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

Chapter 5. Location Aware Services 159

The role of a service adapter includes:

򐂰 Interface translation

The service adapter translates the interface that is provided by the service

provider to a Location Aware Services interface.

򐂰 Service invocation and error handling

Adapters invoke services depending on the service provider. It could, for

example, be through TCP/IP sockets, HTTP requests, and so on. Adapters

also act like RPC stubs that serialize and deserialize objects that are used by

location services. Adapters insulate the application developer from the

service protocols.

򐂰 Authentication with service providers

Adapters have to handle the authentication mechanism as required by the

service provider.

In order to enable services through WebSphere Everyplace Access, service

providers have to write their own adapters. Adapters must implement specific

interfaces that are provided by Location Aware Services.

Adapters for the following service providers are already provided with

WebSphere Everyplace Access:

򐂰 Webraska

򐂰 MapInfo

򐂰 Go2Map

򐂰 LIF

5.2.2 Location Aware Services portlet service

The core functionality of the Location Aware Services is handled by the portlet

service, which comprises several components and is the core component in the

Location Aware Services architecture.

A portlet service is a discoverable extension to the Portal functionality. Location

Aware Services are implemented as a portlet service because the life cycle is

managed by the Portal and does not have container restrictions placed on

portlets. Application portlets can query the container for Location Aware Services

and use the service without knowing the implementation or concern themselves

with its life cycle management.

To understand more about portlet services, see IBM WebSphere Portal V5: A

Guide for Portlet Application Development, SG24-6076.

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

The Location Aware Services portlet:

򐂰 Provides appropriate service to the application based on the preferences that

are given by the application through the properties file. This functionality is

taken care by the Location Service Factory.

򐂰 Determines service failures based on service failover policies and takes

appropriate action. This functionality is handled by the Service Binder object.

򐂰 Determines the ordering of service providers who are offering the same

service. If Location Aware Services cannot determine which service provider

to use, then it uses the order set by the administrator for the services.

Location Service Factory

As the name implies, Location Service Factory creates instances of Location

Aware Services adapters when requested. The request for adapters can come

from two sources: applications, via the service binder objects, and internally via

service monitor object when it decides that the particular service adapter is

needed.

The Location Service Factory makes use of the parameters that are supplied to

determine which service provider adapter must be instantiated. For example, for

map services, the parameters might include the coverage region, the format of

the maps, and so on. The Location Service Factory that is based on these

parameters provides the best-fit service provider. If there is a conflict because

several providers provide the requested features, then the order set by the

administrator is taken.

Service Binder objects

Service Binder objects provide the point at which Location Aware Services

mediates access to location services. To the application, these objects offer the

interfaces of specific location services. Internally, they make use of Location

Service Factory functions to instantiate adapters. Service Binder objects also

handle service failure based on failover policies and replace services.

Service Monitor

This monitors the status of all the current services and notifies the Service Binder

if any of the service fails so that the failed service can be replaced by other

service providers.

Service Registry

The Service Registry is a repository of service descriptions and other service

data, including authentication credentials. Service descriptions contain

information that Location Aware Services require to manage the service,

including a unique name (within the Location Aware Services installation) and