Chapter 5 Client Design

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Figure 5.4

J2ME Client Accessing Web Service

J2ME clients may access Web services using a subset of the JAX RPC API.

When accessing Web services, J2ME clients should consider network connection

and bandwidth issues, offline versus connected operation, and GUI and process 

ing limitations.

Networks supporting J2ME devices may not always provide consistent con 

nectivity. Applications using such networks must consider connection failure, or

sporadic connectivity, and be designed so that recovery is possible. 

Additionally, the bandwidths for many networks supporting J2ME devices

limit the rate at which data can be exchanged. Applications need to be designed to

limit their data exchange rate to that allowed by the network and to consider the

cost that these limitations imply. Care must also be taken to deal with network

latency to keep the user experience acceptable. Since Web services do not specify

a level of service for message delivery, the client application must take this into

account and provide support for message delivery failures.

Keep in mind that J2ME network providers may charge for network usage by

the kilobyte. J2ME targeted applications may be expensive for the user unless

care is taken to limit the data transferred.

Applications for J2ME devices may work in an offline, or disconnected, mode

as well as an online, or connected, mode. When working in an offline mode, appli 

cations should collect data and batch it into requests to the Web service, as well as

obtain data from the service in batches. Consideration should be given to the

amount of data that is passed between the Web service and the client.