基于其他两个实体映射相关的 JPA 实体映射

Question

不确定这是否可行，但尝试根据下面实体中的其他两个实体映射 WorkActionClass 和 WorkflowInstance 映射相关的 WorkflowInstancePlayer player。

public class Action implements Serializable {
@Id
private Long action_id;

@ManyToOne
@JoinColumn(name = "work_action_class_id", referencedColumnName = "work_action_class_id")
private WorkActionClass workActionClass;

@ManyToOne
@JoinColumn(name = "workflow_instance_id", referencedColumnName = "workflow_instance_id")
private WorkflowInstance workflowInstance;

UPDATE: How can I map to a WorkflowInstancePlayer player?????
 @ManyToOne
 @JoinColumns( {
        @JoinColumn(name = "workflow_instance_id", referencedColumnName = "workflow_instance_id", insertable = false, updatable = false),
        @JoinColumn(name = "workActionClass.role_class_id", referencedColumnName = "role_class_id", insertable = false, updatable = false)
})
 private WorkflowInstancePlayer player;

workflowInstancePlayer 是基于workflow_instance_id 和role_class_id 派生的，但role_class_id 实际上是workActionClass 映射到(workActionClass.role_class_id) 上方的属性

public class WorkflowInstancePlayer implements Serializable {
@Id
private WorkflowInstance workflowInstance;

@Id
private RoleClass roleClass;

@ManyToOne
@JoinColumn(name = "badge", referencedColumnName = "badge")
private Employee employee;

public class WorkActionClass implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "trx_seq")
private Long work_action_class_id;

@ManyToOne
@JoinColumn(name = "role_class_id")
private RoleClass roleClass;

示例数据为：

Action
------
Id = 10
work_action_class_id = 7
workflow_instance_id = 2


WorkActionClass
---------------
Id = 7
role_name = reviewer
role_class_id = 3


WorkflowInstancePlayer
----------------------
workflow_instance_id = 2
role_class_id = 3
badge = 111222

所以在 Action Entity 中，我会知道 Workflow Instance Player 是 ID 为 111222 的 Employee，而无需将徽章实际存储在 Action 表中。

更新

根据 Vlad 的帖子，我将其调整为

@ManyToOne(fetch=FetchType.LAZY)
   @JoinColumnsOrFormulas({
   @JoinColumnOrFormula(formula=@JoinFormula(value="(SELECT a.role_class_id FROM (Use Table Name not Entity Name here) a WHERE a.work_action_class_id = work_action_class_id)", referencedColumnName="role_class_id")),
   @JoinColumnOrFormula(column = @JoinColumn(name="workflow_instance_id", referencedColumnName="workflow_instance_id"))
})

Answer 1

试试这个映射：

@ManyToOne
@JoinColumn(
    name = "workflow_instance_id", 
    referencedColumnName = "workflow_instance_id",
    insertable = false, 
    updatable = false
)
private WorkflowInstance workflowInstance;

@ManyToOne
@JoinColumnOrFormula(
    formula = @JoinFormula(
            value="(SELECT a.work_action_class_id FROM WorkActionClass a WHERE a.role_class_id = role_class_id)", 
        referencedColumnName = "work_action_class_id"
    )
)
private WorkActionClass workActionClass;

@ManyToOne
@JoinColumns( {
    @JoinColumn(
        name = "workflow_instance_id", 
        referencedColumnName = "workflow_instance_id"),
    @JoinColumn(
        name = "role_class_id", 
        referencedColumnName = "role_class_id")
})
private WorkflowInstancePlayer player;