Simple setting from form input to object attribute - jsf

Question

<h:inputText value="#{myController.myString}" id="stg" />
<h:inputText value="#{myController.document.title}" id="title" />
<h:inputTextarea value="#{myController.document.subtitle}" id="subtitle" />
I can recover myString correctly, but document is always null. It has a default constructor. If I do a Document document = new Document() in myController then it is not null but title and subtitle are. Am I missing something?
EDIT
I thought my problem might not need additional information, but here it is:
.xhtml
<h:form id="ExampleForm" styleClass="myClass">
<h:inputText value="#{myController.myString}" id="stg" />
<h:inputText value="#{myController.document.title}" id="title" />
<h:inputTextarea value="#{myController.document.subtitle}" id="subtitle" />
<h:commandButton action="#{myController.readData()}" type="submit" value="Read"/>
</h:form>
Then I complete all the inputs in the form and click the button...
Controller
#Named(value = "myController")
#ViewScoped
public class MyController implements Serializable {
private String myString;
private Document document;
// getters and setters
public void readData() {
System.out.println("String: " + myString); // prints well
System.out.println("Doc: " + document); // prints null
// System.out.println("Doc title: " + document.getTitle()); // prints null when I declare private Document document = new Document();
}
}
Document is a Serializable simple bean with String title and subtitle and the respective getters/setters.
EDIT
The problem seems to be solved thanks to BalusC pointer.
There have been different things that mixed up and made my code work incorrectly. First, I solve the problem with:
#PostConstruct
public void init() {
document = new Document();
}
#PreDestroy
public void cleanup() {
document = null;
}
Another mistake I had while researching the issue (and that's why some other things created errors) was I didn't specify title and subtitle in the execute:
<h:commandButton action="#{myController.readData()}" type="submit" value="Read">
<f:ajax execute="#this title subtitle" />
</h:commandButton>