Make JdbcOperationsSessionRepository.JdbcSession visible

[harbulot]

(This is using Spring Session 2.1.1.)

Please consider making JdbcOperationsSessionRepository.JdbcSession visible. Some use cases have already been suggested in #943 and #1217, here is another one.

I'm trying to implement a SpringSessionBackedSessionRegistry (mainly to implement getAllPrincipals()) backed by a JdbcOperationsSessionRepository, which itself implements FindByIndexNameSessionRepository<JdbcOperationsSessionRepository.JdbcSession>.

It would be good to be able to use the generic types:

public class JdbcSpringSessionBackedSessionRegistry extends
        SpringSessionBackedSessionRegistry<JdbcOperationsSessionRepository.JdbcSession> {
    
    public JdbcSpringSessionBackedSessionRegistry(
        JdbcOperationsSessionRepository sessionRepository) {
            super(sessionRepository);
	    // ...
    }
    // ...
}

However, JdbcSession is not visible, so this can't be used in a different package.

Here is a workaround, but we lose the generics checks:

@SuppressWarnings("rawtypes")
public class JdbcSpringSessionBackedSessionRegistry extends
        SpringSessionBackedSessionRegistry {

    @SuppressWarnings("unchecked")
    public JdbcSpringSessionBackedSessionRegistry(
        JdbcOperationsSessionRepository sessionRepository) {
            super(sessionRepository);
	    // ...
    }
    // ...
}

[vpavic]

As noted in the related issues we consider JdbcSession to be a JdbcOperationsSessionRepository implementation detail. With that in mind, you should really have your extension of SpringSessionBackedSessionRegistry parameterized with <S extends Session>.

Also could you clarify how this would help you implement SessionRegistry#getAllPrincipals since FindByIndexNameSessionRepository API doesn't expose an operation to retrieve all principals?

[vpavic]

Closing due to lack of feedback. Please comment back if you can provide more details and we can re-open the issue.

[harbulot]

@vpavic Apologies for the delay, I hadn't noticed the earlier comment.

As noted in the related issues we consider JdbcSession to be a JdbcOperationsSessionRepository implementation detail. With that in mind, you should really have your extension of SpringSessionBackedSessionRegistry parameterized with <S extends Session>.

It is indeed an implementation detail, but it's also effectively exposed as part of the generic signature of JdbcOperationsSessionRepository. It's hidden to a degree, but it's also a constraint that's not visible.

Even if the registry is parametrized, it won't be able to take JdbcOperationsSessionRepository as the parameter of the super constructor (SpringSessionBackedSessionRegistry(FindByIndexNameSessionRepository<S> sessionRepository)), because it's effectively not the same "S". JdbcOperationsSessionRepository is parametrised to use JdbcSession, which is then not visible.

Even with some parametrisation to the custom registry, this wouldn't work:

public class JdbcSpringSessionBackedSessionRegistry<S extends Session> extends SpringSessionBackedSessionRegistry<S> {
    public JdbcSpringSessionBackedSessionRegistry(JdbcOperationsSessionRepository sessionRepository) {
        super(sessionRepository); // THIS DOES NOT COMPILE.
	
        // ...
    }
}

Also could you clarify how this would help you implement SessionRegistry#getAllPrincipals since FindByIndexNameSessionRepository API doesn't expose an operation to retrieve all principals?

I can write the SQL queries directly in JdbcSpringSessionBackedSessionRegistry#getAllPrincipals(), precisely because I know that it's backed by JdbcOperationsSessionRepository.

[vpavic]

Sorry about late response to this @harbulot. If I understand correctly what you were trying to achieve, I'm not sure why simply something like this wouldn't work:

public class JdbcSpringSessionBackedSessionRegistry<S extends Session>
		extends SpringSessionBackedSessionRegistry<S> {

	private final JdbcOperations jdbcOperations;

	public JdbcSpringSessionBackedSessionRegistry(
			FindByIndexNameSessionRepository<S> sessionRepository,
			JdbcOperations jdbcOperations) {
		super(sessionRepository);
		this.jdbcOperations = jdbcOperations;
	}

	@Override
	public List<Object> getAllPrincipals() {
		// ...
	}

}

If you're deeper into customization, providing a custom SessionRepository implementation might be needed. We're not keen on opening up JdbcOperationsSessionRepository implementation details as that increases our API surface and makes it harder to evolve down the road.