[postgis-users] How do I handle a ResultSet from a java request?

Nicolas Ribot nicolas.ribot at gmail.com
Tue Oct 6 07:01:45 PDT 2015


What kind of client is plugged to your Java code ?
Does it expect a raw json document to process on its own, or a geographic
object built in Java ?

Nicolas

On 6 October 2015 at 15:55, Andrew Davis <drsockmonkee at gmail.com> wrote:

> Thanks...
> I am just starting out on it.  I will be passing only about 40 point
> features first.
>
> I will make note of and go look at the stream... as well..
>
> Andy
> On Oct 6, 2015 8:53 AM, "Nicolas Ribot" <nicolas.ribot at gmail.com> wrote:
>
>> Hi Andy,
>>
>> Your Java ResultSet contains one big row representing your geoJson
>> document. You can pass it to the client by building a string from the
>> resultset:
>> String geojson = resultSet.getString(1);
>>
>> Be careful to the potential big size of the String: if you expect a big
>> geojson document from the database, it may be wiser to stream it to the
>> client from the JDBC connection instead of building a Java String.
>>
>> Nicolas
>>
>> On 6 October 2015 at 15:32, Andrew Davis <drsockmonkee at gmail.com> wrote:
>>
>>> Hi all..
>>>
>>> I'm sending my first question out so patience please.
>>>
>>> I've got a working servlet on my server that will query for and get
>>> information back from my postgis DB.
>>>
>>> Up until now I have been just parsing the results and sending back a
>>> json string.  I want to get a GeoJSON back from my db now.
>>>
>>> I've been working through the information I found here:
>>>
>>> http://www.postgresonline.com/journal/archives/267-Creating-GeoJSON-Feature-Collections-with-JSON-and-PostGIS-functions.html
>>>
>>> I can create the table with locations included and a geog value, and I
>>> can run the query below
>>>
>>> SELECT row_to_json(fc)
>>>  FROM ( SELECT 'FeatureCollection' As type, array_to_json(array_agg(f)) As features
>>>  FROM (SELECT 'Feature' As type
>>>     , ST_AsGeoJSON(lg.geog)::json As geometry
>>>     , row_to_json((loc_id, loc_name)) As properties
>>>    FROM locations As lg   ) As f )  As fc;
>>>
>>>
>>> which brings back a single line string and is in the correct format all in PGAdmin3.
>>>
>>>
>>> I have been trying to duplicate this from my server with java and am stuck at the point where I have
>>>
>>> run the query and have a 'thing' (ResultSet) but am unsure as to how to handle it and then pass it
>>>
>>> back to the client.
>>>
>>>
>>> Any help would be welcome.
>>>
>>>
>>> Andy..
>>>
>>>
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>>>
>>
>>
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