[postgis-users] JAVA and post GIS

[Emily Gouge]

rs.getObject() will return a PGgeometry , so you can cast this to a PGgeometry.  There are some 
examples at the bottom of this page:
http://postgis.refractions.net/docs/ch04.html#id2789526

If you know the PGgeometry is a point, then you can do the following:
PGgeometry g = (PGgeometry)rs.getObject(1);
Point p  = (Point) g.getGeometry();
System.out.println(p.x + ":" + p.y );



Fatemeh Abbasinejad wrote:
> Thanks a loooooooot.This helped.How can I retreive the data inside my database though( the coordinates of my point). With getObject (besides getClass) there aren't a lot of methods? Are we able to cast the object we retreive fron postgis to say " Point" so we can use the getX () and getY() methods?
> 
> Emily Gouge <egouge at refractions.net> wrote:  Fatemeh,
> 
> If you are using an attribute type of Circle you are not using the PostgreSQL data types and not the 
> PostGIS geometry objects. So if you want to use the PostGIS geometry functions you need to create 
> PostGIS Geometry objects using the AddGeometryColumns() function.
> 
> For further information see: http://postgis.refractions.net/docs/ch04.html#id2787299
> 
> 
> The following code will return PGGeometries; however you must have the postgis.jar, 
> postgresql-7.4.1-jdbc3.jar on your class path. If you are using postgres 8.1 then you can have the 
> postgres81 jar in replace of the 7.4.1 jar, however you will note that the addDataType function will 
> be depreciated (the newer version takes a class instead of a String).
> 
> Class.forName("org.postgresql.Driver");
> Connection c= DriverManager.getConnection("jdbc:postgresql://turtle:5432/cwb_devel","egouge", "" );
> ((PGConnection) c).addDataType("geometry", "org.postgis.PGgeometry" ); //for 8.1 change to 
> addDataType("geometry", org.postgis.PGgeometry.class );
> 
> ResultSet rs = c.createStatement().executeQuery("SELECT the_geom from table_name");
> while(rs.next()){
> System.out.println(rs.getObject(1).getClass());
> }
> 
> 
> -Emily
> 
> Fatemeh Abbasinejad wrote:
>> Hi.
>> I sae the code and tried to execute it on my own tables.Ther were some problems:
>> First when trying to add data types it would give me a warning that the method addDataType has been deprecated.
>> Also when I tried to cast to PGeometry it would throw "ClassCastException".Here is my code:
>>
>> ((PGConnection)conn).addDataType("geometry","org.postgis.PGgeometry");
>>
>> Statement s = conn.createStatement(); 
>> ResultSet r = s.executeQuery("select center(geometry)as mycenter from land"); 
>>
>> while( r.next() ) 
>> { 
>> PGgeometry mycenter = (PGgeometry)r.getObject(1); 
>> System.out.println(mycenter.toString()); 
>> }
>>
>> I have a table called "land" which has an attribute "geometry" of type Circle.I want to retreive the center of the circle which is of type "Point".
>> Have I casted wrong? I also tried casting to "Point" but it would give the same exception. What should I do?
>>
>>
>>
>> Emily Gouge wrote:
>> Hi,
>>
>> There is some documentation and an example on connecting to PostGIS using Java. See:
>> http://postgis.refractions.net/docs/ch04.html#id2789526
>>
>> You can add a datatype to the postgres connection and then the getObject() call will return a 
>> PGGeometry object:
>> ((org.postgresql.Connection)conn).addDataType("geometry","org.postgis.PGgeometry");
>>
>> Additionally you can also check out the postgis_jts jar, which provides the ability to return a 
>> JtsGeometry object (and subsequently to convert this object to a JTS Geometry object).
>>
>> Emily
>>
>>
>>
>> Fatemeh Abbasinejad wrote:
>>> I am new to PostGIS. Does anyone know how we can retrieve our defined data types 
>>> (like point,circle,...) from a ResultSet in java. I used getObject but it didn't work. 
>>> -fatemeh
>>>
>>>
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