Java & SQL, Stronger Together


I’ve recently presented my new talk “Java & SQL — Stronger Together” as a free webinar.

The slides are available as PDF download (10MB), the recording is also available at Vimeo.

Sponsors: ProHuddle and Gitora

This webinar war organized by ProHuddle, Engaging Webinars with IT Professionals, and sponsored by Gitora, Version Control for Oracle.

Key takeaways:

  • Software layers make many tasks easier but don’t expose 100% of the lower layers functionality.

  • What is the right level of abstraction for any given problem?

  • The ORM-cycle: Load data into application, change it there, store changes.

  • Pattern #1: Whenever the cycle is broken, ORM might not be the right layer for this task. Example: Lists.

  • SQL has evolved beyond the relational idea. Recursion is an example for a non-relational operation that can traverse graphs like adjacency lists.

  • We can use native SQL to efficiently load required entities into the persistence context prior to running the actual business logic.

  • If the actual business logic needs an entity that is already in the persistence context, it doesn’t need to run a query to fetch it.

  • Pattern #2: Searching & pre-loading entities with modern SQL can be much more efficient than loading them individually when accessing them.

There are two gotchas that I didn’t mention in the talk:

  • The persistence context is usually accessed by the @Id attribute. If the business logic loads entities by other means, it will typically not be able to use the cached version in the persistence context.

    A few years back I stumbled upon this article which demos an EclipseLink feature for that (@CacheIndex).

  • Running a native query to pre-load entities triggers a flush, which might have negative side effects.

    These queries should be triggered at the very beginning of a transaction, not in the middle. Code re-use might accidentally trigger such a query in the middle of a transaction.

About the Author

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Markus Winand is the SQL Renaissance Ambassador. He is on a mission to introduce developers to the evolution of SQL in the 21st century. Markus can be hired as trainer, speaker and consultant via winand.at.

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