Hibernate Tips: How to select multiple scalar values in a Criteria Query

By Thorben Janssen

Criteria API, Query

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:

How can I select a list of scalar values in a Criteria query?

Solution:

The CriteriaQuery interface provides the multiselect() method which allows you to select multiple scalar values. The following code snippet shows an example for such a query.

The multiselect() method expects a List or an array of Selection interfaces which define the entity attributes which shall be fetched from the database. In this example, I use the JPA metamodel to reference the attributes in a type-safe way. When you execute such a CriteriaQuery, it returns a List of Tuple interface implementations. The Tuple interface provides convenient access to the selected values based on its position or its alias. In the code snippet, I defined an alias for each attribute in the query and use it to get them from the Tuple result.

Learn more:

You can not only use the Criteria API to create database queries, you can also write update and delete statements, as I show in this post: Criteria Update/Delete – The easy way to implement bulk operations with JPA2.1.

And if you want to use the Criteria API in your project, you should also have a look at the JPA metamodel. It provides a great way to create queries in a type-safe way. I explain it in detail in this post: Create type-safe queries with the JPA static metamodel.

 

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Tags

Criteria API, Query


About the author

Thorben is an independent consultant, international speaker, and trainer specialized in solving Java persistence problems with JPA and Hibernate.
He is also the author of Amazon’s bestselling book Hibernate Tips - More than 70 solutions to common Hibernate problems.

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