我正在尝试编写与以下SQL查询等效的Hibernate Criteria API:
select c.NAME as carName,
cc.COLOR_CODE as colorCode,
cc.COLOR as color,
c.DESCRIPTION as desc,
c.MANUFACTURE_YEAR as year
from CAR c
LEFT JOIN CAR_COLOR CC on c.COLOR_CODE_ID = CC.ID
WHERE CC.COLOR_CODE = ?
这是我的Car
实体
public class Car extends BaseEntity {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String name;
@Basic
@Column(name = "MANUFACTURE_YEAR")
private String year;
@Basic
@Column(name = "DESCRIPTION")
private String desc;
private Long colorCodeId;
private String manufacturer;
}
这是我的CarColor
实体
public class CarColor extends BaseEntity {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String color;
private String colorCode;
}
Car.colorCodeId
是引用CarColor.id
的外键。尽管没有明显的实体级关系,但我无法添加任何关系。
我想在这两个表/实体之间进行左连接并将结果映射到CarSearch
?我该怎么做?非常感激。
public class CarSearch {
private String carName;
private String colorCode;
private String color;
private String desc;
private String year;
}
答案 0 :(得分:1)
可以使用笛卡尔积
CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery<Object[]> query = cb.createQuery(Object[].class);
Root<Car> car = query.from(Car.class);
Root<CarColor> carColor = query.from(CarColor.class);
Predicate joinPredicate = cb.equal(car.get("colorCodeId"), carColor.get("id"));
query.multiselect(
car.get("name"),
carColor.get("colorCode"),
carColor.get("color"),
car.get("desc"),
car.get("year")
).where(
joinPredicate,
cb.equal(carColor.get("colorCode"), "yourColorCode")
);
为避免在查询结果中出现Object[]
,应使用适当的构造函数创建QueryResultDto
类,并使用这种方式
CriteriaQuery<QueryResultDto> query = cb.createQuery(QueryResultDto.class);
//...
query.select(cb.construct(QueryResultDto.class,
car.get("name"),
carColor.get("colorCode"),
carColor.get("color"),
car.get("desc"),
car.get("year")
));