servlet-mapping's url-pattern selects the URLs to pass to Resin. servlet-mapping and url-pattern are part of the Servlet 2.3 standard, so there are many references explaining how it works.

url-pattern can take one of four forms:

• "/" matches all URLs. Use this to pass all requests to Resin.
• "/prefix/url/*" matches any URL starting with /prefix/url, including prefix/url itself. It does not match /prefix/urlfoo because any slash must immediately follow url
• "/exact/path" matches only the exact path. In other words, it will not match /exact/path/bogus.
• "*.ext" matches any URL with the extension ext. Resin allows path-infos, so /foo/bar.ext/path/info will also match.

If you want to use regular expressions in servlet-mapping, web-app, or hosts, you must use Apache-specific configuration to send the request to Resin. You can see this by looking at /caucho-status. /caucho-status will not display any regular expressions.

There are two special servlet-names which only affect the plugins: plugin_match and plugin_ignore.

plugin_match will direct a request to Resin. The servlet engine itself will ignore the plugin_match directive. You can use plugin_match to direct an entire subtree to Resin, e.g. to workaround the regexp limitation, but allow Resin's other servlet-mapping directives to control which servlets are used.

plugin_ignore keeps the request at on the web server. So you could create a directory /static where all documents, including JSPs are served by the web server.

web-apps collect servlets and JSP files into separate applications. All the servlet-mappings in a web-app apply only to the URL suffix.

In the following example, every URL starting with /prefix/url maps to the web-app. The servlet-mapping only applies to URLs matching the prefix.

In the exaple, mod_caucho will match any URL matching /prefix/url/*.foo. /prefix/url/bar.foo will match, but /test/bar.foo will not match.

host blocks configure virtual hosts. There's a bit of extra work for virtual hosts that we'll ignore here. (Basically, you need to add Apache ServerName directives so Resin knows the name of the virtual host.)

For dispatching, a host block gathers a set of web-apps. Each host will match a different set of URLs, depending on the web-app configuration. The default host matches any host not matched by a specific rule.

As usual, /caucho-status will show the URLs matched for each host.