带有命名列的Spring data JPA@Query映射

Question

public interface VehicleRepository extends JpaRepository<Vehicle, String> {
    @Query("select v.sourceModule as sourceModule, count(v) as vehicleCount from Vehicle v group by v.sourceModule")
    List<Object[]> sourceModuleStats();
}

@Override
public List<SourceModuleStatDTO> getSourceModuleStats() {
    List<Object[]> objects = vehicleRepository.sourceModuleStats();

    return objects.stream()
            .map(o->SourceModuleStatDTO.from((String)o[0], (Long)o[1]))
            .collect(Collectors.toList());
}

@Value.Immutable
@JsonSerialize(as = ImmutableSourceModuleStatDTO.class)
@JsonDeserialize(as = ImmutableSourceModuleStatDTO.class)
public abstract class SourceModuleStatDTO {
    public abstract String sourceModule();
    public abstract long vehicleCount();

    public static SourceModuleStatDTO from(String sm, long c) {
        return ImmutableSourceModuleStatDTO.builder()
                .sourceModule(sm)
                .vehicleCount(c)
                .build();
    }
}

这里的问题是映射，我需要强制转换结果或手动检查一切。即使jdbctemplate有更好的映射能力，我也不敢相信没有更好的方法来做到这一点。

我也试过这样做:https://stackoverflow.com/a/36329166/840315，但您需要将类路径硬编码到查询中以使其工作，而且我仍然需要将对象映射到不可变的对象。

使用JdbcTemplate，您可以使用行映射器(src):

private static final class EmployeeMapper implements RowMapper<Employee> {
    @Override
    public Employee mapRow(ResultSet rs, int rowNum) throws SQLException {
        Employee employee = new Employee();
        employee.setCountry(rs.getString("country"));
        employee.setEmployeeName(rs.getString("employee"));
        return employee;
    }
}

spring data JPA@query是否有类似的内容？

Answer 1

用下面的预测怎么样？

static interface VehicleStats { 
    public String getSourceModule();
    public Long getVehicleCount();
}

您的存储库方法将是

@Query("select v.sourceModule as sourceModule, count(v) as vehicleCount from Vehicle v group by v.sourceModule")
List<VehicleStats> sourceModuleStats();

在您的服务类中，您可以使用如下所示的接口方法。

List<VehicleStats> objects = vehicleRepository.sourceModuleStats();
return objects.stream()
        .map(o->SourceModuleStatDTO.from(getSourceModule(),getVehicleCount() )
        .collect(Collectors.toList());