Hi Adrian, and thanks for replying. I understand your point, but the subtlety is that a transactional connection is per function invocation where as the database component is per Component lifecycle - passing the db around isn't sufficient here.
Spring plumbing binds a transactional connection to a thread local and then passes a connection proxy around - accessing that proxy magically (through the use of the lovely AOP) resolves to the current thread-local transactional connection. I don't see any option other than to re-implement that in Clojure or pass an explicit 'unit-of-work' around but it all feels wrong in Clojure. The problem at the moment is that the implementation of each protocol will execute in separate transactions. On 4 March 2015 at 18:06, <adrian.med...@mail.yu.edu> wrote: > Having never used Spring (or anything else resembling the style of code you > presented) I don't really know if I'm understanding what you're asking. > > However, it might be useful to wrap your database in a component. I do this > for Datomic all of the time, and the boilerplate looks something like this: > https://gist.github.com/aamedina/a1ca5e97c1a5d73fe141. I'm not sure exactly > how this would fit into JDBC, but I'm sure you can figure it out if you > think it would be worthwhile. > > I then pass the database component to any other component in my system that > I know will make use of it. If used in a middleware-like scenario (where an > arbitrary function is passed to the component, possibly composed with other > functions, and invoked elsewhere), I usually have a convention where I pass > a map of options as an argument to the handler, and make the database a > value in that map. > > > On Wednesday, March 4, 2015 at 12:58:58 PM UTC-5, Colin Yates wrote: >> >> Hi, >> >> I am looking for the Clojure equivalent of: >> >> class Whatever { >> @Transactional >> void doSomething(IDoSomething one, IDoSomethingElse two) { >> one.doSomething() >> two.doSomething() >> } >> } >> >> where both one and two are dependency injected with a proxy which resolves >> to a thread local database connection. In addition, one might itself have a >> collaborator which itself has a collaborator which needs a datasource. >> >> So far I have two protocols: >> >> (defprotocol IDoSomething >> (do-something [this ...]) >> >> (defprotocol IDoSomethingElse >> (do-something [this ...]) >> >> Each protocol may have a number of implementations, one of which is a JDBC >> implementation: >> >> (defrecord JdbcIDoSomething [db] >> (do-something [this ...] ...)) >> >> The problem is that the calling code only gets provided an IDoSomething >> and an IDoSomethingElse and it wants to do something like: >> >> (let [one (->JdbcDoSomething db) two (->JdbcDoSomethingElse db)] >> (with-transaction [tx db] >> (do-something one) >> (do-something-else two))) >> >> The problem here is that the implementations of do-something and >> do-something-else won't have access to the local bound 'tx', they will have >> their own 'db'. >> >> I realise the general argument is to be explicit and pass a db as the >> first argument to the protocol but this isn't appropriate in this case as >> there are validly multiple implementations. I could abstract a >> 'unit-of-work' and pass that as the first argument to the protocols but that >> seems a bit painful. >> >> Also, these protocols may be used quite far away from where the database >> code lives and passing a parameter all the way through the call stack is >> painful. >> >> I am using Stuart Sierra's components if that makes any difference. >> >> I can't be the first person to run into this but google is surprisingly >> unhelpful which makes me think I have missed something fundamental, and that >> I have something upside down. >> >> What do you all do? >> >> > -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to clojure@googlegroups.com > Note that posts from new members are moderated - please be patient with your > first post. > To unsubscribe from this group, send email to > clojure+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/clojure?hl=en > --- > You received this message because you are subscribed to the Google Groups > "Clojure" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to clojure+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
