Enterprise J2ME Developing Mobile Java Applications [Electronic resources] نسخه متنی

11.1 Database on the Go

One of the biggest obstacles of WAP-based mobile commerce is the requirement of uninterrupted wireless network coverage. Today's unreliable and incomplete wireless network infrastructure leaves the anywhere, anytime promise of mobile commerce unfulfilled. Fortunately, the widespread adoption of the smart mobile client technology will change this picture and enable new generations of mobile applications.

A key benefit of smart clients is that they can function in the offline mode when the wireless network connection is temporarily unavailable. The offline mode drastically improves the application availability. In fact, most of today's mobile applications primarily work in the offline mode. Users carry their PDAs or barcode scanners all day. They synchronize data with desktop computers only once or twice a day. The disconnected mobile application architecture is a proven success.

To support offline operations, the mobile client must store application data locally. There are great needs for first-class data management tools on mobile devices. Lightweight relational databases are just the tools we are looking for. Compared with linear data storage facilities (e.g., plain file or the MIDP RMS) that come with J2ME standard profiles, relational databases are much more efficient for complex data. Besides supporting highly available offline applications, mobile databases offer the following benefits.

They can be used to manage user preferences. Extreme personalization is touted as another major benefit of mobile commerce.

They can provide performance cache to reduce network round trips. This could drastically improve application performance on slow and long latency wireless networks.

The standard API to access relational databases on the J2SE and J2EE platforms is the Java DataBase Connectivity (JDBC) API. To leverage existing developer skills, most mobile database vendors choose to support subsets of JDBC or JDBC-like APIs on J2ME platforms. For the impatient readers, a sample mobile JDBC application is given in Section 11.11 later this chapter. Now, let's have a look at the JDBC API first.