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A common question Mule ESB users have is: How do I perform some actions on Mule startup? Well, the fact is one can do it many ways, including:

  • Programmatically get a hold of MuleContext in your component or agent (e.g., by implementing MuleContextAware) and register your listener and interest in a specific event. Typically the MuleContextNotification.CONTEXT_STARTED is the one you’d want.
  • A combination of a listener and declarative registration. For an example, see this forum post for a solution.

Today, however, I want to talk about yet another option, which often goes unnoticed. In fact it is one of my favorites, as it provides for conventions-over-configuration approach: bootstrapping the registry. The documentation has more details, but here’s how one would do it:

  1. Create your class (it needs not even be any Mule agent or component, can just be your own POJO) and package it as a JAR.
  2. Add the file in the JAR at META-INF/services/org/mule/config/ with the following entry:
  3. Drop the JAR in $MULE_HOME/lib/user and enjoy!

Your class will then be added to Mule’s internal registry and put through a complete lifecycle if needed (see the documentation link above). As long as the JAR is available to Mule, the class will be started automatically, without any extra configuration steps.