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<javascript:>
> > 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.**Jdbc4Array
>>> 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/**questions/19103870/jsonify-a-**
>>>> jdbc4array-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.**
>>>> Jdbc4Array 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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