Parameterized component parameter returns IllegalArgumentException if no value is set in a sitemap item

In the component config
hst:parametername pagetype
hst:parametervalue ${pagetype}

In the sitemap matcher: no hst:parametername/hst:parametervalue

In the component class:
String pagetype = getParameter("pagetype", request);

getParameter gets an IllegalArgumentException because the underlying classes get ${pagetype} instead of null.

If you remove the hst:parametername/hst:parametervalue pair from the component config String pagetype is null (which is good).

Sometimes you want to set the configuration parameter in the component but if no value is passed from the sitemap, you can use some default value (which may be hardcoded in your component class).