How to save state when extending UIComponentBase

Question

I'm creating a composite component that will wrap a datatable to implement very simple paging. I need to save state (the current page number) between ajax requests.

I tried creating fields in my FacesComponent, but I discovered they are wiped out during the JSF lifecycle:

@FacesComponent(value = "bfTableComponent")
public class BFTableComponent extends UIComponentBase implements NamingContainer {

    private int currentPageNumber;
    ...

I can't seems to find a concise guide to doing this anywhere! How would one save state between requests when creating a composite component?

Answer 1

Use StateHelper . It's available by UIComponent#getStateHelper() .

private enum PropertyKeys {
    currentPageNumber;
}

public void setCurrentPageNumber(int currentPageNumber) {
    getStateHelper().put(PropertyKeys.currentPageNumber, currentPageNumber);
}

public int getCurrentPageNumber() {
    return (int) getStateHelper().eval(PropertyKeys.currentPageNumber, 0);
}

Note that I'm returning a default value of 0 in the getter. You might want to change int to Integer and remove the default value so that null will be returned.

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Unrelated to the concrete problem, you can for more simplicity also just extend UINamingContainer instead of implementing NamingContainer . This way you can omit the overridden getFamily() method as it's already implemented rightly by UINamingContainer .