How to concatenate string and url attribute value in Xpath?

Question

Parsing

Using Xpath, I want to concatenate this string: "/images/products/"
and the url attribute values ​​in the following code snippet:

<div id="small-images">
    <ul>
       <li url="1.jpeg"></li>
       <li url="2.jpeg"></li>
       <li url="3.jpeg"></li>
    </ul>
    </div>

I would like to get this result:
/images/products/1.jpeg
/images/products/2.jpeg
/images/products/3.jpeg
Tried to do this:
concat(//div[@id="small-images"] /li/@url, '/images/products/')
and so:
string-join(//div[@id="small-images"]/li/@url, "/images/products/")
Doesn't work .
How to concatenate string and result url attribute in Xpath?
Update: In general, as I understand this problem, there is no solution without writing additional plugins and dancing with a tambourine

Answer 1

What do you mean it doesn't work? Have you looked at what your selector returns? Is it really the right URL value?
You need either this
or that
There is no element you are looking for, because you are looking for li in immediate descendants (and there is also ul first)