Is it possible to use JSP sort of as a template without having code inside?
Values should be inserted into a hash map, and the JSP can read the values from there.
Is it possible to code like this in a GAE application, or do you need external tools/frameworks to accomplish this?
In other words, is it possible to pass values from the servlet handler to the JSP template?
Next to JSP there's also the Servlet API.
If the map is request or session specific, then create a class which extends HttpServlet and implement doGet() method like follows:
Map<K, V> map = createItSomehow();
request.setAttribute("map", map);
request.getRequestDispatcher("/WEB-INF/page.jsp").forward(request, response);
Register the Servlet in web.xml on a certain url-pattern and invoke an URL matching this pattern.
This way the map is available as ${map} in JSP. Here's an example which iterates over the map using JSTL c:forEach tag:
<c:forEach items="${map}" var="entry">
Key: ${entry.key}, Value: ${entry.value}<br>
</c:forEach>
If the map is an application wide constant, then rather implement ServletContextListener and do the following in contextInitialized() method:
Map<K, V> map = createItSomehow();
event.getServletContext().setAttribute("map", map);
Register the ServletContextListener in web.xml as follows:
<listener>
<listener-class>com.example.Config</listener-class>
</listener>
and it will be executed on webapp's startup. The map is then available in JSP by ${map} as well.