Lifecycle

Clawject allows us to attach custom actions to bean or application creation and destruction, and it is done using the @PostConstruct and @PreDestroy decorators.

@PostConstruct and @PreDestroy can be used in @Configuration, @ClawjectApplication classes and in Beans. You can decorate method or property with arrow function, also decoration target should not be static.

@PostConstruct and @PreDestroy can be used together at the same method — so the method will be called twice.

Note that @PostConstruct and @PreDestroy works a little different in configuration classes and in Beans, when using in configuration classes - you can pass arguments to the method, these arguments will be treated as a dependencies, and container will inject appropriate Beans to the method, in other hand, when using in Bean - you can't pass arguments to the method, container will not inject anything to the method and will report compilation error.

@PostConstruct

Clawject calls the methods annotated with @PostConstruct only once, just after the initialization of bean or application.

@PostConstruct in Context

Let's use the @PostConstruct decorator in the @Configuration class:

@ClawjectApplication
class Application {
  @Bean foo = 'string';

  @PostConstruct
  postConstruct(stringBean: string) { // <- "foo" bean will be injected here
    console.log(`MyContext has been created, "stringBean" value is ${stringBean}`);
  }
}

@PostConstruct in Bean

Let's use the @PostConstruct decorator in the Bean:

class Foo {
  @PostConstruct
  postConstruct() {
    console.log('Foo bean has been created');
  }
}

Now when we register this class as a Bean in context - the postConstruct method will be called when Foo instance is created.

@PreDestroy

Clawject calls the methods annotated with @PostConstruct only once, just before context clearing or bean removal from context.

The purpose of this method should be to release resources or perform other cleanup tasks, such as closing a database connection, before the bean gets destroyed.

@PreDestroy in Context

Let's use the @PreDestroy decorator in the Context:

@ClawjectApplication
class Application {
  @Bean foo = 'string';

  @PreDestroy
  preDestroy(stringBean: string) { // <- "foo" bean will be injected here
    console.log(`MyContext is going to be destroyed, "stringBean" value is ${stringBean}`);
  }
}

@PreDestroy in Bean

Let's use the @PreDestroy decorator in the Bean:

class Foo {
  @PreDestroy
  preDestroy() {
    console.log('Foo bean is going to be destroyed');
  }
}

Now when we register this class as a Bean in context - the preDestroy method will be called when Foo bean is going to be destroyed.