Question

I have a filter that is currently defined to run after the view is rendered:

class MyFilter {
  def filters = {
    doStuff(controller: '*', action: '*') {
      before = {...}
      after = {...} 
      afterView = { 
        // code I want to run when EVERYTHING is set and done }
        Holder.setCurrentData(null)
    }
  }
}

This should work, but I noticed that <g:message /> tags (and possibly others; this is the one what interests me at this point) are executed after the afterView filter.

This is a problem because I use this filter to keep track of some information for the current execution in a ThreadLocal, and I want to make sure I clean up after myself when the request is done. I don’t want to use the request/session object to shuffle the data along, because then I have to pass it to all the calls I make; as it is, I have a Holder class that I can query for the value in the ThreadLocal.

I need the information from that ThreadLocal in my custom MessageSource. That’s how I noticed that <g:message /> is called after the afterView filter.

Answer 1

You can use a servlet filter:

package com.mycompany

import java.io.IOException;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

import org.springframework.web.filter.GenericFilterBean;

public class MyFilter extends GenericFilterBean {

   public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
            throws IOException, ServletException {

      try {
         chain.doFilter(req, res);
      }
      finally {
         Holder.setCurrentData(null);   
      }
   }
}

Run grails install-templates if you haven’t already and then you can register it in src/templates/war/web.xml like this:

<filter>
   <filter-name>myFilter</filter-name>
   <filter-class>com.mycompany.MyFilter</filter-class>
</filter>

<filter-mapping>
   <filter-name>myFilter</filter-name>
   <url-pattern>/*</url-pattern>
</filter-mapping>

I’ve extended GenericFilterBean for convenience but you could also just implement the javax.servlet.Filter interface directly. It could also be written in Groovy, but I tend to write filters in Java since they’re called for every request, and the small overhead that Groovy adds can add up here.