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.
Question:
I use a java.util.Date to persist a date as an entity attribute.
But Hibernate maps it to a timestamp with nanoseconds. How can I change the mapping so that Hibernate only stores the years, months and days?
Solution:
The SQL standard supports three different data types to store date and time information. Hibernate can map all of them to a java.util.Date or a java.util.Calendar. You need to decide which of the following SQL types Hibernate shall use:
- TIMESTAMP: Persists the date and time with nanoseconds. Hibernate uses this type by default.
- TIME: Stores only the time of day without nanoseconds.
- DATE: Persists only the date with years, months and days.
You can define the preferred mapping with the @Temporal annotation. As you can see in the following code snippet, it takes a TemporalType enum as a value. The enum allows you to select the SQL type (DATE, TIME or TIMESTAMP) which you want to use.
As you can see in the following log output, the dateOfBirth attribute of the Author entity gets mapped to an SQL DATE without any time information.
Learn More:
Since Hibernate 5, you can also use the classes Java 8’s Date and Time API as entity attribute types. The new classes solve a lot of issues of the java.util.Date and provide all information Hibernate needs to map them to the correct JDBC types.
I explain the mapping of the Date and Time API classes in more details in: Hibernate 5: how to persist LocalDateTime and Co with Hibernate.
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