无法在 Spring 数据中实例化 DTO 投影

Question

I am trying to return a custom object RecordData from my repository class, but it tries to instantiate my main Record class. I've tried using Interface Projections , but the result is the same.

import org.springframework.data.cassandra.core.mapping.PrimaryKey;
import org.springframework.data.cassandra.core.mapping.Table;

@Table
public class Record {

    public record RecordData(long created_at, double value) {

    }

    @PrimaryKey
    private final long sensor_id;

    private final long created_at;

    private final double value;

    public Record(long sensor_id, long created_at, double value) {
        this.sensor_id = sensor_id;
        this.created_at = created_at;
        this.value = value;
    }

    public long getSensorId() {
        return sensor_id;
    }

    public long getCreatedAt() {
        return created_at;
    }

    public double getValue() {
        return value;
    }

}

@Repository
public interface RecordsRepository extends CassandraRepository<Record, String> {

    @Query("SELECT created_at, value FROM record WHERE sensor_id = ?0 and created_at > ?1")
    List<Record.RecordData> findBySensorIdAndCreatedAt(Long sensorId, Long createdAt);

}

Stack-trace:

org.springframework.data.mapping.model.MappingInstantiationException: Failed to instantiate com.example.mainservice.models.entities.Record using constructor public com.example.mainservice.models.entities.Record(long,long,double) with arguments null,300,0.0

Caused by: java.lang.IllegalArgumentException: Parameter sensor_id must not be null!

Answer 1

Make these changes in your code:

    @Entity
    public class Record {

    public record RecordData(long created_at, double value) {

    }

    @Id
    private final long sensor_id;

    private final long created_at;

    private final double value;

    public Record(long sensor_id, long created_at, double value) {
        this.sensor_id = sensor_id;
        this.created_at = created_at;
        this.value = value;
    }

    public long getSensorId() {
        return sensor_id;
    }

    public long getCreatedAt() {
        return created_at;
    }

    public double getValue() {
        return value;
    }

}

And

@Repository
public interface RecordsRepository extends CassandraRepository<Record, String> {

    @Query("SELECT r.created_at, r.value FROM Record r WHERE r.sensorId = :sensorId and r.createdAt > :createdAt")
    List<Record.RecordData> findBySensorIdAndCreatedAt(@Param("sensorId") Long sensorId, @Param("createdAt") Long createdAt);

}

Answer 2

Try making your table an entity so that it retrieves the data and map it with your object.

As a class which should be persisted in a database it must be annotated Use javax.persistence library for imports

User @Id as this will make your id a primary key as per JPA

Add the @Entity annotation in your table like below and there is no need to write @Table if you are not giving a custom name to your table as @Table is used to name your table. It is stored as that name in your database

@Entity  //insert here
public class Record {

public record RecordData(long created_at, double value) {

}

@Id
private final long sensor_id;
....
}

Try this it should work

Answer 3

you can try this

@Entity
@Table(name="record")
public class Record {

    public record RecordData(long created_at, double value) {

    }

    @Id
    private final long sensor_id;

    private final long created_at;

    private final double value;

    public Record(long sensor_id, long created_at, double value) {
        this.sensor_id = sensor_id;
        this.created_at = created_at;
        this.value = value;
    }

    public long getSensorId() {
        return sensor_id;
    }

    public long getCreatedAt() {
        return created_at;
    }

    public double getValue() {
        return value;
    }

}

@Repository
public interface RecordsRepository extends CassandraRepository<Record, String> {

    @Query("SELECT created_at, value FROM record WHERE sensor_id = :sensor_id and created_at > :created_at")
    List<Record.RecordData> findBySensorIdAndCreatedAt(@Param("sensor_id")Long sensorId,@Param("created_at") Long createdAt);

}

Answer 4

I should think having a separate class would help

public class RecordData {
    private Long createdAt;
    private Double value;
    public RecordData(Long createdAt, Double value) {
        this.createdAt = createdAt;
        this.value = value;
    }
}

@Repository
public interface RecordsRepository extends CassandraRepository<Record, String> {

    @Query("SELECT new RecordData(r.created_at, r.value) FROM Record r WHERE r.sensorId = :sensorId and r.createdAt > :createdAt")
    List<RecordData> findBySensorIdAndCreatedAt(@Param("sensorId") Long sensorId, @Param("createdAt") Long createdAt);
}

Answer 5

All I needed to add was an empty argument constructor.

public Record() {
}