javadependency-injectionjakarta-eecdijsr299

Why use @PostConstruct?


In a managed bean, @PostConstruct is called after the regular Java object constructor.

Why would I use @PostConstruct to initialize by bean, instead of the regular constructor itself?


Solution

    • because when the constructor is called, the bean is not yet initialized - i.e. no dependencies are injected. In the @PostConstruct method the bean is fully initialized and you can use the dependencies.

    • because this is the contract that guarantees that this method will be invoked only once in the bean lifecycle. It may happen (though unlikely) that a bean is instantiated multiple times by the container in its internal working, but it guarantees that @PostConstruct will be invoked only once.