword when you need to create it. When the reference becomes null, then garbage collection will clean it up.

Prevent Managed Bean From Being Instantiated Multiple Times

2 Answers