I don't use OpenJUMP with databases, but these are interesting issues. Jukka wrote: "So what do developers think about what to do with features which do not have geometry? I am remembering that JUMP itself does not necessarily need geometry and I am rather sure that I have even seen such things in OpenJUMP. I quess I got them to OpenJUMP through opening some shapefile."
I don't recall that OpenJUMP can handle having a feature with no geometry. If nothing else, I think it would choke the renderer and would throw a null pointer exception. I could be wrong. Maybe one of the other programmers can comment. I suppose it would be possible to make the renderer ignore features with empty geometries. But there might be other places in the code where empty geometries would throw exceptions. Like when you select a row in an attribute table and then flash the feature on the screen or select it. I do think it is a better idea to return nulls than zeros in most cases. Is the regular Java null suitable for most cases when OpenJUMP is connecting to a database? Would it be better to train OpenJUMP to work with a JDBC null object or a custom object representing a null value from a Database? The Sunburned Surveyor Landon On Thu, Jan 28, 2010 at 12:51 AM, Rahkonen Jukka <jukka.rahko...@mmmtike.fi> wrote: > Hi, > > It would be a correct behaviour to get nulls instead of zeros, I hope you can > fix it. But check what happens if some attribute in a table or in the result > set of a query contains only NULLs. The attribute field should still appear > to OpenJUMP layer schema, and it should be of a correct data type. > > More fundamental question is what to do if geometry field is NULL. It is not > so uncommon situation with databases, and the aim of many GIS projects is > just to add spatial data for existing objects with already known attribute > data by locating them on map. > > At present if the result of a PostGIS query contains only NULL geometries > OpenJUMP throws a Null Pointer Exception. If there are both real geometries > and NULL geometries in the result se, the lines which are missing geometry > are skipped. > > A DB Query Plugin by Larry Reeder is using a workaroud that has been very > usable for me: if geometry is missing the plugin creates a default geometry > as a little rectangle polygon at the origo. By that way user gets the schema > and attributes to OpenJUMP even if the geometry is empty. What is missing is > a clever tool for digitizing the real geometry and inserting it in place of > the default geometry. > > So what do developers think about what to do with features which do not have > geometry? I am remembering that JUMP itself does not necessarily need > geometry and I am rather sure that I have even seen such things in OpenJUMP. > I quess I got them to OpenJUMP through opening some shapefile. > > -Jukka Rahkonen- > > > > Michaël Michaud wrote: > >> >> Hi, >> >> I've got a question for database experts. >> In DatabaseQueryPlugIn, the following JDBC methods are used to get >> numeric attributes from database features >> - ResultSet.getInt() >> - ResultSet.getDouble() >> those methods return an int and a double, even if the >> database contains >> NULL >> NULL : getInt() --> 0 >> NULL : getDouble() --> 0.0 >> I think that OpenJUMP should get a null value each time the database >> contains a NULL value. >> >> If this there is no special reason to use those methods, I'll >> change the >> code to get null instead of 0 in this special cases. >> >> Thanks for any suggestion >> >> Michaël >> >> NB : I noticed another problem with null handling in >> SimpleQueryPlugIn. >> I fixed it in the svn that way : >> select features from layer1 where name = (empty combo box) >> now returns >> empty strings AND nulls (empty strings and null are very similar from >> the end-user point of view) >> I added "is null" as a function to be able to differentiate null from >> empty string cases >> There maybe some corner cases which are still not perfectly handled >> (when there are null in the dataset and the operator is not >> "equal" for >> example) >> >> -------------------------------------------------------------- >> ---------------- >> The Planet: dedicated and managed hosting, cloud storage, colocation >> Stay online with enterprise data centers and the best network >> in the business >> Choose flexible plans and management services without >> long-term contracts >> Personal 24x7 support from experience hosting pros just a >> phone call away. >> http://p.sf.net/sfu/theplanet-com >> _______________________________________________ >> Jump-pilot-devel mailing list >> Jump-pilot-devel@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel >> > > ------------------------------------------------------------------------------ > The Planet: dedicated and managed hosting, cloud storage, colocation > Stay online with enterprise data centers and the best network in the business > Choose flexible plans and management services without long-term contracts > Personal 24x7 support from experience hosting pros just a phone call away. > http://p.sf.net/sfu/theplanet-com > _______________________________________________ > Jump-pilot-devel mailing list > Jump-pilot-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > ------------------------------------------------------------------------------ The Planet: dedicated and managed hosting, cloud storage, colocation Stay online with enterprise data centers and the best network in the business Choose flexible plans and management services without long-term contracts Personal 24x7 support from experience hosting pros just a phone call away. http://p.sf.net/sfu/theplanet-com _______________________________________________ Jump-pilot-devel mailing list Jump-pilot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel
