Whether the el expression is null or not.

Whether the el expression is null or not.

$ {Empty object}. If it is null, true is returned; otherwise, false is returned;

$ {! Empty object.

Whether the el expression is null

Try this:
Logic: the empty label is used to determine whether it is null. If it is null, the content embedded in the label body will be processed. This label is used in the following scenarios:

When the Java object is null

When the String object is ""

When isEmpty () in the java. util. Collection object returns true

When isEmpty () in the java. util. Map object returns true

The following code demonstrates the logic: empty tag to determine whether the set persons is empty:

<Logic: empty name = "listForm" property = "persons">

<Div> the set persons is empty! </Div>

</Logic: empty>

Or <s: if test = "$ {workerCardBeanList}">
<Input type = "button" class = "buttonClass" name = "Save" $ {workerCardBeanList eq null? 'Disabled ': ''} value =" <s: text name = 'save'/> "onclick =" formSub (); "/>
</S: if>

How can I determine whether the c: if label is Null in the el expression?

Empty
It is used to judge an empty variable value: null, an empty String, an empty array, an empty Map, and a Collection with no entries
Directly use $ {empty member? "Null": "not null "}
The EL expression can be implemented in this way.