The information in this guide is only needed if you want to perform your own WFS request, for example a
Setting up a WFS client
To set up a connection to a WFS service you first need to create a new WFS client:
String serverURL = "https://sampleservices.luciad.com/wfs"; TLcdWFSClient wfsClient = TLcdWFSClient.createWFSClient(new URI(serverURL));
You can use one client instance for just one OGC service. Therefore, you must identify the service at construction time.
The client you just created will connect with the WFS service by retrieving its capabilities. As described in the OGC specifications, a version negotiation process will also take place to determine a commonly supported version between the web service and the web client.
When a version has been agreed, the corresponding capabilities document is cached locally. To access the document, you can
use the method
Introduction to OGC requests
Creating and sending OGC requests
Requests are modeled by the interface
which supports (if applicable):
Key-value pair requests
You cannot instantiate these request objects directly. Instead, they are created by factory methods in the client.
The created requests are automatically initialized with the parameters
The value of the
VERSION parameter corresponds to the version agreed during the version negotiation
process upon initialization.
Depending on the request, further parameters can or must be defined before sending the request to an OGC service.
The OWS transport layer guide contains more information about the use of
Receiving OGC responses
Each request will have a specific type of response.
The LuciadLightspeed OGC Web Client Suite offer a number of predefined response types.
The general response type
is an extension of
java.io.FilterInputStream, which adds the content type and some extra metadata to the result stream.
Creating OGC custom requests
It is also possible to create custom requests. To support custom requests, you must override the appropriate client class, to provide access to the new requests.
Extensions can perform custom
ILcdOWSRequest implementations by invoking the protected method
Next to the request itself, the name of the operation associated with the request is required. This operation must correspond to an operation defined in the capabilities of the OGC service.
GetCapabilities is a mandatory operation supported by each OGC service.
If the operation is not supported, the request will not be performed and an
UnsupportedOperationException is thrown.
You can retrieve the list of available operations at an OGC service through the method
which returns a list of
Requesting WFS data
Creating and sending WFS requests
The default implementations that model the mandatory WFS requests are:
These request objects cannot be instantiated directly. Instead, they are created by factory methods in
// Create a GetCapabilities request TLcdWFSGetCapabilitiesRequest getCapabilitiesRequest = wfsClient.createGetCapabilitiesRequest(); // Create a DescribeFeatureType request TLcdWFSDescribeFeatureTypeRequest describeFeatureTypeRequest = wfsClient.createDescribeFeatureTypeRequest(); // Create a GetFeature request TLcdWFSGetFeatureRequest getFeatureRequest = wfsClient.createGetFeatureRequest(); // Create a Transaction request TLcdWFSTransactionRequest transactionRequest = wfsClient.createTransactionRequest(); // Create a LockFeature request TLcdWFSLockFeatureRequest lockFeatureRequest = wfsClient.createLockFeatureRequest(); // Create a GetFeatureWithLock request TLcdWFSGetFeatureWithLockRequest getFeatureWithLockRequest = wfsClient.createGetFeatureWithLockRequest();
When the request is configured, it is ready for sending to the WFS. For each predefined request, a separate
method is defined in
TLcdWFSClient that performs the request.
The following code snippet illustrates how to perform the requests:
// Send a GetCapabilities request TLcdWFSCapabilities capabilities = wfsClient.getCapabilities(getCapabilitiesRequest); // Send a DescribeFeatureType request TLcdOWSInputStream describeFeatureTypeResult = wfsClient.describeFeatureType(describeFeatureTypeRequest); // Send a GetFeature request TLcdOWSInputStream getFeatureResult = wfsClient.getFeature(getFeatureRequest); // Send a Transaction request TLcdWFSTransactionResponse transactionResult = wfsClient.transaction(transactionRequest); // Send a LockFeature request TLcdWFSLockFeatureResponse lockFeatureResult = wfsClient.lockFeature(lockFeatureRequest); // Send a GetFeatureWithLock request TLcdOWSInputStream getFeatureWithLockResult = wfsClient.getFeatureWithLock(getFeatureWithLockRequest);
Receiving WFS responses
These response types match the pre-defined requests in
Creating custom WFS requests
The list of available operations at a WFS service can be retrieved through the method
which returns a list of
TLcdOWSOperation objects. By default, it reads the operations defined in the 'Capability/Request' section (version 1.0.0)
or 'OperationsMetadata' (version 1.1.0 and 2.0.0) of the capabilities. If a WFS service uses other sections to define supplementary
operations, in the vendor-specific section for example, you can override this method to take these into account.