[Mapbender-users] Create points with a geoserver WFS-T

[Sebastian Krohn-Grimberghe]

Hello Daniel,

> If I unstand you correctly, I have to write a function in my PostgreSQL
> database. I never programmed a function in PostgreSQL by my
> self...should this be sth. like a Trigger: so the Trigger startet after
> the user created the object?! and wrote the message? and stop the
> action
> saving the new point in my database!

You are right... You can create a trigger for your geometry table, which is
called when GeoServer inserts a new geometry into the table. There you can
check with PostGIS functions if the new (buffered) point intersects other
geometries. If the point intersects another geometry you can raise an
exception. By raising the exception the new point will not be stored in the
database and GeoServer should receive and pass a failure message. 

The trigger function could look like this:

CREATE OR REPLACE FUNCTION my_trigger_function() RETURNS trigger AS
 $$
   DECLARE
	-- declare variables
      current_row RECORD;
   BEGIN
	-- get all existing geometries which intersect the new geometry
(NEW.the_geom) 
	-- around the new geometry is a buffer of 50 meters (or whatever
your unit is)
      FOR current_row IN SELECT * from my_geom_table t WHERE
ST_Intersects(ST_Buffer(NEW.the_geom, 50),t.the_geom) LOOP
		-- intersection found
		RAISE EXCEPTION 'my error message';
      END LOOP;

	-- no intersection, new geometry will be inserted
      RETURN NEW;
   END;
 $$ LANGUAGE 'plpgsql';

CREATE TRIGGER my_trigger BEFORE INSERT OR UPDATE ON my_geom_table FOR EACH
ROW EXECUTE PROCEDURE my_trigger_function();


I use a similar trigger with an OpenLayers client. When an exception is
raised, GeoServer returns XML with a failure information. But the message is
always the same, so it is not affected by the error message in the trigger
function. I do not know how the error messages of WFS transactions are
handled by Mapbender. So I cannot help you with this yet, but I hope this
helps you with the database part.


Best regards,
Sebastian

--
Sebastian Krohn-Grimberghe
Entwicklung

IP SYSCON GmbH

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