The Spring container manages the bean initialization order. What if you have a bean that depends on another bean? You want to make sure that the dependent bean is initialized before the bean that needs it. @DependsOn helps you to achieve this when you configure beans using Java (not through XML).

You get the exception NoSuchBeanDefinitionException if a bean's initialization order is messed up and because of that the Spring container does not find the dependency.

Let's assume we have a bean named called BazBean that depends on the beans FooBean and BarBean. You can make use of the @DependsOn annotation to maintain the initializing order. The Spring container will follow the instructions and initialize both the FooBean and BarBean beans before creating BazBean.

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@Configuration

public class AppConfig {

    @Bean

    public FooBean fooBean() {

        return new FooBean();

    }

    @Bean

    public BarBean barBean () {

        return new BarBean ();

    }

    @Bean

    @DependsOn({"fooBean","barBean"})

    public BazBean bazBean (){

        return new BazBean ();

    }

}