How Can I Convert Native Query Results to POJOs in JPA?

JPA: Converting Native Query Results to POJO

In your query, you expressed the need to convert the results of a native query into a collection of POJO classes containing five fields. You pondered whether JPA had a direct way to cast the results to a list of POJO objects.

Custom Object Mapping Using Reflection

One possible solution before the introduction of JPA 2.1 was to manually map the results using reflection. This involved defining methods to create a POJO constructor with the same number and type of fields as the native query results and mapping the tuple array returned by the query to the constructor.

Using @SqlResultSetMapping in JPA 2.1

JPA 2.1 introduced the @SqlResultSetMapping annotation, which allows you to create a mapping for the result set in an entity or an XML file. This mapping defines the target class and the columns in the result set that correspond to its properties. By using this mapping, you can create a Query object and specify the name of the mapping to cast the results directly to a list of POJO objects.

XML Mapping

If you prefer to keep annotations out of entity classes, you can define the mapping in the META-INF/orm.xml file. This involves creating a named-native-query element with a result-set-mapping attribute and defining the sql-result-set-mapping element with the constructor-result that specifies the target class and column-name mapping.

Mapped Entities (JPA 2.0)

While JPA 2.0 does not allow mapping native queries to POJO classes, it does support mapping to entities. This requires the POJO to be annotated as an entity and its properties to be mapped to the database columns.

Conclusion

The approach you choose for mapping native query results to POJO classes depends on the version of JPA you are using and your preference for annotations or XML configurations. The options presented provide various levels of flexibility and convenience, allowing you to select the one that best suits your project's needs.

The above is the detailed content of How Can I Convert Native Query Results to POJOs in JPA?. For more information, please follow other related articles on the PHP Chinese website!