Selects requests by matching the URI against a regular expression.

The pattern is bound and matched against the path info of the servlet request, as this class assumes it is invoked by MetaServlet.

If there are capture groups in the regular expression, the matched ranges of the capture groups are stored as an array of modified HttpServetRequests, into the request attribute MetaFilter#REGEX_GROUPS. Using a capture group that may not capture, e.g. "(/foo)?", will cause an error at request handling time.

Each servlet request has been altered to have its getServletPath() method return the original path info up to the beginning of the corresponding capture group, and its getPathInfo() method return the matched text. A RegexGroupFilter can be applied in the pipeline to switch the current HttpServletRequest to reference a different capture group before running additional filters, or the final servlet.

Note that for getPathInfo() to start with a leading "/" as described in the servlet documentation, capture groups must actually capture the leading "/".

This class dispatches the remainder of the pipeline using the first capture group as the current request, making RegexGroupFilter required only to access capture groups beyond the first.