The information in this guide is only needed if you want to perform your own WMS request, for example a GetLegendGraphic request. The steps described here are not needed when you only want to visualize the data on a GXY or Lightspeed view.

Setting up a WMS client

To set up a connection to a WMS service you first need to create a new WMS client:

String serverURL = "";
TLcdWMSClient wmsClient = TLcdWMSClient.createWMSClient(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 WMS 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 getCachedCapabilities.

Introduction to OGC requests

Creating and sending OGC requests

Requests are modeled by the interface ILcdOWSRequest, which supports (if applicable):

  • Key-value pair requests

  • XML-encoded requests

  • REST 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 SERVICE, REQUEST and VERSION. 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 ILcdOWSRequest instances.

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 TLcdOWSInputStream is an extension of, 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 performRequest.

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.

For example, 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 decodeOperations, which returns a list of TLcdOWSOperation objects.

Requesting WMS data

Creating and sending WMS requests

The default implementations of ILcdOWSRequest for the WMS service are:

Use the factory methods in TLcdWMSClient to create these request objects.

Program: Creating WMS requests
// Create a GetCapabilities request
TLcdWMSGetCapabilitiesRequest getCapabilitiesRequest = wmsClient.createGetCapabilitiesRequest();

// Create a GetFeatureInfo request
TLcdWMSGetFeatureInfoRequest getFeatureInfoRequest = wmsClient.createGetFeatureInfoRequest();

// Create a GetMap request
TLcdWMSGetMapRequest getMapRequest = wmsClient.createGetMapRequest();

// Create a GetLegendGraphic request
TLcdWMSGetLegendGraphicRequest getLegendGraphicRequest = wmsClient.createGetLegendGraphicRequest();

// Create a DescribeLayer request
TLcdWMSDescribeLayerRequest describeLayerRequest = wmsClient.createDescribeLayerRequest();

Only the GetMap request supports XML encoding in addition to key-value pair encoding. The reason for this is that the XML encoding is not specified for the other requests.

After the configuration of the request, you can send it to the WMS. For each pre-defined request, a separate method is defined in TLcdWMSClient that performs the request. If a service exception is returned by the server, the exception is decoded and thrown as a TLcdOWSServerException. Otherwise the result is returned.

The following code snippet illustrates how to send the requests:

Program: Sending WMS requests
// Send a GetCapabilities request
ALcdOGCWMSCapabilities capabilities = wmsClient.getCapabilities(getCapabilitiesRequest);

// Send a GetFeatureInfo request
TLcdOWSInputStream getFeatureInfoResult = wmsClient.getFeatureInfo(getFeatureInfoRequest);

// Send a GetMap request
TLcdOWSInputStream getMapResult = wmsClient.getMap(getMapRequest);

// Send a GetLegendGraphic request
TLcdOWSInputStream getLegendGraphicResult = wmsClient.getLegendGraphic(getLegendGraphicRequest);

// Send a DescribeLayer request
TLcdOWSInputStream describeLayerResult = wmsClient.describeLayer(describeLayerRequest);

Receiving WMS responses

The pre-defined WMS response types are:

Creating custom WMS requests

The list of available operations at a WMS service can be retrieved through the method decodeOperations, which returns a list of TLcdOWSOperation objects. By default, it reads the operations defined in the 'Capability/Request' section of the capabilities. If a WMS service uses other sections to define supplementary operations, in the vendor-specific section for example, this method can be overridden to take these into account.

If the server uses WMS version 1.3.0, it can also define extra operations by providing an extension schema of the WMS schema in its capabilities. If this is done correctly, the client decodes these operations automatically and adds them to the list.