For a simple many-to-many database relationship, you can use the
@ManyToMany JPA annotation and, therefore, hide the join table.
However, sometimes you need more than the two Foreign Key columns in the join table, and, for this purpose, you need to replace the
@ManyToMany association with two bidirectional
@OneToMany associations. Unlike unidirectional
@OneToMany, the bidirectional relationship is the best way to map a one-to-many database relationship that requires a collection of Child elements on the parent side
In this article, we are going to see how you can map a many-to-many database relationship using an intermediary entity for the join table. This way, we can map additional columns that would be otherwise impossible to persist using the
@ManyToMany JPA annotation.
Continue reading “The best way to map a many-to-many association with extra columns when using JPA and Hibernate”
As previously explained, CDC (Change Data Capture) is one of the best ways to interconnect an OLTP database system with other systems like Data Warehouse, Caches, Spark or Hadoop.
Debezium is an open source project developed by Red Hat which aims to simplify this process by allowing you to extract changes from various database systems (e.g. MySQL, PostgreSQL, MongoDB) and push them to Apache Kafka.
In this article, we are going to see how you can extract events from MySQL binary logs using Debezium.
Continue reading “How to extract change data events from MySQL to Kafka using Debezium”
I either have time for reading or writing, but not both. Now that the first edition of High-Performance Java Persistence is done, I can catch up on the many books I planned on reading but didn’t have time to do so.
In this post, I’m going to review High Performance MySQL by Baron Schwartz, Peter Zaitsev, and Vadim Tkachenkoa, which is a must-read book for anyone working with MySQL.
Continue reading “Book Review – High Performance MySQL (3rd edition)”
Now that the JPA 2.2 Review Ballot was approved, let’s start analyzing some of the new additions to the standard which have been supported by Hibernate for quite some time already. In this article, we are going to see how the JPA 2.2 Stream query results are supported by Hibernate and the caveats of using database cursors just to limit the amount of data that needs to be fetched.
Continue reading “What’s new in JPA 2.2 – Stream the result of a Query execution”