What is the Spring DI equivalent of Dagger2 Subcomponents

Question

Dagger2 has Subcomponents https://medium.com/tompee/dagger-2-scopes-and-subcomponents-d54d58511781 for using DI with shorter lifecycles than the main application, for example if you have a job service then the service will have a Component with Subcomponents for each job.

What is the equivalent for Spring's DI framework?

Answer 1

The only possibility I can see is to use context hierarchy and to handle context with shorter lifecycle manually.

// Does Dagger's @Subcomponent.Factory work
public class JobExecutor {
    private final ApplicationContext mainApplicationContext;

    @Inject
    public JobExecutor(ApplicationContext mainApplicationContext) {
        this.mainApplicationContext = mainApplicationContext;
    }

    public Result execute(Job job) {
        AnnotationConfigApplicationContext jobContext = null;
        try {
            jobContext = new AnnotationConfigApplicationContext();
            jobContext.setParent(mainApplicationContext); // Provides access to common beans
            jobContext.register(SpringJobContext.class);
            jobContext.getBeanFactory().registerSingleton("job", job); // Does Dagger's @BindsInstance work
            jobContext.refresh();
            // You can access and execute one of the beans from jobContext manually or use @PostConstruct
            return jobContext.getBean(JobExecutorFromJobContext.class)
                    .execute();
        } finally {
            if (jobContext != null) {
                jobContext.destroy();
            }
        }
    }

    static class JobExecutorFromJobContext {
        private final Database database; // From parent's context
        private final Job job;

        @Inject
        JobExecutorFromJobContext(Database database, Job job) {
            this.database = database;
            this.job = job;
        }

        public void execute() {
            // ...
        }
    }
}