Rahkonen Jukka a écrit : > 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. > Thanks for your answer. I don't think that a table/layer with only NULLs can be a problem. A database schema and a OJ FeatureSchema can exist and be defined with a datatype even if every value is NULL. > 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. > Ya, interesting problem. > 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. > Interesting ideas. I definitely have to see what the DB Query PlugIn can do. I find Martin's solution with GeometryCollection even more elegant (see a few mails later). I think that OpenJUMP is not ready to work with a layer without geometry or with null geometries. I'm afraid there is much work to make OJ compatible with null geometry or no geometry layers.
Michaël > -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
