Question

我正在尝试将用户列表映射到位置对象，但我得到了映射异常。这是因为数据库无法识别List对象？或者为什么我会得到这个例外？

这是我的用户类：

@Entity
@Table(name = "users")
public class NewUser extends BaseEntity{
    private String login;
    private String fullName;

    private Location location;
    private Department department;
    private Role role;
    private Long days;
    private String team;
    private Long managerId;
    private String hiredDate;

    public String getLogin() {
        return login;
    }

    public void setLogin(String login) {
        this.login = login;
    }

    public String getFullName() {
        return fullName;
    }

    public void setFullName(String fullName) {
        this.fullName = fullName;
    }

    public Location getLocation() {
        return location;
    }

    @ManyToOne(targetEntity = Location.class)
    @JoinTable(name = "location")
    public void setLocation(Location location) {
        this.location = location;
    }

    public Department getDepartment() {
        return department;
    }

    @ManyToOne(targetEntity = Department.class)
    public void setDepartment(Department department) {
        this.department = department;
    }

    public Role getRole() {
        return role;
    }

    @ManyToOne(targetEntity = Role.class)
    @JoinTable(name = "role")
    public void setRole(Role role) {
        this.role = role;
    }

位置等级：

@Entity
@Table(name = "location")
public class Location extends BaseEntity{
    private List<NewUser> users;

    public List<NewUser> getUsers() {
        return users;
    }

    @OneToMany(targetEntity = NewUser.class, mappedBy = "location")
    @JoinTable(name = "users")
    public void setUsers(List<NewUser> users) {
        this.users = users;
    }
}

基础实体：

@MappedSuperclass
public abstract class BaseEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }
}

错误是：

Caused by: org.hibernate.MappingException: Could not determine type for: java.util.List, at table: location, for columns: [org.hibernate.mapping.Column(users)]

如何使用hibernate注释有效地进行关系映射？

Answer 1

您的映射不正确。假设您希望用户表中的FK指向相应的位置，请使用以下内容：

在用户

中

@ManyToOne
@JoinColumn(name = "location_id")
public void setLocation(Location location) {
    this.location = location;
}

在位置

@OneToMany(mappedBy = "location")
public void setUsers(List<NewUser> users) {
    this.users = users;
}

如果您不希望在users表中将外键设置为Location，那么您可以使用连接表'user_locations'，其中列为user_id（FK为用户）和location_id（FK为位置），并使用@JoinTable注释以相应地指定它。在你的映射中，这看起来像：

@ManyToOne
@JoinTable(name = "user_locations", joinColumns = @JoinColumn(name="user_id"), inverseJoinColumns = @JoinColumn(name = "location_id"))
public void setLocation(Location location) {
    this.location = location;
}

Answer 2

Hibernate已经知道每个实体的表格，因为您使用@Table注释来指定它。你建立了两个独立的关系，而不是一个双方关系。

使用mappedBy，声明您想要依赖的其他权利字段：

<强> Location.java

@OneToMany(fetch=FetchType.LAZY, cascade = {CascadeType.ALL}, mappedBy="location")
public List<NewUser> getUsers() {
    return users;
}

<强> NewUser.java

@ManyToOne(fetch=FetchType.LAZY)
@JoinColumn(name="id_user")
public Location getLocation() {
    return location;
}

另见：

如何在春天将对象列表映射到具有休眠的表中？

2 个答案: