How to use square bracket in EL JSF

Question

I have seen people using square bracket in JSF, and I am not sure if I understand its use correctly. So maybe an JSF guru can help me understand it

1.So let say I have this

#{bean.x}

and x is a two dimensional array (x[][]), how do I display x[0] using EL? I would imagine that I need to use square bracket in this case. I think I use #{bean.x[0]}, but I got exception.

2.The second scenario is from BalusC code Pass Argument to a composite-component action attribute

<composite:interface>
   <composite:attribute name="bean" type="java.lang.Object" />
   <composite:attribute name="action" type="java.lang.String" />
   <composite:attribute name="property" type="java.lang.String" />
</composite:interface>
<composite:implementation>
   <h:commandButton value="Remove" action="#{cc.attrs.bean[cc.attrs.action]}">
      <f:setPropertyActionListener target="#{cc.attrs.bean[cc.attrs.property]}" value="Somestring" />
   </h:commandButton>
</composite:implementation>

I understand what the code is doing and it works beautifully, but I would appreciate if someone can explain what is the use of the square bracket in this case. Thank you very much

Amylopectin

For the second part, cc.attrs is the map of parameters passed to the composition by the page. If bean has value myBean and action has value myAction, then #{cc.attrs.bean[cc.attrs.action]} would be the equivalent to #{myBean.myAction} (but passed as attributes to a composite, of course. – Breastwork

Answer 1

I think I use #{bean.x[0]}, but I got exception.

It's unfortunate that you didn't share the exception details. But this should just work, provided that there's a getX() method which returns a non-null array of which the given index really exists.

---

The second scenario is from BalusC code Pass Argument to a composite-component action attribute

In this particular case, the brace notation [] enables you to use a dynamic property name or action method name. The following of course don't work

#{cc.attrs.bean.cc.attrs.action}

It would only try to invoke bean.getCc().getAttrs().action().

The brace notation is also used on Map<K, V>. It allows you to specify keys which contain dots (which in turn shouldn't be EL-evaluated as properties)

#{bean.map['key.with.dots']}

It of course also allows you to specify a dynamic map key:

#{bean.map[otherBean.mapKey]}

See also:

• Our EL wiki page

Precatory

I think I use #{bean.x[0]}, but I got exception. This in fact does work. I wrote a small test case, and it works as expected. The exception was something else. Thank you for your insight – Amylopectin