How to call parameterized method from JSP using JSTL/EL

Question

You can only invoke methods with arguments in EL if you’re targeting and running at least a Servlet 3.0 compatible container (e.g. Tomcat 7 or newer, WildFly 8 or newer, GlassFish 3 or newer, etc) with a web.xml declared conform at least Servlet 3.0. This servlet version comes along with EL 2.2 which allows invoking arbitrary instance methods with arguments.

Assuming that you’ve a ${bean} in the scope which refers to an instance of a class which has a method something like public Object[] getArray(String key), then you should be able to do this:

<c:forEach items="${bean.getArray('foo')}" var="item">
    ${item} <br />
</c:forEach>

or even with another variable as argument

<c:forEach items="${bean.getArray(foo)}" var="item">
    ${item} <br />
</c:forEach>

But if you don’t target a Servlet 3.0 container, then you cannot invoke methods with arguments in EL at all. Your best bet is to just do the job in the preprocessing servlet as suggested by Duffymo.

Object[] array = bean.getArray("foo");
request.setAttribute("array", array);
// ...

As a completely different alternative, you could create an EL function which delegates the method call. You can find a kickoff example as option 2 of this answer How to call a static method in JSP/EL? You’d like to end up something like as:

<c:forEach items="${util:getArray(bean, 'foo')}" var="item">
    ${item} <br />
</c:forEach>

with

public static Object[] getArray(Bean bean, String key) {
    return bean.getArray(key);
}

The web.xml file should absolutely not have a <!DOCTYPE> line in top as that would otherwise still force the Servlet 2.3 modus. You can find examples of proper web.xml declarations in the second half of this answer How to install JSTL? The absolute uri: http://java.sun.com/jstl/core cannot be resolved.

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