Is it safe to pass EL-Bound component as action listener parameter in JSF?

Question

If I upgrade from Mojarra 2.1.21 to Mojarra 2.1.22, 23, 24, or 26, I became an error in my view. The error has something to do with binding. (Duplicate component id) because I had binding to sessionScoped bean properties. I have changed my bean to use EL-scoped binding. So my question:

Is it safe to use EL-Binding and give a bound component as parameter and read(and set properties on this component). E.g.

View:

 <p:dataTable binding="#{table}"> ...</p:dataTable>
 <p:commandButton action="#{bean.doit(table)}" />

Bean:

 public void doit(DataTable dt) {
    dt.getSomething();
    dt.setSomething();
 }

Why it's first happened from Mojara version 2.1.22 (this version number included) ?

score 2 · Accepted Answer · edited May 23 '17 at 12:03

Is it safe to use EL-Binding and give a bound component as parameter and read(and set properties on this component). E.g.

Point is, you should never bind a component as a property of a bean which is in broader scope than the request scope. UI components are inherently request scoped. During building/restoring of the view, JSF will check if the getter doesn't already return an existing component and then reuse it instead of creating a new one the usual way. However, if the bean returns an already-created one from a previous/other request/view/session which belongs to a completely different view, then this all would fail as the state collides.

In this particular solution, you're nowhere referencing the component as a bean property, so that's absolutely safe. But, probably better yet is to just bind the particular component attribute you're actually interested in instead of the whole component:

<p:dataTable something="#{bean.something}">

with

private String something;

public void doit() {
    System.out.println(something);
    something = "something new";
}

Is it safe to pass EL-Bound component as action listener parameter in JSF?

1 Answers1

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