Web Server: Custom URL Rewrite Rule Tutorial

If you want to take control of URL processing, you can create a custom Resin rewrite rule. Just like Resin's <resin:Forward> tag, your custom rule can match on a URL, and even have rewrite predicates like Resin's <resin:IfSecure> or <resin:IfHeader> or <resin:IfFileExists>.

A rewrite rule has two components:

• the action, which is a servlet javax.servlet.FilterChain
• the rule itself, which implements com.caucho.rewrite.DispatchRule

Once you write the action and the rule, you can use it in your WEB-INF/resin-web.xml just like any other rewrite rule.

In this example, we'll create a trivial rewrite rule that just displays the request URI and the target URI.

Using the rewrite rule in the resin-web.xml

To use your rule, you'll create an instance in the <web-app> using the standard CDI XML syntax.

WEB-INF/resin-web.xml

<web-app xmlns="http://caucho.com/ns/resin"
         xmlns:resin="urn:java:org.example.mypkg">

  <mypkg:MyDebugRewrite regexp="^/test/" target="/new/"/>

</web-app>

The FilterChain Action

qa/MyDebugFilterChain.java

package qa;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;

public class TestFilterChain implements FilterChain {
  private String _target;

  public TestFilterChain(String target)
  {
    _target = target;
  }

  public void doFilter(ServletRequest request,
                       ServletResponse response)
    throws ServletException, IOException
  {
    HttpServletRequest req = (HttpServletRequest) request;

    PrintWriter out = response.getWriter();

    out.println("URI: " + req.getRequestURI());
    out.println("target: " + _target);
  }
}

The Rewrite Rule

MyDebugRewrite.java

package qa;

import javax.servlet.*;
import javax.servlet.http.*;
import com.caucho.rewrite.*;

public class Test extends AbstractTargetDispatchRule
{
  @Override
  public FilterChain createDispatch(DispatcherType type,
                                    String uri,
                                    String queryString,
                                    String target,
                                    FilterChain next)
  {
    return new TestFilterChain(target);
  }
}