There seems to be an issue with URL parameters encoded into path in form "/page/param1/val1" with handling parameter values with forward slash ('/'). The slash is correctly URL-encoded to entity '%2F' so that for example parameter key/value pair 'foo' => 'b/a/r' is encoded into url like: '/page/foo/b%2Fa%2Fr'. The problem is that Tomcat returns error or empty page with this url.
I tested and researched a little bit and found out that this is Tomcat related issue. In versions >= 6.0.10 Tomcat does not allow entities '%2F' and '%5C in path by default so it responds with error (or empty page) when it encounters one of them in URL's path part. More information can be found on http://tomcat.apache.org/security-6.html, under header "Fixed in Apache Tomcat 6.0.10". I tried according to the document to turn system property org.apache.tomcat.util.buf.UDecoder.ALLOW_ENCODED_SLASH to true, to allow encoded slashes in path, and got the request with '%2F' in path through.
I think that PageParameters in wicket should be easy to use, so that user does not have to worry about the contents of the parameter, so something should be done to this issue.
I managed to get around this issue by double encoding the parameter values with URLEncoder. I encoded the PageParameter map parameter values with URLEncoder and replaced all occurences of '%' in resulting text with '=' before passing it forward. So only entity that is left to be encoded by the framework (AbstractRequestTargetUrlCodingStrategy) is '=' which becomes "%3D" so "foo" => "b/a/r" becomes encoded in URL like: "/page/foo/b%3D2Fa%3D2Fr". Decoding of URL is done by opposite operation sequence: framework decodes the parameter for me to form b=2Fa=2Fr and after that I replace '=' with '%' and the replaced string is further decoded with URLDecoder. Not very beautiful solution but seems to work as a quick fix and leaves non-special characters unaffected. As a little downside two extra characters are needed to encode every special character.