Spring Data JPA difference between findBy / findAllBy

Spring Data JPA difference between findBy / findAllBy

In Spring Data JPA, both findBy and findAllBy are used to define query methods for retrieving data from a database. However, there is a subtle difference in their usage and purpose:

  1. findBy:

    • The findBy keyword is typically used to define query methods that return a single result or a collection of results based on one or more criteria.
    • You use findBy followed by the property name (or multiple property names) on which you want to filter the results. The method name specifies the criteria for the query.
    • The generated query will use the provided property names to generate the WHERE clause conditions in SQL. It's typically used for filtering and retrieving specific records based on property values.

    Example using findBy:

    // Find a user by username User findByUsername(String username);

  2. findAllBy:

    • The findAllBy keyword is used to define query methods that return a collection of results based on one or more criteria, similar to findBy.
    • However, the primary difference is that findAllBy is used when you want to retrieve multiple records that match the criteria, whereas findBy is often used when you expect a single result.
    • The generated query will use the provided property names to generate the WHERE clause conditions in SQL, just like with findBy.

    Example using findAllBy:

    // Find all users by their role List<User> findAllByRole(String role);

In summary, both findBy and findAllBy are used to create query methods for filtering data based on specific criteria. The key difference is in the expectation of the number of results: findBy is often used for single results, while findAllBy is used for multiple results. The actual method name should reflect your specific use case and the criteria you want to apply when retrieving data from the database.

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