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

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

In JPA (Java Persistence API), you can use SqlResultSetMapping to map the result set of a native SQL query to a POJO (Plain Old Java Object). Here's how you can do it:

  1. Define your POJO class representing the result set:
public class MyEntityDTO {
    private Long id;
    private String name;

    // Getters and setters
}
  1. Create a SqlResultSetMapping annotation to map the columns of the result set to the fields of the POJO:
import javax.persistence.Entity;
import javax.persistence.ColumnResult;
import javax.persistence.ConstructorResult;
import javax.persistence.SqlResultSetMapping;

@Entity
@SqlResultSetMapping(
    name = "MyEntityMapping",
    classes = {
        @ConstructorResult(
            targetClass = MyEntityDTO.class,
            columns = {
                @ColumnResult(name = "id", type = Long.class),
                @ColumnResult(name = "name", type = String.class)
            }
        )
    }
)
public class MyEntity {
    // Entity mapping here
}

In this example:

  • We define a SqlResultSetMapping named "MyEntityMapping".
  • We use @ConstructorResult to specify that the result set should be mapped to the constructor of the MyEntityDTO class.
  • We specify the target class (MyEntityDTO.class) and map the columns of the result set to the fields of the POJO using @ColumnResult.
  1. Use the SqlResultSetMapping in your native query:
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;
import java.util.List;

public class MyRepository {

    @PersistenceContext
    private EntityManager entityManager;

    public List<MyEntityDTO> findByCustomQuery() {
        Query query = entityManager.createNativeQuery("SELECT id, name FROM my_table", "MyEntityMapping");
        return query.getResultList();
    }
}

In this example:

  • We create a native SQL query using entityManager.createNativeQuery().
  • We specify the SQL query and the name of the SqlResultSetMapping ("MyEntityMapping") in the method.

By using SqlResultSetMapping, you can map the result set of a native SQL query to a POJO in JPA. This allows you to work with the results of the query using a more object-oriented approach.

Examples

  1. JPA NativeQuery mapping to POJO example

    Description: This query likely seeks a comprehensive example of mapping the result set of a JPA NativeQuery to a Plain Old Java Object (POJO) using SqlResultSetMapping.

    // Java code implementing mapping of NativeQuery result set to POJO using SqlResultSetMapping
@Entity
@SqlResultSetMapping(
    name = "BookResult",
    classes = @ConstructorResult(
        targetClass = Book.class,
        columns = {
            @ColumnResult(name = "id", type = Long.class),
            @ColumnResult(name = "title"),
            @ColumnResult(name = "author")
        }
    )
)
@NamedNativeQuery(
    name = "findAllBooks",
    query = "SELECT id, title, author FROM books",
    resultSetMapping = "BookResult"
)
public class Book {
    // Define fields, constructors, getters, and setters
    // that match the columns in the SELECT query
}

  2. Mapping JPA NativeQuery result to custom POJO

    Description: This query probably looks for guidance on how to customize mapping of a JPA NativeQuery result to a POJO.

    // Java code demonstrating custom mapping of NativeQuery result set to POJO
@Entity
public class CustomEntity {
    // Define fields, constructors, getters, and setters
    // as needed for your custom entity
}

// Define your SqlResultSetMapping and NamedNativeQuery
// similar to the previous example

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