[Webmacro-devel] Why can't webmacro.jar be replaced without restart?

[Marc P. <ma...@an...>]

Guys, I imagine a few of use are familiar with this message after trying to 
replace webmacro.jar and restarting/reloading the web application without 
restarting the servlet container:

WebMacro Error:

Could not initialize the broker!
*** Check that WebMacro.properties was in your servlet
*** classpath, in a similar place to webmacro.jar *** and that all values 
were set correctly.
IO Error reading WebMacro.defaults
java.io.FileNotFoundException: JAR entry WebMacro.defaults not found in 
E:\Program Files\Apache Group\Tomcat 4.1\webapps\ignition\WEB- 
INF\lib\webmacro.jar
Please contact the server administrator


Do we know why this is happening? It is hard to see how it can be a WM 
thing, as it looks more like a generic classloader issue.

However I think this is a pretty serious problem we need to address, 
because it is really bad news if you have to ask a network admin to restart 
a shared Tomcat instance, thus bringing down everybody else's sites.

It looks like the problem is occurring here in Settings:

    public void load (String fileName) throws InitException, IOException
    {
        ClassLoader cl = this.getClass().getClassLoader();
        URL u = (cl == null) ? null : cl.getResource(fileName);
        if (u == null)
            u = ClassLoader.getSystemResource(fileName);
        if (u == null)
            try
            {
                u = new URL("file:" + fileName);
            }
            catch (MalformedURLException e)
            {
            }
        ;

	....
    }

Now, as the webapp is being reloaded by the container, everything should be 
running on top of a new ClassLoader and therefore this probably should work 
fine.

Perhaps there is some strange issue here with servlet containers (this is 
seen in Tomcat 4.1.18, 4.1.24 and I think Eric said Resin 2.x too) that we 
could work around by using ServletContext.getResource in Settings?

This would mean refactoring Settings to pass in the URL instead of the 
filename, which could be a good thing - putting the responsibility of 
finding the file on the caller (Broker).

Anybody think they might know what's going on here?

Marc
-- 
Marc Palmer
Contract Java Consultant/Developer
			
                        w a n g j a m m e r s

                 java and web software design
              experts with an ethical outlook

                   http://www.wangjammers.org