Preface


The need for persistence is a prerequisite for any enterprise application, and the case is no different for applications written in the Java programming language. A chunk of any typical Java application consists of code that is responsible for storing and retrieving the application-specific data to some type of storage facility so that it can be retrieved and used at a later time.

Java is an object-oriented language, and developers inherently work with objects that, at any time, have states represented by member fields. From the developers perspective, persistence focuses on taking the application-specific information assets, which in fact is just state in these objects, and making them available beyond the lifetime of the virtual machine process. In short, data should be available once the Java virtual machine has exited.

The realization of this notion by developers can take many shapes : extracting and storing the state in a file or in a database using JDBC, using Java serialization and storing the binary representation of the entire object, or the more common enterprise approach of leveraging the facilities of an application server via EJBs to name a few. Irrespective of the technique and the varying degree of complexity involved, each of these approaches has one common conceptual characteristic: the dependence on the developer to extract state information from the objects when it needs to be saved and re-create that state in the object representation when needed by the application.

Now there is a new alternative ”Java Data Objects (JDO) ”that is well placed to change the way developers have traditionally perceived persistence in their applications. JDO is a standard developed under the auspices of the Java Community Process by a number of industry participants . The JDO specifications were the realization of an effort to satisfy the need for a transparent persistence mechanism in Java that would satisfy two orthogonal visions at the same time. One aimed to provide a standard programming interface between application code and the underlying persistent stores like databases and file systems in a manner similar to JDBC; the other aimed to simplify secure and scalable application development by providing a Java-centric mechanism that would allow the manipulation and traversal of persistent objects. JDO satisfies, in fact excels, at both. With JDO, developers can concentrate on designing applications around the intended purpose ”to solve business problems ”rather than around the mechanics of persistence infrastructures .

JDO is fast gaining momentum and acceptance in the community as the preferable means to introduce persistence in Java applications. Developers are learning to appreciate the simplicity and power of this technology, and architects are pleased at the reduced development time. In this book, we not only guide the reader in understanding JDO itself, but help readers learn how to apply this technology effectively in real-world applications.



Core Java Data Objects
Core Java Data Objects
ISBN: 0131407317
EAN: 2147483647
Year: 2003
Pages: 146

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