Java 将外键连接到中间实体

我的数据库中有4个表用户（角色id列作为外键）、角色、权限和名为角色权限的中间表（角色和权限之间的关系为M:N）

我想根据特定用户的角色id获取其所有权限

中间表的定义如下：

CREATE TABLE role_permission
(
    role_id TINYINT NOT NULL,
    perm_id TINYINT NOT NULL,
    CONSTRAINT role_permission_pk PRIMARY KEY (role_id, perm_id),
    CONSTRAINT role_permission_f1 FOREIGN KEY (role_id) REFERENCES role (rid),
    CONSTRAINT role_permission_f2 FOREIGN KEY (perm_id) REFERENCES permission (pid)
);

@Entity
@Table(name = "role_permission")
public class RolePermission {
    @EmbeddedId
    private RolePermissionPK id;
    @ManyToOne
    @JoinColumn(name = "role_id", referencedColumnName = "rid", insertable = false, updatable = false)
    private Role role;
    @ManyToOne
    @JoinColumn(name = "perm_id", referencedColumnName = "pid", insertable = false, updatable = false)
    private Permission permission;
...
}

@ManyToMany
@JoinTable(
        name = "role_permission",
        joinColumns = @JoinColumn(name = "role_id"),
        inverseJoinColumns = @JoinColumn(name = "perm_id")
)
List<Permission> permissions;

与此表相关的实体如下所示：

CREATE TABLE role_permission
(
    role_id TINYINT NOT NULL,
    perm_id TINYINT NOT NULL,
    CONSTRAINT role_permission_pk PRIMARY KEY (role_id, perm_id),
    CONSTRAINT role_permission_f1 FOREIGN KEY (role_id) REFERENCES role (rid),
    CONSTRAINT role_permission_f2 FOREIGN KEY (perm_id) REFERENCES permission (pid)
);

@Entity
@Table(name = "role_permission")
public class RolePermission {
    @EmbeddedId
    private RolePermissionPK id;
    @ManyToOne
    @JoinColumn(name = "role_id", referencedColumnName = "rid", insertable = false, updatable = false)
    private Role role;
    @ManyToOne
    @JoinColumn(name = "perm_id", referencedColumnName = "pid", insertable = false, updatable = false)
    private Permission permission;
...
}

@ManyToMany
@JoinTable(
        name = "role_permission",
        joinColumns = @JoinColumn(name = "role_id"),
        inverseJoinColumns = @JoinColumn(name = "perm_id")
)
List<Permission> permissions;

但是当我试图在我的User类中获取此字段时，它不会返回任何结果：

@OneToMany(mappedBy = "role")
private List<RolePermission> permissions;

@OneToMany（mappedBy=“role”）
私有列表权限；

---

数据库工作正常，包括角色、权限和角色权限在内的所有实体也工作正常。但是我无法找出RolePermission类和User类之间缺少的链接。

角色表和权限表之间的M:N连接应该在角色表中定义，如下所示：

CREATE TABLE role_permission
(
    role_id TINYINT NOT NULL,
    perm_id TINYINT NOT NULL,
    CONSTRAINT role_permission_pk PRIMARY KEY (role_id, perm_id),
    CONSTRAINT role_permission_f1 FOREIGN KEY (role_id) REFERENCES role (rid),
    CONSTRAINT role_permission_f2 FOREIGN KEY (perm_id) REFERENCES permission (pid)
);

@Entity
@Table(name = "role_permission")
public class RolePermission {
    @EmbeddedId
    private RolePermissionPK id;
    @ManyToOne
    @JoinColumn(name = "role_id", referencedColumnName = "rid", insertable = false, updatable = false)
    private Role role;
    @ManyToOne
    @JoinColumn(name = "perm_id", referencedColumnName = "pid", insertable = false, updatable = false)
    private Permission permission;
...
}

@ManyToMany
@JoinTable(
        name = "role_permission",
        joinColumns = @JoinColumn(name = "role_id"),
        inverseJoinColumns = @JoinColumn(name = "perm_id")
)
List<Permission> permissions;

---

您说用户有一个role\u id列，用于标识其角色。所以用户应该有一个manytone和Role：用户有一个Role。RolePermission实体也没用：您可以在角色和权限之间有很多关联。您定义的关联毫无意义：用户没有角色权限。它有一个角色，该角色有权限。数据库已设计好，无法更改。“角色”数据库包含所有实现的用户角色，“权限”表包含所有权限。中间表“RolePermission”为每个实现的角色提供权限。因此，为了获得该用户的给定权限，我必须从“RolePermission”表中检索数据。数据库不是问题所在。问题在于您的Java代码。再读一遍我的评论。我从未建议对你的数据库做任何更改。