Hello Paul, everyone,
One of the issues I was having with Jersey is a lack of reliable mechanism to cleanup any "closeable things" after request is done.
First let me clear up terminology - since Resource have a special meaning in JAX-RS I will call "closeable" what we typically call a resource in java (i.e. database connection, persistence manager, stream ....) - Anything which needs explicit closing after use.
One mechanizm which sems to work reliable is @PostConstruct and @PreDestroy but it is not very transparent and can not be used with injected "closeable" because injection happens implecetly while @PreDestroy must be declared explicetly so there is plenty of room for mistakes
Another approach is to cleanup in ContainerResponseFilter - have any injected or otherwise instantiated "closeable" register themselves in HttpContext.properties and have a ContainerResponseFilter to do clean up job.
Unfortunately it does not work because an exception in Resource method or in one of prior ContainerResponseFilter registered with Jersey will terminate filter chain leaving "cleaseable" unclosed.
It is not just that it does not work currently, I think it is not the best mechanism for cleanup job because exception handling logic of filter chain might be very well at odds with the need for gauranteed invocation of cleanup filters.
There is JDOResourceFilterFactory but it probably suffers the same issues and probably cannot take care of "closeables" fields in Resource since it will only be bound to methods if I understand correctly.
One very strong reason for needing cleanup stage is that when returning StreamingOutput response Resource method has no way to clean up after itself only container knows when to do cleanup! Without @PreDestroy entire use case of StreamingOutput is close to usless and @PreDestroy is pretty error prone. I can just see inexperienced developers either closing "closeable" inside Resource method and having StreamingOutput blow up on them or much worse - frustrated they just leave them open (what the hell) untill whole app runs out of database connections or whatever closeable they are using.
I realize that Jersey is not a general purpose IoC framework but it seems to me that ability to create or inject closeable with some guarantee of cleanup is just so core to any service that I do not see how it can be relegated to some other optional add-ons. To me it should be even defined in specs :)
I would greatly appreciate your feedback and suggestions
Thank you
Alex
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Alex Roytman
Peace Technology, Inc.
301-206-9696x103