Do I have to put the code between <% and %> ?
That tells the engine that you're no longer using simple jAlbum scripting, and are, instead, writing Java/Groovy code. That's often simpler. For example:
<ja:if test="<%=level > 0%>">do something</ja:if>
Becomes:
<%
if(level > 0) {do something;}
%>
That frees you up to use more elaborate code, including more involved tests, like:
if(!someStringVariable.contains("mydog") {do something;}
This starts getting messy with jAlbum scripting.
It also makes nested
if/else if/else tests way easier.
If you look at the source code in one of my skins, you'll see jAlbum scripting in
index.htt and
slide.htt (it there is one), but virtually all of the
include files that are called from those templates live in the Java world.