How to map the result set of a JPA NativeQuery to a POJO using SqlResultSetMapping

How to map the result set of a JPA NativeQuery to a POJO using SqlResultSetMapping

In JPA (Java Persistence API), you can map the result set of a native SQL query to a POJO (Plain Old Java Object) using SqlResultSetMapping. SqlResultSetMapping is used to specify how the columns from the result set should be mapped to fields in your custom POJO class. Here's how you can do it:

  1. Create Your POJO Class: First, create a POJO class that matches the structure of the result set. Make sure to define fields with the same names and types as the columns you want to map.

    public class MyCustomEntity {
    private Long id;
    private String name;
    
    // Getters and setters
}

  2. Define SqlResultSetMapping: In your JPA entity class (or any other class in your persistence unit), define the SqlResultSetMapping. You can do this with the @SqlResultSetMapping annotation. This annotation specifies the name of the mapping and how the columns should be mapped to fields in your POJO.

    import javax.persistence.*;

@SqlResultSetMapping(
    name = "MyCustomEntityMapping",
    classes = {
        @ConstructorResult(
            targetClass = MyCustomEntity.class,
            columns = {
                @ColumnResult(name = "id", type = Long.class),
                @ColumnResult(name = "name", type = String.class)
            }
        )
    }
)

    In this example:

    • name specifies the name of the mapping.
    • classes specifies an array of ConstructorResult annotations. Each ConstructorResult annotation maps the result set columns to constructor parameters of your POJO.

  3. Create the Native SQL Query: Now, you can create a native SQL query using the createNativeQuery method of the EntityManager. Specify the SQL query and use the SqlResultSetMapping name you defined.

    String sql = "SELECT id, name FROM my_table";
Query query = entityManager.createNativeQuery(sql, "MyCustomEntityMapping");

  4. Execute the Query and Retrieve Results: Finally, execute the query and retrieve the results. The query result will be a list of your custom POJOs.

    List<MyCustomEntity> results = query.getResultList();

That's it! You've successfully mapped the result set of a native SQL query to a custom POJO using SqlResultSetMapping. Make sure that the column names in your SQL query match the names specified in the @ColumnResult annotations within the SqlResultSetMapping.

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