I'm migrating a project to Spring Boot and I'm having some trouble with using the old database repositories. The old project was built as a WAR running on Tomcat, using persistence.xml with context.xml for the configuration of the database. The old repositories was accessed in a static way from various places which makes it really difficult to migrate them to Spring repositories. My problem is that it isn't possible right now to migrate the old repositories because all the services also need to be migrated etc.

One way I have tried is to initialize a LocalContainerEntityManagerFactoryBean then I can use application.yml for the DB configuration. I can also access this bean for the old classes and retrieve an EntityManagerFactory. Maybe it isn't the best approach. I have found some discussions about this.

public static <T extends Object> T getBean(Class<T> beanClass) {
    return context.getBean(beanClass);
}

...

LocalContainerEntityManagerFactoryBean localContainerEntityManagerFactoryBean =
            
SpringApplicationContext.getBean(LocalContainerEntityManagerFactoryBean.class);
EntityManagerFactory emf = localContainerEntityManagerFactoryBean.getObject();

This approach works if the application has started. My problem is I need to run some methods on startup which needs an EntityManagerFactory. I have tried to run

@PostConstruct
public void init() {

with no luck because the application context is null. So my question is how can I run my method after startup where I can access the application context? My application extends SpringBootServletInitializer for now so we can still deploy it as a WAR.