Ah finally, thanks John, the "with-open" pattern was indeed the missing
piece: it works!
Just to summarize, here's what works for me:
(extend-type org.postgresql.jdbc4.Jdbc4Array
json/JSONWriter
(-write [o out]
(json/-write (.getArray o) out)))
; plus any other additional required custom JSON writers
(java.sql.Timestamp, Date, etc)
(with-open [conn (jdbc/get-connection *db*)]
(json/write-str
(jdbc/query {:connection conn}
["select * from <table with PG array in it>.."])))
On Wednesday, October 2, 2013 12:06:44 AM UTC-4, John Hume wrote:
>
> I don't use clojure.java.jdbc, so this may be non-idiomatic or just wrong,
> but have you tried something like
>
> (with-open [connection (jdbc/db-connection *db*)]
> (json/write-str
> (jdbc/query {:connection connection}
> ["SELECT * FROM..."])))
>
>
>
> On Tue, Oct 1, 2013 at 8:13 PM, Christian Jauvin
> <cja...@gmail.com<javascript:>
> > wrote:
>
>> Hi Philippe,
>>
>> The Jdbc4Array that's causing me trouble is not the "outer" one,
>> returned from jdbc/query: that one seems to be properly handled by
>> json/write-str.
>>
>> The problem happens with a Postgres table containing a text[] column:
>>
>> create table something (
>> something_id serial primary key,
>> list_of_something text[]
>> )
>>
>> In that case the query returns an ("inner") array for each record, and it
>> gets converted to a Jdbc4Array, which, when passed to the JSON writer,
>> causes the problem.
>>
>> Querying a table without a PG array works perfectly fine though.
>>
>>
>>
>> On Tuesday, October 1, 2013 4:21:33 PM UTC-4, Philippe Guillebert wrote:
>>
>>> Hi,
>>>
>>> You probably need to realize your query using (doall (jdbc/query ...))
>>>
>>> Also, I was wondering, depending on your needs, you could convert
>>> Jdbc4Array into a native type (vector ?) as a post-processing function
>>> of your query and forget about registering JSON writers.
>>>
>>>
>>>
>>> On Tue, Oct 1, 2013 at 9:00 PM, Christian Jauvin <cja...@gmail.com>wrote:
>>>
>>>> Hi Roman,
>>>>
>>>> This approach works for java.sql.Timestamp, which was another type for
>>>> which a JSON writer wasn't defined in my case.
>>>>
>>>> For org.postgresql.jdbc4.**Jdbc4Array however, there's something
>>>> missing, because I get:
>>>>
>>>> *org.postgresql.util.PSQLException: This connection has been
>>>> closed.*
>>>>
>>>> As the person answering me on Stack Overflow suggested, it seems that
>>>> the resultset should be somehow processed before the connection is closed,
>>>> but I really don't know how to do given the construct I'm currently using:
>>>>
>>>> (json/write-str
>>>> (jdbc/query *db*
>>>> ["SELECT * FROM .."]))
>>>>
>>>> where and how could I intercept the resultset that way? Thanks.
>>>>
>>>>
>>>>
>>>> On Tuesday, October 1, 2013 12:49:10 PM UTC-4, r0man wrote:
>>>>>
>>>>> I think you need to implement the JSONWriter protocol for the
>>>>> Jdbc4Array class, and possibly for the datatypes that are in the
>>>>> array. This for example makes the json library aware of
>>>>> java.util.Date classes.
>>>>>
>>>>> (extend-type java.util.Date
>>>>> JSONWriter
>>>>> (-write [date out]
>>>>> (-write (str date) out)))
>>>>>
>>>>> Something like this (not tested):
>>>>>
>>>>> (extend-type org.postgresql.jdbc4.**Jdbc4Arra**y
>>>>> JSONWriter
>>>>> (-write [array out]
>>>>> (-write (seq (.getArray array)) out)))
>>>>>
>>>>> Roman
>>>>>
>>>>>
>>>>> On Tuesday, October 1, 2013 3:57:02 PM UTC+2, Christian Jauvin wrote:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> I asked this question on Stack Overflow yesterday:
>>>>>>
>>>>>> I want to jsonify the results of a query performed against a Postgres
>>>>>> table containing a column of type text[], but the problem is that
>>>>>> clojure.data.json.write-str doesn't seem to know how to handle PG
>>>>>> arrays:
>>>>>>
>>>>>> *Exception Don't know how to write JSON of class
>>>>>> org.postgresql.jdbc4.Jdbc4Array clojure.data.json/write-generic*
>>>>>>
>>>>>> Do I have to supply a custom handler, or is there a simpler way?
>>>>>>
>>>>>>
>>>>>> http://stackoverflow.com/**quest**ions/19103870/jsonify-a-**jdbc4a**
>>>>>> rray-in-clojure<http://stackoverflow.com/questions/19103870/jsonify-a-jdbc4array-in-clojure>
>>>>>>
>>>>>> I'm asking it here in the hope of getting (maybe) a simpler solution,
>>>>>> or at least one I can implement readily, because the problem I have with
>>>>>> one of the suggestions I received (extending org.postgresql.jdbc4.**
>>>>>> Jdbc4Arra**y to implement the missing function) is that I don't know
>>>>>> how to make it work with my usage pattern, which is simply:
>>>>>>
>>>>>> (json/write-str
>>>>>> (jdbc/query *db*
>>>>>> ["SELECT * FROM ..."]))
>>>>>>
>>>>>> How do I "get the array before the connection is closed" with such a
>>>>>> construct? Is there another way?
>>>>>>
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>>>
>>>
>>>
>>> --
>>> Philippe
>>>
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> http://elhumidor.blogspot.com/
>
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