Hibernate：如何使用多态映射 @ManyToOne (@ManyToAny)

Question

假设我至少有两个实体。

@Entity
public class Process {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(unique = true)
    private String name;

    @ManyToAny(
            metaColumn = @Column(name = "node_type"),
            fetch = FetchType.LAZY
    )
    @AnyMetaDef(
            idType = "long", metaType = "string",
            metaValues = {
                    @MetaValue(targetEntity = Milestone.class, value = MILESTONE_DISC),
                    @MetaValue(targetEntity = Phase.class, value = PHASE_DISC)
            }
    )
    @Cascade({org.hibernate.annotations.CascadeType.ALL})
    @JoinTable(
            name = "process_nodes",
            joinColumns = @JoinColumn(name = "process_id", nullable = false),
            inverseJoinColumns = @JoinColumn(name = "node_id", nullable = false)
    )
    private Collection<ProcessNode> nodes = new ArrayList<>();

    ...
}

---

@Entity
@ToString
@DiscriminatorValue(MILESTONE_DISC)
public class Milestone implements ProcessNode {


    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    private Collection<ResultDefinition> results;

    @ManyToOne()
    private Process process;

...
}

当我尝试创建进程时，会执行以下操作：

插入里程碑（id、名称、流程）值（null、?、?）

如何映射@ManyToOne 属性，即流程不是插入里程碑表而是通过与process_nodes 表连接获得的？

---

编辑：

我现在做了以下事情：

   @ManyToOne(fetch = FetchType.LAZY)
    @Transient
    private Process process;

我可以从里程碑访问流程，但流程未保存在里程碑表中。

有没有更简洁的方法来实现这一目标？

---

第二次修改

更多细节：

ProcessNode 是其他两个实体继承自的接口。使用休眠注释@ManyToAny，我将其映射到以下结构中：

Answer 1

无论如何，这里是使用您的类的有效解决方案，它们按预期工作。

        @SpringBootApplication
    public class AccessingDataJpaApplication {
        
        public static void main(String[] args) {
            ConfigurableApplicationContext context 
                    = SpringApplication.run(AccessingDataJpaApplication.class);
            ProcessService processService 
                    = context.getBean(ProcessService.class);
    
            Process process = new Process();
            process.setName("process-1");
    
            Milestone milestoneOne = new Milestone();
            milestoneOne.setProcess(process);
            milestoneOne.setName("milestone-1");
    
            Milestone milestoneTwo = new Milestone();
            milestoneTwo.setProcess(process);
            milestoneTwo.setName("milestone-2");
    
            process.setNodes(Arrays.asList(milestoneOne, milestoneTwo));
            processService.save(process);
            processService.findAll();
        }
    }

    @Service
    @Transactional
    public class ProcessService {
    
        @Autowired
        ProcessRepository processRepository;
    
        public Process save(Process process){
            return processRepository.save(process);
        }
    
        public List<Process> findAll(){
            List<Process> processes = processRepository.findAll();
            processes.forEach(System.out::println);
            
           //This prints the following
    
            // Process{id=1, name='process-1',
            // nodes=[Milestone{id=1, name='milestone-1'},
            //        Milestone{id=2, name='milestone-2'}]}

            return processes;
        }
    }

更新

根据下面的 cmets，问题是 process_id 列在 process_nodes 连接表和 milestone 表中重复。我希望利用以下内容来避免milestone 表中的process_id 列，如下所示，但这也不起作用

     @ManyToOne
     @JoinTable(
            name = "process_nodes",
            joinColumns = @JoinColumn(name = "process_id", 
                                      nullable = false, 
                                      insertable = false, 
                                      updatable = false),
            inverseJoinColumns = @JoinColumn(name = "node_id", 
                                           nullable = false, 
                                          insertable = false, 
                                          updatable = false)
    )
    @WhereJoinTable(clause = "node_type='milestone'")
    private Process process;