JPA JSF Assign value to a null object - jsf

Question

Good Afternoon in my timezone.
I am working on a web application, that uses both JSF and JPA.
There is one screen that contains multiple checkBoxes , something like this:
option1 check1 check2
option2 check1 check2
option3 check1 check2
In the database the query to retrieve the values of the checkboxes uses one LEFT JOIN (this is business logic) to retrieve the checkbox values:
Select * FROM Option LEFT OUTER JOIN CheckBoxType ....
The class diagram is something like this:
class Option
String label
checkBoxType checkBox
class CheckBoxType
boolean value;
The final result is , it could exist a list of "Option" in which some contains the checkBox variable to NULL.
In the JSF we use the following code:
<ui:repeat var="assocCheck" value="#{checkBean.getOptions}">
<h:selectBooleanCheckBox name="#{assocCheck.label}" value="#{assocCheck.checkBox.value}"/>
</ui:repeat>
To present the results there is no problem, in the case of the "Option" objects that contains the checkBox to null the checkbox on the screen appers with NO value , when i set to true one of this checkboxes and try to save them, the JSF throws a exception telling me the following
javax.faces.component.UpdateModelException: javax.el.PropertyNotFoundException: ....xhtml #45,126 value="#{assocCheck.checkBox.value}": Target Unreachable, 'null' returned null
I understand why this is happening , what is the best manner to deal with a problem like this ?Could adding a valueChangeListener on the checkbox(every time a checkbox is full filled there is a method on the bean that creates the checkBox object) be the best approach ?
Thanks in advance
Best regards

Answer 1

I would use a lazy setter / getter in your Option class:
#Entity
public class Option {
#...ToOne(optional = true, ...)
private CheckboxType checkbox;
public boolean isCheckboxChecked() {
return checkbox != null && checkbox.getValue();
}
public void setCheckboxChecked(boolean checked) {
if (checkbox == null) {
if (!checked) {
// No need to create a CheckboxType
return;
}
checkbox = new CheckboxType();
}
checkbox.setValue(checked);
}
}
Now you can use that one in your JSF page:
<h:selectBooleanCheckBox name="#{option.label}" value="#{option.checkBoxChecked}"/>
Why I would use this approach: It keeps the business logic attached to the business object. Especially the implicit statement checkbox == null means the same as checkbox.value == false is made explicit.
BTW: I would rename Checkbox.value to Checkbox.checked - from my point of view it makes things clearer: checkbox.isChecked() vs. checkbox.getValue() (or even worse checkbox.isValue()).