Actually, for me there is something above. My use case is unusual. Our customers often belong to large organizations that have autocratic IT departments. The customer buys and is responsible for our app, but IT owns and controls access to the hardware. Simple things like editing config files, viewing logs, and restarting the app become difficult. The customer must schedule time with IT, and only IT can make the changes.
Accordingly, I'm trying for "IT-free" installation, configuration, and maintenance. All IT does is set up the box, install the app server and database, and drop in our war file. The customer completes the installation and does all subsequent configuration and maintenance *through the app*. This means the app must be able to start without a working database connection, allow the customer to specify that connection, and then switch to using the new connection, all without a restart (which would require IT). The app must also be able to fall back to a minimal "safe mode" if the database connection later fails, such as when IT changes the database password, which some do monthly. Amazingly, I've found a way to actually do this. I wrapped TapestryFilter in a filter of my own (I suppose the GoF would call it a decorator). My filter's init method inits TapestryFilter, which, of course, brings up the IOC registry. I have a service which uses Hibernate during its initialization, so if Hibernate can't talk to the database, it dies. The exception propagates up through the IOC registry and TapestryFilter to my filter, which discards the TapestryFilter instance (and thus the IOC registry), adjusts the Hibernate settings to safe mode (i.e. hsqldb), and creates a new TapestryFilter. The app can then allow login via a special admin account (which is defined in a file so it works without a database). The admin fixes the database parameters, and my filter discards the safe-mode TapestryFilter and creates yet another new TapestryFilter using the new parameters. If that fails, back to safe mode and try again. This all works hunky dory, provided that when Hibernate fails I get the exception. Usually I do, but if the failure happens during the ending commit, ThreadCleanupHubImpl.cleanup swallows it, per my original message, and my filter has no way of knowing that something went wrong. I understand your point, though, that all services must be allowed to finish their cleanups. Perhaps ThreadCleanupHubImpl could save any exception and re-throw it after it's done. As a last add-on to an already overlong note, I wonder if there's a more elegant way of achieving my goal. Perhaps there's some way of discarding and recreating only those services that depend, directly or indirectly, on Hibernate, rather than tossing the entire IOC registry and TapestryFilter. I do get an error message when I do this, as somebody (I forget who) retains a weak static reference to part of the IOC registry and complains at what appears to be my attempt at creating two registries. ----- Original Message ---- From: Howard Lewis Ship <[EMAIL PROTECTED]> To: Tapestry users <users@tapestry.apache.org> Sent: Sunday, January 20, 2008 9:01:07 AM Subject: Re: T5.0.7: ThreadCleanupHubImpl.cleanup swallows exceptions By the time it executes, it is too late to render a response with the exception. There's nothing that can catch the exception ... the only thing "above" ThreadCleanupHubImpl is the servlet and then the servlet container. Further, it is very important that every cleanup listener be invoked, or you could experience some memory leaks in the application, as threads hold onto objects inside ThreadLocals. On Jan 11, 2008 2:33 PM, Franz Amador <[EMAIL PROTECTED]> wrote: > ThreadCleanupHubImpl.cleanup (line 53) catches exceptions thrown by service initialization cleanup. It logs them, which is good, but it doesn't pass them up, which is causing me problems. I want to know if Hibernate initialized successfully, but this prevents me from seeing exceptions thrown during the transaction commit in HibernateSessionManagerImpl.threadDidCleanup. Is this an oversight or is there a design goal of having the Registry come up no matter what? > > -- Howard M. Lewis Ship Creator Apache Tapestry and Apache HiveMind --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
