Calling Java function with arguments from StringTemplate?

There is a workaround by abusing dictionaries. Here is an example of implementing "function" for limiting item count in a List (issue on github).

In your code add dictionary:

group.defineDictionary("max", new MaxListItemsLimiter());

Usage (in this example first item in array is max. items count):

<max.(["50",myObject.items]):{msg|<msg.something>}>

final class MaxListItemsLimiter extends AbstractMap<String, Object> {

    @Override
    public Object get(Object key) {
        List items = (List) key;
        if (!items.isEmpty()) {
            //First item is max. count
            Integer limit = NumberUtils.toInt(items.get(0).toString(), -1); //use Integer.parseInt
            if (limit != -1) {
                return items.subList(1, Math.min(items.size(), limit + 1));
            } else {
                throw new AssertionError("First parameter in max must be number");
            }
        } else {
            return super.get(key);
        }
    }

    @Override
    public Set<Map.Entry<String, Object>> entrySet() {
        return Collections.emptySet();
    }

    @Override
    public boolean containsKey(Object key) {
        if (key instanceof List) {
            return true;
        } else {
            throw new AssertionError("You can use max only on Lists.");
        }
    }
}