How do you get the length of a list in the JSF expression language?

Question

How would I get the length of an ArrayList using a JSF EL expression?

#{MyBean.somelist.length}

does not work.

Answer 1

Note: This solution is better for older versions of JSTL. For versions greater then 1.1 I recommend using fn:length(MyBean.somelist) as suggested by Bill James.

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This article has some more detailed information, including another possible solution;

The problem is that we are trying to invoke the list's size method (which is a valid LinkedList method), but it's not a JavaBeans-compliant getter method, so the expression list.size-1 cannot be evaluated.

There are two ways to address this dilemma. First, you can use the RT Core library, like this:

Second, if you want to avoid Java code in your JSP pages, you can implement a simple wrapper class that contains a list and provides access to the list's size property with a JavaBeans-compliant getter method. That bean is listed in Listing 2.25.

The problem with c_rt method is that you need to get the variable from request manually, because it doesn't recognize it otherwise. At this point you are putting in a lot of code for what should be built in functionality. This is a GIANT flaw in the EL.

I ended up using the "wrapper" method, here is the class for it;

public class CollectionWrapper {

    Collection collection;

    public CollectionWrapper(Collection collection) {
        this.collection = collection;
    }

    public Collection getCollection() {
        return collection;
    }

    public int getSize() {
        return collection.size();
    }
}

A third option that no one has mentioned yet is to put your list size into the model (assuming you are using MVC) as a separate attribute. So in your model you would have "someList" and then "someListSize". That may be simplest way to solve this issue.