Hibernate HQL带select子句查询报InvalidPathException问题求助

刚接触Hibernate与HQL，现有Employee、Person、House三个实体类，尝试执行HQL语句：
select person from Employee where house.id=:houseId
以获取指定houseId对应的Person对象，但触发了InvalidPathException和QuerySyntaxException；而去掉select子句的语句from Employee where house.id=:houseId可正常运行。仅需获取Person对象，请问问题出在哪里？

Employee实体类 #

public class Employee implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @Column
    private Integer authority;

    @Column
    private String username;

    @Column(name = "user_password")
    private String password;

    @Column
    private String title;

    @OneToOne
    @JoinColumn(name = "person_id", referencedColumnName = "id")
    private Person person;

    @Column
    private Integer gender;

    @Column
    private String ssn;

    @Column(name = "car_info")
    private String carInfo;

    @Column(name = "birth_date")
    private Date birthDate; //java.util Date vs java.sql.Date?

    @OneToOne
    @JoinColumn(name = "visa_status_id", referencedColumnName = "id")
    private VisaStatus visaStatus;

    @Column(name = "license_number")
    private Integer licenseNumber;

    @Column(name = "license_expiration_date")
    private Date licenseExpirationDate;

    @ManyToOne
    @JoinColumn(name = "housing_id", referencedColumnName = "id")
    private House house;
}

Person实体类 #

public class Person implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @Column(name = "first_name")
    private String firstName;

    @Column(name = "last_name")
    private String lastName;

    @Column(name = "middle_name")
    private String middleName;

    @Column(name = "preferred_name")
    private String preferredName;

    @ManyToOne
    @JoinColumn(name = "address_id", referencedColumnName = "id")
    private Address address;

    @Column
    private String email;

    @Column(name = "ceil_phone")
    private String ceilPhone;

    @Column(name = "work_phone")
    private String workPhone;

}

House实体类 #

public class House implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @OneToOne
    @JoinColumn(name = "address_id",  referencedColumnName = "id")
    private Address address;

    @ManyToOne
    @JoinColumn(name = "contact_id")
    private Contact contactHR;

    @ManyToOne
    @JoinColumn(name = "landlord_id")
    private Person landlord;
}

报错信息 #

org.hibernate.hql.internal.ast.InvalidPathException: Invalid path: 'house.id'
org.hibernate.hql.internal.ast.QuerySyntaxException: Invalid path: 'house.id' [select person from example.project.domain.entity.Employee where house.id=:houseId]

问题根源 #

当你写select person from Employee where house.id=:houseId时，Hibernate会把查询结果的根对象切换成Person，后续的house.id会被解析成Person的属性，但Person里根本没有house这个关联，自然就报路径无效的错误。而不带select的语句from Employee where house.id=:houseId是以Employee为根对象，house是Employee的属性，所以能正常识别。

解决办法 #

最直接的方式是给Employee起别名，明确指定house是Employee的属性，让Hibernate正确解析路径：

select e.person from Employee e where e.house.id=:houseId

如果后续需要更灵活的关联查询，也可以给Person加上反向关联（在Person类里添加@OneToOne(mappedBy = "person") private Employee employee;），然后用关联查询的方式：

select p from Person p join p.employee e where e.house.id=:houseId

不过第一种办法不需要修改实体类，更适合当前场景。

内容的提问来源于stack exchange，提问作者CitoC