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Discover how to prevent Hibernate from creating tables for entity classes while using JPA with native queries! Learn about DTOs, custom result mappings, and more.
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This video is based on the question https://stackoverflow.com/q/62925203/ asked by the user 'Hugo Feijó' ( https://stackoverflow.com/u/11951761/ ) and on the answer https://stackoverflow.com/a/62953357/ provided by the user 'Hugo Feijó' ( https://stackoverflow.com/u/11951761/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Stop Hibernate’s Automatic Table Creation for Entity Classes

In the world of Java development, particularly when we integrate frameworks like Hibernate and JPA, developers often encounter the challenge of automatic table creation. If you're using Hibernate to map a domain class, the framework tends to create a corresponding database table for each entity class by default. This might not be desirable, especially when you're generating reports or working with complex queries without needing separate tables for each entity. If you’ve faced this issue, you’re not alone. In this post, we’ll dive deep into how to manage this behavior efficiently.

Understanding the Problem

When you define a class with the @ Entity annotation in Hibernate, the expectation is that it will represent a table in your database. However, there are scenarios—like creating reports from multiple tables—where we may not want Hibernate to create unnecessary tables for every entity. This can lead to a cluttered database schema and complicate maintenance, especially with multiple domain classes.

The Sample Domain Class

Here's a quick overview of a sample domain class that illustrates the default behavior of Hibernate:

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As you can see, the usage of @ Entity prompts Hibernate to create a corresponding table, which we wish to avoid.

Proposed Solution

Transition to a Data Transfer Object (DTO)

To efficiently handle this issue, one recommended approach is to use a Data Transfer Object (DTO) instead of an entity class for your reports. A DTO is a simple object that is used to encapsulate data, meaning it can carry data between processes. Here's how we modify our domain class:

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With this change, we've removed the @ Entity annotation, which will prevent Hibernate from creating a new table in the database.

Implement Custom Result Mapping

To enable JPA to map the results from SQL queries to our DTO, we need to implement custom result mapping using the @ SqlResultSetMapping annotation. This must be done in a class annotated with @ Entity, but to keep things organized, we can create a dedicated configuration class for mapping purposes:

[[See Video to Reveal this Text or Code Snippet]]

Create a Custom Repository Implementation

Lastly, we can create a custom implementation of the JPA repository to manage the database queries while leveraging our DTO:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By transitioning to a DTO and implementing a custom result mapping, you can effectively control Hibernate's behavior of automatically generating tables for each entity class. This approach allows for cleaner code and a more manageable database schema, especially when working with complex reporting systems.

Final Thoughts

If you have any better or alternative solutions, feel free to share! Your input can help the community tackle similar challenges more effectively. Thank you for reading, and happy coding!