Hibernate Tips is a series of posts in which I describe a quick and easy solution for common Hibernate questions. If you have a question you like me to answer, please leave a comment below.
My database supports auto-incremented columns. How can I use them as primary keys in Hibernate?
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JPA and Hibernate support different strategies to generated primary key values. One of them is the identity strategy which uses an auto-incremented database column.
If you want to use this strategy, you have to annotate the primary key attribute @Id and with the @GeneratedValue annotation and set the strategy attribute to GenerationType.IDENTITY.
The following code snippet shows an example of this annotation
If you now persist a new Author entity, Hibernate will use the auto-incremented database column to generate the primary key value. You can see that in the log file if you activate the logging for SQL statements.
Databases handle auto-incremented columns very efficiently. But you need to be aware that Hibernate has to perform the INSERT statement immediately to get the primary key value. This prevents it from using different performance optimizations that rely on the delayed execution of database operations.
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Auto-incremented database columns are only 1 out of 4 options to generate primary key values. I get into more details about the different strategies in How to generate primary keys with JPA and Hibernate.
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