Creating a WFS Output Format

Adding a new GeoServer WFS output format.

This tutorial applies to GeoServer 1.7.0 and above.
This tutorial assumes you have set up a GeoServer development environment as described in the Maven Quickstart and Eclipse Quickstart

Introduction
Getting Started
Create a New Module
Import Module into Eclipse
Implement CSVOutputFormat
Test CSVOutputFormat
Install the Plug-in

Introduction

This tutorial walks through the process of creating a GeoServer plug-in for a WFS output format using the Comma Separated Value (CSV) file format as an example.

Getting Started

Do a full build from the root of the GeoServer source tree.

[geoserver]% mvn clean install

A successful build should result in teh following output:

[INFO] 
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO] ------------------------------------------------------------------------
[INFO] GeoServer ............................................. SUCCESS [4.985s]
[INFO] GeoServer Maven Plugins ............................... SUCCESS [0.303s]
[INFO] Plugins configuration files ........................... SUCCESS [1.453s]
[INFO] Configuration Deployment PlugIn ....................... SUCCESS [1.659s]
[INFO] GeoServer Maven Archetypes ............................ SUCCESS [0.101s]
[INFO] GeoServer WFS Output Format Archetype ................. SUCCESS [0.198s]
[INFO] Core Platform Module .................................. SUCCESS [1.209s]
[INFO] Data Module ........................................... SUCCESS [4.198s]
[INFO] Open Web Service Module ............................... SUCCESS [4.324s]
[INFO] Main Module ........................................... SUCCESS [10.547s]
[INFO] Web Coverage Service Module ........................... SUCCESS [1.645s]
[INFO] Web Coverage Service 1.1.1 Module ..................... SUCCESS [19.973s]
[INFO] Validation Module ..................................... SUCCESS [0.897s]
[INFO] Web Feature Service Module ............................ SUCCESS [27.089s]
[INFO] Web Feature Service Module ............................ SUCCESS [26.490s]
[INFO] Versioned Web Feature Service Module .................. SUCCESS [2.749s]
[INFO] Web Map Service Module ................................ SUCCESS [32.375s]
[INFO] Web Application Module ................................ SUCCESS [19.315s]
[INFO] Community Space ....................................... SUCCESS [0.126s]
[INFO] GeoServer Extensions .................................. SUCCESS [0.120s]
[INFO] ------------------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2 minutes 45 seconds
[INFO] Finished at: Tue Aug 19 18:55:13 MDT 2008
[INFO] Final Memory: 40M/63M
[INFO] ------------------------------------------------------------------------

Create a New Module

The first step is to create a new module for the output format. This is accomplished by using an GeoServer "archetype", a tool used to create the skeleton of a GeoServer plug-in.

Somewhere on the file system execute the following maven command line:

[/home/bob]% mvn archetype:create -DarchetypeGroupId=org.geoserver.maven \
   -DarchetypeArtifactId=geoserver-archetype-wfsoutputformat \
   -DarchetypeVersion=1.7.0-SNAPSHOT -DgroupId=org.geoserver \
   -DartifactId=csv

The command will create a new directory named csv. The structure of the module should look like:

csv/
 |--pom.xml
 |--src/
     |--main/
     |   |-java/
     |       |-org/
     |          |-geoserver/
     |               |-MyOutputFormat.java
     |--test/
     |   |--java/
     |       |--org/
     |           |--geoserver
     |                 |-MyOutputFormatTest.java
     |--resources/
     |   |-applicationContext.xml

Import Module into Eclipse

1. Change directory into the csv module create the Eclipse project files by executing the command line:

   [csv]% mvn eclipse:eclipse

2. Start Eclipse and import (File->Import...) the csv module. Full instructions are available in the Eclipse Quickstart.

Refactor

1. Using the Eclipse Refactor tool:
   1. Rename the class MyOutputFormat to CSVOutputFormat
   2. Rename the test class MyOutputFormatTest to CSVOutputFormatTest
2. Open the file src/main/resources/applicationContext.xml in the text editor and change:

   <bean id="myOutputFormat" class="org.geoserver.MyOutputFormat"/>

   to:

   <bean id="csvOutputFormat" class="org.geoserver.CSVOutputFormat"/>

   

Implement CSVOutputFormat

1. Open CSVOutputFormat in the text editor.
2. Implement the constructor:

   public CSVOutputFormat() {
         //this is the name of your output format, it is the string
         // that will be used when requesting the format in a 
         // GEtFeature request: 
         // ie ;.../geoserver/wfs?request=getfeature&outputFormat=myOutputFormat
         super("csv");
    }

3. Implement getMimeType():

   @Override
    public String getMimeType(Object value, Operation operation)
               throws ServiceException {
         // return the mime type of the format here, the parent 
         // class returns 'text/xml'
         return "text/csv";
    }

4. Implement write():

   @Override
   protected void write(FeatureCollectionType featureCollection,
             OutputStream output, Operation getFeature) throws IOException, ServiceException {
        //write out content here
           
        //create a writer
        BufferedWriter w = new BufferedWriter( new OutputStreamWriter( output ) );
           
        //get the feature collection
        FeatureCollection fc = (FeatureCollection) featureCollection.getFeature().get(0);
           
        //write out the header
        SimpleFeatureType ft = (SimpleFeatureType) fc.getSchema();
        for ( int i = 0; i < ft.getAttributeCount(); i++ ) {
            AttributeDescriptor ad = ft.getDescriptor( i );
            w.write( ad.getLocalName() );
               
            if ( i < ft.getAttributeCount()-1 ) {
               w.write( "," );
            }
        }
        w.write( "\n" );
           
        //write out the features
        FeatureIterator i = fc.features();
        try {
            while( i.hasNext() ) {
                SimpleFeature f = (SimpleFeature) i.next();
                for ( int j = 0; j < f.getAttributeCount(); j++ ) {
                    Object att = f.getAttribute( j );
                    if ( att != null ) {
                        w.write( att.toString() );
                    }
                    if ( j < f.getAttributeCount()-1 ) {
                        w.write(",");    
                    }
                }    
                w.write( "\n" );
            }
        }
        finally {
            fc.close( i );
        }
           
        w.flush();
    }

5. Save changes.

Test CSVOutputFormat

1. Open CSVOutputFormatTest in the text editor.
2. Modify testOutputFormat(), changing the value of the "outputFormat" parameter to "csv":

   //execute a mock request using the output format
   public void testOutputFormat() throws Exception {
       InputStream in = get( "wfs?request=GetFeature&typeName=sf:PrimitiveGeoFeature" +
           "&outputFormat=myOutputFormat");
       print( in );
   }

3. Save changes.
4. Run the test case. This should result in the following output:

   the_geom,FID,ADDRESS
   MULTIPOLYGON (((0.0008 0.0005, 0.0008 0.0007, 0.0012 0.0007, 0.0012 0.0005, 0.0008 0.0005))),113,123 Main Street
   MULTIPOLYGON (((0.002 0.0008, 0.002 0.001, 0.0024 0.001, 0.0024 0.0008, 0.002 0.0008))),114,215 Main Street

Install the Plug-in

1. From the command line preform a build of the csv module:

   [cvs]% mvn clean install

2. Copy the file csv/target/csv-1.0-SNAPSHOT.jar into the webapps/geoserver/WEB-INF/lib directory of a GeoServer installation:

   [csv]% cp target/csv-1.0-SNAPSHOT.jar /home/bob/geoserver/webapps/geoserver/WEB-INF/lib

3. Restart GeoServer.