1. Java Open Source GIS
Development
From the building blocks to extending
an existing GIS application.
Geoinformation Research Group, Department of Geography
University of Potsdam
August 2011
Part 1: Introduction and main tools
Tutor: Andrea Antonello
ydroloGIS nvironmental ngineering
HydroloGIS S.r.l. - Via Siemens, 19 - 39100 Bolzano www.hydrologis.com

2. Who am I?
Andrea Antonello
Environmental Engineer, graduated with GRASS development thesis
PhD in Environmental Sciences, working on development of digital
field mapping tools
GIS development
Involved for years in open source GIS development, mainly GRASS,
JGrass, uDig, BeeGIS, Geopaparazzi
HydroloGIS
Work for HydroloGIS, a company that writes and uses GFOSS
products for environmental analyses, mostly hydrology and
geomorphology.

3. Buzzwords: Java, Maven and Eclipse
Java
The Java technology is a programming language and a platform.
Maven
Maven is build system for Java which is very good at managing
dependencies.
Eclipse IDE
Eclipse is a popular integrated development environment most often
used for all kinds of Java development.
Eclipse RCP
The rich client platform used to build applications like uDig, but also
the eclipse IDE itself.

4. Buzzwords: GeoTools, JTS and OGC
GeoTools
GeoTools is an open source (LGPL) Java code library which provides
standards compliant methods for the manipulation of geospatial data,
for example to implement Geographic Information Systems (GIS).
Java Topology Suite
The JTS Topology Suite is a library of spatial predicates and
functions for processing geometry.
Open Geospatial Consortium
The OGC is a non-profit, international, voluntary consensus
standards organization that is leading the development of standards
for geospatial and location based services.

5. Buzzwords: uDig, OMS and JGrasstools
User-friendly Desktop Internet GIS
uDig is an open source (LGPL) desktop GIS, built with Eclipse Rich
Client (RCP) technology.
Object Modeling System
The OMS object-oriented modeling framework. OMS allows model
construction and model application based on components.
JGrasstools
A geospatial processing library based on OMS that works in uDig's
Spatial Toolbox.

6. Useful spatial links
Spatial:
• GeoTools Homepage
• uDig Homepage
• OMS3 Homepage
• JGrasstools Homepage
• Imageio-ext Homepage
• JTS Homepage

7. Useful development links
Java and friends:
• Java Downloads / Java Instructions
• JAI Core Homepage / JAI Core Downloads / JAI Core Instructions
• JAI ImageIO Homepage / JAI ImageIO Downloads / JAI ImageIO
Instructions
• Maven Homepage
• Eclipse HomePage

8. Contents of the course
Part 1: Introduction and main tools
• setup of java, eclipse, maven
• introduction to the GeoTools project
• introduction to the Natural Earth project
• creation of a simple GeoTools based project
• visualization of a map

9. Part 2: Introduction of the main Geo-Objects
• geometry objects
• projections
• vector objects
• raster objects
• filters
• style

10. Part 3: Vector data
• vector basics, handling shapefiles
• geometry basics
• predicates
• functions
• tips and tricks

11. Part 4: Raster data
• reading/writing raster data
• processing rasters
• image vs. world space

12. Part 5: Integrating with uDig
• introduction to OMS
• introduction to uDig
• introduction to uDig's Spatial Toolbox
• introduction to jgrasstools
• create example OMS GeoTools based modules

13. Preparing the development environment
Java Installation
Perform the following installations, based on the download and instructions
links supplied in the previous section:
• Java Development Kit (JDK)
• Java Advanced Imaging (JAI core), used by GeoTools for raster support
• JAI ImageIO, used to read and write raster files
• ImageIO-ext, used to support raster formats through gdal drivers:

14. Eclipse Installation
1. Visit the Eclipse HomePage and download Eclipse IDE for Java
developers.
2. Eclipse does not provide an installer, just unzip to a directory run.
3. To start out create a folder /home/moovida/giscourse/ somewhere
on your disk to keep all our java development in one spot. To keep an
existing reference we will use /home/moovida/ as base, which should
be substituted with a folder of choice.
4. Unzip the downloaded file to your /home/moovida/giscourse/ folder,
which will create /home/moovida/giscourse/eclipse/.
5. Open up the eclipse.ini file and changing the Xmx argument to
-Xmx2000m, if you have enough RAM.
6. Run the eclipse executable.

15. 7. When you start up eclipse for the first time it will prompt you for a
workspace. To keep our java work in one spot you can type in:
/home/moovida/giscourse/eclipse/workspace
8. On the Welcome view press Workbench along the right hand side and we
can get started

16. Maven Installation
The maven build tool can work on the command line and includes a plugin
for generating eclipse .project and .classpath files.
1. Download Maven from the Maven Homepage
During the course we will use Maven 2.2.1.
2. Unzip the file apache-maven-2.2.1-bin.zip to
/home/moovida/giscourse/apache-maven-2.2.1/.
3. You need to have a couple of environmental variables set for maven to
work. Open inside your favourite text editor the .bashrc file inside you
home folder and add the following lines at the end (if similar ones are
not there already):

17. JAVA_HOME /home/moovida/java/jdk1.6.0_16
M2_HOME /home/moovida/giscourse/apache-maven-2.2.1/
PATH $PATH:$JAVA_HOME/bin:$M2_HOME/bin
4. Open up a terminal
5. Type the following command to confirm you are set up correctly:
mvn -version

18. 6. This should produce something like:
Apache Maven 2.2.1 (r801777; 2009-08-06 21:16:01+0200)
Java version: 1.6.0_14
Java home: /home/moovida/SOFTWARE/JAVA/JDKS/jdk1.6.0_14/jre
Default locale: en_US, platform encoding: UTF-8
OS name: "linux" version: "2.6.38-8-generic" arch: "amd64" Family: "unix"

19. Setting up the example project in Eclipse
To get started quickly we will use a template project that already contains the
dependencies we will need. The example project can be downloaded from:
http://jgrasstools.googlecode.com/files/jgt-dev-example.tar.gz
Create the folder /home/moovida/giscourse/code/ that will hold all the
code we will write during the course. Extract the downloaded package into
the code folder (tar zcvf jgt-dev-example.tar.gz). You now have
the folder: /home/moovida/giscourse/code/jgt-dev-example.

20. If starting from scratch, we would have created a new maven project inside
/home/moovida/giscourse/ with the command:
mvn archetype:create -DgroupId=org.geotools -DartifactId=tutorial
and after that we would have added the dependencies to the project's
configuration file.
Starting with an existing project helps to how the dependencies rules work,
without the need to understand all of maven.

21. Dependencies
The downloaded project is a maven project that already contains all the
needed dependencies (the references).
Everything needed is defined inside the pom.xml file in the root of the
project.
A dependency definition looks like:
<dependency>
<groupId>org.jgrasstools</groupId>
<artifactId>jgt-jgrassgears</artifactId>
<version>0.7.1</version>
</dependency>
To find such dependencies when you have no template, websites like:
http://mvnrepository.com/ get handy.

22. Repositories
Most of the packages are kept in a central maven repository. GeoTools'
packages are hosted by the Open Source Geospatial Foundation (Osgeo
Homepage).
Any repository can be added to the pom.xml project file. In our example we
find:
<repository>
<id>maven2-repository.dev.java.net</id>
<name>Java.net repository</name>
<url>http://download.java.net/maven/2</url>
</repository>
<repository>
<id>osgeo</id>
<name>Open Source Geospatial Foundation Repository</name>
<url>http://download.osgeo.org/webdav/geotools/</url>
</repository>

23. Create the Eclipse project
To actually get the dependencies downloaded, we can proceed like the
following:
1. From within /home/moovida/giscourse/code/jgt-dev-example
And ask for our project to be set up for eclipse:
mvn eclipse:eclipse
This will generate the eclipse project files and download the needed jars
for you.
2. Return to Eclipse
3. Use Windows -> Preferences to open the Preference Dialog. Using
the tree on the left navigate to the Java -> Build path ->
Classpath Variables preference page.

24. Load the Eclipse project
4. Add an M2_REPO classpath variable pointing to your local repository,
which is created automatically by maven itself and by default is located in:
/home/moovida/.m2/repository.
5. We can now import your new project into eclipse using File ->
Import
6. Choose Existing Projects into Workspace from the list, and
press Next
7. Select the project you created in:
/home/moovida/giscourse/code/jgt-dev-example.
8. Press Finish to import your project

25. Testing the development environment
Download a test dataset
The best way to check if the development environment is properly installed,
is to show a map. First we need some data to work with. The Natural Earth
data project is a place we can get some freely available datasets. It is
supported by the North American Cartographic Information Society.
Let's download 110m-cultural.zip, which contains various vector layers of
countries, boundaries and cities of the whole world.
create a datafolder: /home/moovida/giscourse/data
and unzip them into it in order to have:
/home/moovida/giscourse/data/110m_cultural

26. Write and run your first GIS application
• copy the following code snippet
import java.io.File;
import org.geotools.data.*;
import org.geotools.data.simple.SimpleFeatureSource;
import org.geotools.map.*;
import org.geotools.styling.*;
import org.geotools.swing.JMapFrame;
import org.geotools.swing.data.JFileDataStoreChooser;
public class Quickstart {
public static void main( String[] args ) throws Exception {
File file = JFileDataStoreChooser.showOpenFile("shp", null);
FileDataStore store = FileDataStoreFinder.getDataStore(file);
SimpleFeatureSource featureSource = store.getFeatureSource();
MapContext map = new MapContext();
map.setTitle("Quickstart");
Style style = SLD.createSimpleStyle(featureSource.getSchema());
Layer layer = new FeatureLayer(featureSource, style);
map.addLayer(layer);
JMapFrame.showMap(map);
}
}
• select the org.jgrasstools.part1 package in the project
• paste the code in (eclipse will create the right class for it)

27. • run the application by right clicking on the class and run as -> java
application
• browse in the filechooser to select the file:
110m_admin_0_countries.shp
You should see the following map:

28. The first (and most boring) step is left behind.
Take a deep breath.
QUESTIONS?

29. This work is released under Creative Commons Attribution Share
Alike (CC-BY-SA)
Much of the knowledge needed to create this training material has
been produced by the sparkling knights of the GeoTools, JTS and
uDig community. Another essential source has been the Wikipedia
community effort.
Particular thanks go to those friends that directly or indirectly helped
out in the creation and review of this developer's handbook: Jody
Garnett from the uDig/GeoTools community and the TANTO team.
This tutorial was written with the support of the Geoinformation
Research Group of the University of Potsdam and HydroloGIS.