Working With The Catalog

In this tutorial you will learn how to interact with the GeoServer catalog. The target is to Create a simple service which queries the catalog for data stores and feature types.

So first we create our service, lets call it CatalogLister which will perform the following operations:

Listing all data stores in the catalog
Listing all feature types in the catalog

public class CatalogLister {

    public void listDataStores( OutputStream output ) {
    }

    public void listFeatureTypes( OutputStream output ) {
    }

}

The first thing that is needed is a reference to the catalog itself. So lets add a constructor which takes the catalog as its only paramter.

GeoServerCatalog catalog;

public CatalogLister( GeoServerCatalog catalog ) {
    this.catalog = catalog;
}

First up is listDataStores. A data store corresponds to a service in the catalog. In catalog terminology, one must "resolve a service handle into a data store". Implementing this operation, we step through each service and test for a resolve to a data store. When we find a service that is indeed backed by a data store it is printed out.

public void listDataStores( OutputStream output ) {
    //output
    PrintStream printer = new PrintStream( output );

    //get all services from the catalog
    List services = catalog.members( null );
    for ( Iterator s = services.iterator(); s.hasNext(); ) {
        Service service = (Service) s.next();

        //first we must test to see wether this handle is backed by a datastore
        if ( service.canResolve( DataStore.class ) ) {
            //it is a data store, write it to output
            printer.println( service.getIdentifier().toString() );
        }
    }
}

Next up is listFeatureTypes. A feature type corresponds to a geo resource in the catalog. In the catalog hierarchy geo resources are children or services. So for each service in teh catalog, we check each geo resource for a resolve to a feature type. This time we will go a step further, and actually perform the resolve to underlying feature type object.

public void listDataStores( OutputStream output ) {
    //output
    PrintStream printer = new PrintStream( output );

    //get all services from the catalog
    List services = catalog.members( null );
    for ( Iterator s = services.iterator(); s.hasNext(); ) {
        Service service = (Service) s.next();

        //get all children
        List geoResources = service.members( null );
        for ( Iterator g = geoResources.iterator(); g.hasNext(); ) {
            GeoResource geoResource = (GeoResourfce) g.next();

            //do the test
            if ( geoResource.canResolve( FeatureType.class ) ) {
                //do the resolve
                FeatureType featureType = (FeatureType) geoResource.resolve( FeatureType.class, null );

                printer.println( featureType.getTypeName() );
            }

        }
        
    }
}