How to combine two DAOs in generic way with only one method in Service layer in Spring Boot - spring

Question

Is it possible to combine two DAOs into one Service method?
I want to create a generic method which will choose correct DAO based on the input parameter. What for now I came up with is the method which will accept Dao from the outside the service object. But this requires to initialize appropriate Dao in the Controller which is a little bit ugly...
Measurement is just an interface for Temperature.java and Humidity.java entities with separate tables on PostgreSQL.
#Service
public class MeasurementService {
#Autowired
private TemperatureDao temperatureDao;
#Autowired
private HumidityDao humidityDao;
public<T extends PagingAndSortingRepository<Measurement, Long>> void insertMeasurementForUser(String username, List<Measurement> measurements, T dao) {
dao.saveAll(measurements);
}
}
TemperatureDao.java
#Repository
public interface TemperatureDao extends PagingAndSortingRepository<Temperature, Long> {
#Query("select u from Temperature u where u.owner = ?1 order by u.id desc")
List<Temperature> findLatestTemperatureForUser(User user, Pageable pageable);
}
HumidityDao.java
#Repository
public interface HumidityDao extends PagingAndSortingRepository<Humidity, Long> {
#Query("select u from Humidity u where u.owner = ?1 order by u.id desc")
List<Humidity> findLatestHumidityForUser(User user, Pageable pageable);
}
Temperature.java
#Entity
#Table(name = "temperature")
public class Temperature implements Measurement {
#Id
#Column(name = "id")
#GeneratedValue(strategy = GenerationType.SEQUENCE)
private Long id;
#Column(name = "th1value")
private Float th1Value;
#Column(name = "timestamp")
#NotNull
private LocalDateTime timestamp;
#ManyToOne
#JoinColumn(name = "user_id")
#NotNull
private User owner;
public Temperature() {
}
public Temperature(Float th1Value, LocalDateTime timestamp, User owner) {
this.th1Value = th1Value;
this.timestamp = timestamp;
this.owner = owner;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
#JsonDeserialize(using = LocalDateTimeDeserializer.class)
public LocalDateTime getTimestamp() {
return timestamp;
}
#JsonSerialize(using = LocalDateTimeSerializer.class)
public void setTimestamp(LocalDateTime timestamp) {
this.timestamp = timestamp;
}
#Override
public User getOwner() {
return owner;
}
#Override
public void setOwner(User owner) {
this.owner = owner;
}
}
Humidity.java
#Entity
#Table(name = "humidity")
public class Humidity {
#Id
#Column(name = "id")
#GeneratedValue(strategy = GenerationType.SEQUENCE)
private Long id;
#Column(name = "hum1value")
private Float hum1Value;
#Column(name = "timestamp")
#NotNull
private LocalDateTime timestamp;
#ManyToOne
#JoinColumn(name = "user_id")
#NotNull
private User owner;
public Humidity() {
}
public Humidity(Float hum1Value, LocalDateTime timestamp, User owner) {
this.hum1Value = hum1Value;
this.timestamp = timestamp;
this.owner = owner;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
#JsonDeserialize(using = LocalDateTimeDeserializer.class)
public LocalDateTime getTimestamp() {
return timestamp;
}
#JsonSerialize(using = LocalDateTimeSerializer.class)
public void setTimestamp(LocalDateTime timestamp) {
this.timestamp = timestamp;
}
public User getOwner() {
return owner;
}
public void setOwner(User owner) {
this.owner = owner;
}
}
Any ideas?

Answer 1

You could write a Resolver pattern to return needed dao based on your conditions. You service will use the resolver to get the correct dao.
public HellDao implements BaseDao {
public void save();
}
public ByeDao implements BaseDao {
public void save();
}
public DaoResolver {
#Autowired
private helloDao;
#Autowired
private byeDao;
public BaseDao resolve(Object input) {
//based on input return the correct dao
BaseDao resolvedDao = null;
switch(input.enum) {
case Hello:
resolvedDao = helloDao;
break;
case Hello:
resolvedDao = byeDao;
break;
default:
//decide something for default
}
return resolvedDao;
}
}
public class MyService {
#Autowired
private DaoResolver daoResolver;
public Object doSomething() {
BaseDao dao = daoResolver.resolve(someObject);
//you will get HelloDao or ByeDao based on the input
dao.save();
}
}

Answer 2

You can check for the type of measurements using instanceof so you could do it without generics.
public void insertMeasurementForUser(String username, List<Measurement> measurements) {
if(measurements.get(0) instanceof Temperature)
temperatureDao.saveAll(measurements);
else if(measurements.get(0) instanceof Humidity)
humidityDao.saveAll(measurements);
}