Tipp and tricks using Spring Data

Spring Data is a very comfortable way of defining DAO objects for your project. It can generate a DAO for your entity class, and provide all basic CRUD functions out of the box. You only need to define an interface, inherited from CrudRepository.

For more information of Spring Data basics I recommend reading following resources

• http://projects.spring.io/spring-data
• https://www.petrikainulainen.net/spring-data-jpa-tutorial/

It is however not always enough to use the basic functionality of Spring Data. I collect here some more interesting examples of using the possibilities of the framework.

Searching for String with prefix using Query

@Transactional
@Repository
public interface PushServiceConfigurationDao extends CrudRepository<PushSecrviceConfiguration, String> {

@Query(value = "SELECT c.value FROM PushSecrviceConfiguration c where c.key = UPPER(CONCAT('GOOGLE_GCM_API_KEY_', :appName))")
public String findGmcAuthKeyByAppName(@Param("appName") String appName);

}

Get record count

@Query(value = "SELECT COUNT(l) FROM Logic l where l.enabled = true AND l.gateway.id = :gatewayId")
int numberOfEnabledLogicsByGatewayId(@Param("gatewayId") String gatewayId);

Using enum as search parameter

@Query(value = "SELECT t FROM Logic t where t.gateway.id = :gatewayId and t.logicType = :logicType")
List<Logic> findAllByGatewayIdAndLogicType(@Param("gatewayId") String gatewayId, @Param("logicType") LogicType logicType);

Using @EntityGraph to control eager loading of elements

Defining the entitygraph in your domain class

@NamedEntityGraphs({
 @NamedEntityGraph(name = "graph.gateway.authTokens", attributeNodes = @NamedAttributeNode("authTokens")),
 @NamedEntityGraph(name = "graph.gateway.devices", attributeNodes = @NamedAttributeNode("devices"))
})
public class Gateway implements java.io.Serializable { ...

Using @EntityGraph annotation in your query

@EntityGraph(value = "graph.gateway.authTokens", type = EntityGraphType.LOAD)
Gateway findByDeviceCode(String deviceCode);

Defining native update command

@Modifying
@Query(value = "UPDATE ws_message_queue SET processor_id = ?2 WHERE backend_ip = ?1 AND processor_id is null", nativeQuery = true)
int reserveMessagesForProcessing(String backendIp, String processorId);