Short way of making many beans depend-on one bean

Question

When using database migrations, I obviously want none of the DAOs to be usable before the migrations are run.

At the moment I'm declaring a lot of DAOs, all having a depends-on=databaseMigrator property. I find this troubling, especially since it's error prone.

Is there a more compact way of doing this?

---

Notes:

• the depends-on attribute is not 'inherited' from parent beans;
• I am not using Hibernate or JPA so I can't make the sessionFactory bean depend-on the migrator.

Answer 1

You could try writing a class that implements the BeanFactoryPostProcessor interface to automatically register the dependencies for you:

Warning: This class has not been compiled.

public class DatabaseMigratorDependencyResolver implements BeanFactoryPostProcessor {

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
        String[] beanNames = beanFactory.getBeanDefinitionNames();
        for (String beanName : beanNames) {
            BeanDefinition beanDefinition = beanFactory.getBeanDefinition(beanName);

            // Your job is here:
            // Feel free to make use of the methods available from the BeanDefinition class (http://static.springframework.org/spring/docs/2.5.x/api/org/springframework/beans/factory/config/BeanDefinition.html)
            boolean isDependentOnDatabaseMigrator = ...;

            if (isDependentOnDatabaseMigrator) {
                beanFactory.registerDependentBean("databaseMigrator", beanName);
            }
        }
    }

}

You could then include a bean of this class alongside all your other beans.

<bean class="DatabaseMigratorDependencyResolver"/>

Spring will automatically run it before it starts initiating the rest of the beans.