Pratik Patel

By Pratik Patel

Doing basic Object-to-Relational Mapping is fun and easy with JPA. Annotate your persistent classes, define a couple of configuration parameters, and you're off and running. This session starts with a basic object model and adds persistence using annotations. Learn how to do mappings for your object model for simple and complex relationships. Also learn how to map Java5 constructs like Enumerations.

Unit testing with JPA can be tricky. Where do you use mock objects? How can I structure my unit tests to exercise my DAO's effectively? How do I unit test JPAQL? Do I need to enhance or can I use a LoadTimeWeaver in my unit tests? This presentation will show, using live code examples, how to effectively unit test JPA components so developers can have confidence in the code they build using JPA.

Now that we have some tests, we'll get into querying for data using JPA. JPA uses JPAQL, or the Java Persistence API Query Language. JPAQL is the object-oriented, rather than standard SQL, way of querying your persisted objects/data. Using many live code examples, developers will gain an understanding of how to write JPAQL. We'll also explore the very useful bulk update & delete feature of JPAQL.

By Pratik Patel

As with many technologies, the basics are easy. The hard part comes when the developer needs to do sophisticated integration, development, and testing as part of an enterprise application. A large enterprise application requires the developer to think of issues that affect the development, scalability and robustness of the application. This presentation will cover the advanced topics described below.

A large enterprise application often will have several sub-projects that each contain their own JPA persistence unit. This opens up a number of questions around how to organize the persistence units and how the code between sub-projects should interoperate. Developers will gain insight into these issues and will see a couple of solutions using live code examples.

Many enterprise applications require integration with an application server's JTA mechanism. JTA integration allows for JPA components to work with container managed transactions and distributed transactions. A typical usage scenario for JPA & JTA is this: read from a database using JPA, perform some business logic, put a message on a queue, write to the database (again using JPA). A JTA transaction allows you to ensure that the entire set of operations is committed or a rollback is performed. In this presentation, the developer will understand the limitations and configuration of using JTA and JPA together ? primarily through real code examples.

Once unit tests are written, developers often gloss over doing fine-grained integration testing just for their persistence layer. Integration testing with JPA means simply one thing: running your JPA components against your target database, for example, Oracle. Overlooking this aspect leads to problems being discovered later in the test cycle (UAT for example) and makes it more difficult to find and fix bugs. This presentation will use live code examples to explain a strategy for getting integration testing for free by reusing unit tests.

Using optimistic locking versus pessimistic locking seems clear cut to most developers. However, a full understanding of the issues with using pessimistic, or datastore, locking is required before making this decision. Developers will get information in the trade offs when using strategy or the other, and how these strategies can be used together with the same persistence unit.

Other tips such as fetch groups, flushing, and caching will be covered as time allows. The presentation will use Weblogic application server, OpenJPA/Kodo, and Spring as the basis for the examples. The presenter has experience with using both Hibernate and OpenJPA so can speak to the portability of these two JPA implementations and its affect on coding.