My favorite "use spring to instantiate but register as a static global singleton" solution

ActivityStateManagerImpl.java

@Service("blActivityStateManager")
public class ActivityStateManagerImpl implements ActivityStateManager {

    private static ActivityStateManager ACTIVITY_STATE_MANAGER;

    public static ActivityStateManager getStateManager() {
        return ACTIVITY_STATE_MANAGER;
    }

    @PostConstruct
    public void init() {
        ACTIVITY_STATE_MANAGER = this;
    }
    
    ....
}