Thursday, September 13, 2012

Lazy-initializing beans in Spring: Exceptions


Lazy-initializing beans in a Spring container is generally desirable to allow for faster startup times, especially if there are lots of beans involved. However, there are some beans that must be loaded up or initialized when the application starts e.g. a background Quartz scheduler running jobs, or just doing 1st-level diagnostics or health check that writes results to a log file.

By default, all beans with scope="singleton" are initialized during container startup, but this behaviour can be changed by adding default-lazy-init="true" at the 'beans' top-level element, as shown (simplified for clarity):





To ensure a Spring-managed bean is initialized during container startup regardless of the attribute default-lazy-init="true" at the 'beans' top-level element in Spring configuration XML (or in Java code), you can one of the following:

  • Configure your bean definition to force initialization by adding attribute lazy-init="false", as shown in the example below:
    
    
  • Have your class implement the interface org.springframework.context.SmartLifecycle. This will guarantee the class will be initialized as long as isAutoStartup() is implemented to return 'true'. See the class Javadoc (http://static.springsource.org/spring/docs/3.0.x/javadoc-api/org/springframework/context/SmartLifecycle.html) for more info.


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