Why Does @Autowired Bean Return Null in Constructor?

Autowired Bean Initialization in Constructors

When attempting to reference an @Autowired bean from within the constructor of another bean, it may result in a null value. This phenomenon stems from the timing of the autowiring process.

Autowiring, a mechanism in Spring Framework, injects dependencies into beans based on their annotations. However, this injection occurs after the construction of the beans. Consequently, any attempt to access autowired beans within constructors will yield null values.

To mitigate this issue and initialize necessary dependencies, relocate the initialization code from the constructor to a separate method and annotate it with @PostConstruct. The Spring Framework guarantees that @PostConstruct methods are executed after bean construction and dependency injection.

For example, in the provided code, you could move the startOOServer() method outside the constructor and annotate it with @PostConstruct. This way, the autowired bean, applicationProperties, will be available before the method execution.

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