问题
I need to create a callback for <h:commandButton> while as a parameter I need to pass an argument that is string-concatenated with an external parameter id:
I tried nesting an EL expression something like this:
<h:commandButton ... action="#{someController.doSomething('#{id}SomeTableId')}" />
However this failed with an EL exception. What is a right syntax/approach to do this?
回答1:
If you're already on EL 3.0 (Java EE 7; WildFly, Tomcat 8, GlassFish 4, etc), then you could use the new += operator for this:
<h:commandButton ... action="#{someController.doSomething(id += 'SomeTableId')}" />
If you're however not on EL 3.0 yet, and the left hand is a genuine java.lang.String instance (and thus not e.g. java.lang.Long), then use EL 2.2 capability of invoking direct methods with arguments, which you then apply on String#concat():
<h:commandButton ... action="#{someController.doSomething(id.concat('SomeTableId'))}" />
Or if you're not on EL 2.2 yet, then use JSTL <c:set> to create a new EL variable with the concatenated values just inlined in value:
<c:set var="tableId" value="#{id}SomeTableId" />
<h:commandButton ... action="#{someController.doSomething(tableId)}" />
See also:
- String concatenation in EL for dynamic ResourceBundle key
来源：https://stackoverflow.com/questions/9680903/how-to-concatenate-strings-in-el-expression