Spring: Make sure a particular bean gets initialized first

Question

I have a library doing runtime setup and configuration of log4j (no log4j.properties or log4j.xml). I have defined a bean with class called MyLoggerFactory and I want this to be the first bean to be initialised using spring. I have seen that an issue has already been filed with spring to have support for order of initialisation but I was wondering whether there was a way to mark a bean as the first bean to be initialised by spring container?

Answer 1

Your options are:

1. Use @DependsOn annotation(available after spring 3.0.x) or depends-on xml-attribute and make all classes that use the configured loggers depend on the logger factory
2. Make the factory an actual factory for loggers, and inject the loggers into the beans instead of calling the factory directly – this is essentially the same as option 1, except the dependency is implied. This is the option I'd recommend.
3. Move the initialisation code to a part of your code where call order is specified – the main() method, or a ServletContextListener registered before the one that initializes Spring.

There is no way to explicitly define initialisation order in Spring and likely never will be – there's no way to define useful semantics for it considering you can load many application context configuration files which might have conflicting orderings. I've yet to see a case where the desired ordering couldn't be achieved by refactoring your code to better conform to the dependency injection pattern.