Nicolas Richeton

When developping Java web apps, you may sometime see random startup errors like this one :

java.lang.IllegalStateException: Unable to instantiate container.
at org.apache.tiles.web.startup.TilesListener.contextInitialized(TilesListener.java:60)
at org.mortbay.jetty.handler.ContextHandler.startContext(ContextHandler.java:549)
at org.mortbay.jetty.servlet.Context.startContext(Context.java:136)
at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1282)
at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:518)
at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:499)
(...)


Most of the time your application works, but sometimes it just does not start.

This is because of the dtd resolution mecanism: if you use the reference of a dtd which is not in the webapp classpath, the container will try to get it from internet.

If the remote site is down (in this case http://tiles.apache.org), your app will no longer start.

Sadly, it’s easy to get in this situation.

• Upgrade a library without updating xml headers
• Copy/Paste a snippet from the elsewhere

… and the container will start to fetch dtds from the internet.

In my case, the previous error was caused by :

<?xml version="1.0" encoding="ISO-8859-1" ?>

<!DOCTYPE tiles-definitions PUBLIC
"-//Apache Software Foundation//DTD Tiles Configuration 2.1//EN"
"http://tiles.apache.org/dtds/tiles-config_2_1.dtd">

<tiles-definitions>
(...)
</tiles-definitions>

instead of :

<?xml version="1.0" encoding="ISO-8859-1" ?>

<!DOCTYPE tiles-definitions PUBLIC
"-//Apache Software Foundation//DTD Tiles Configuration 2.0//EN"
"http://tiles.apache.org/dtds/tiles-config_2_0.dtd">

<tiles-definitions>
(...)
</tiles-definitions>

With tiles 2.0.6 in the classpath.

Conclusion
Be sure to use the exact version of the dtd in your classpath. Don’t pickup examples from the internet without double-checking the dtd.
This will prevent longer startup times and potential random errors.

Note: this post dedicated to Olivier and Jimmy