IBM WebSphere Everyplace Access V5 Handbook for Developers and Administrators Volume IV: Advanced Topics

Chapter 6. Location Aware Services application development 217

19.Finally the MappingService is used to request the map specifying the bounds,

the mapping options, and the overlay. The Map object represents a map that

includes image data, width, height, and format, and the geographical area

covered by the map.

Example 6-9 Requesting the map

Map map = mappingService.getMap(bounds, options, overlays);

20.The Map.getData() returns the map as a byte array. This can be used to

render the map on a canvas, save it as a GIF file and render it as an HTML

and so on.

6.4 Developing a Location Aware Services adapter

Location Aware Services uses adapters that can be dynamically plugged in for

enabling services from service providers. Service providers should write custom

adapters that communicate with their infrastructure to provide the necessary

service. Location Aware Services provides adapters for several service

providers. See Chapter 5, “Location Aware Services” on page 155 for a list of

supported service providers.

In order to enable Location Aware Services to use your custom adapter to

provide the service, you should develop the adapter in accordance with the

interfaces defined and register the adapter for the specific service.

All service adapters for Location Aware Services must extend the

com.ibm.atlas.adapters.LocationServiceAdapter class.

The LocationServiceAdapter class is an abstract class that contains the following

methods:

򐂰 public void init(LocationServiceConfig config)

򐂰 public LocationServiceConfig getConfig()

򐂰 public void setClientOptions(ServiceRequestOptions options)

򐂰 public abstract ServiceCapabilities getCapabilities()

The Location Service Factory calls the init method when the adapter is first

created. The adapter can override this method to perform any required

initialization procedures, including authentication if it is session-based, or testing

communication with the remote provider's site. If the adapter overrides this

method, it should call super.init first. The setClientOptions method sets the

clientName, clientPassword and userLanguagePreference properties in the

ServiceRequestOptions object to values given in the adapter's init properties or,

218 IBM WebSphere Everyplace Access V5, Volume IV: Advanced Topics

if not given there, to defaults specified in the atlas.properties file. All adapters

must call this method when their main service methods are invoked.

The getCapabilities method returns a service-specific subclass of

ServiceCapabilities. A DirectoryServiceAdapter must return a

DirectoryCapabilities object, a GeocodingServiceAdapter must return a

GeocodingCapabilities object, and so on. Since the ServiceCapabilities

subclasses provide constructors that take a Properties object as a parameter,

each adapter's responsibility is to retrieve the service's properties from the

Service Registry and pass them to the constructor. Thus, a MappingService

adapter's getCapabilities method would typically be implemented as illustrated in

Example 6-10.

Example 6-10 Sample MappingService adapter’s getCapabilities method

ServiceCapabilities getCapabilities() {

ServiceRegistry svcReg = config.getFactory().getServiceRegistry();

Properties svcProps = svcReg.getServiceProperties(config.getName());

return new MappingCapabilities(svcProps);

}

For location service providers that offer two or more of the Location Aware

Services, it may be desirable to create a superclass that is extended by all the

provider's service adapters. This superclass would extend

LocationServiceAdapter and would typically handle the low-level communication

with the service provider that is common to all the adapters.

Depending on the type of service, service adapters should implement one of the

service interfaces. These service interfaces are defined in the com.ibm.adapters

package. The following interfaces are included in this package:

򐂰 DevicePositionServiceAdapter

򐂰 DirectoryServiceAdapter

򐂰 GeocodingServiceAdapter

򐂰 MappingServiceAdapter

򐂰 ReverseGeocodingServiceAdapter

򐂰 RoutingServiceAdapter