带有命名列的 Spring 数据 JPA @Query 映射 [英] Spring data JPA @Query mapping with named columns

问题描述

我在 MySQL 中使用 Spring Boot 1.5 和 Spring Data JPA.我试图在单个表上运行一个简单的计数查询，但找不到比这更好的方法来映射查询结果.:

I use Spring Boot 1.5 and spring data JPA with MySQL. I tried to run a simple counting query on a single table, but could not find a better way to map the Query results than this.:

存储库:

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();
}

服务:

@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());
}

我使用 org.immutables，所以 DTO.:

I use org.immutables, so the DTO.:

@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，我需要转换结果或手动检查所有内容.即使 JdbcTemplate 具有更好的映射能力，我也不敢相信没有更好的方法可以做到这一点.

The problem here is the mapping, I need to cast the results or manually check everything. Even JdbcTemplate has better mapping capabilities, I can't believe there is no better way to do this.

我也试过这个:https://stackoverflow.com/a/36329166/840315，但你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对象.

I tried this too: https://stackoverflow.com/a/36329166/840315 , but you need to hard code classpaths into the Query to get it work and also I would still need to map the objects to Immutables.

使用 JdbcTemplate，您可以使用 RowMapper (src) :

Using JdbcTemplate, you can use the RowMapper (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 数据 JPA @Query 是否有类似的东西?

Is there something similar for spring data JPA @Query?

推荐答案

如何使用 投影如下?

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

你的存储库方法是

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

在您的 Service 类中，您可以使用如下接口方法.

In your Service class, you can use the interface methods as below.

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

这篇关于带有命名列的 Spring 数据 JPA @Query 映射的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！