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我目前正在修补一个简单的 HTTP 资源。我的模型由带有多个“果实”的“树”组成。两者都继承自 PanacheEntity。

树：

    @Entity
    public class Tree extends PanacheEntity {
    public String name;

    @OneToMany(mappedBy = "tree", fetch = FetchType.EAGER, cascade = CascadeType.ALL, orphanRemoval = true)
    public List<Fruit> fruits = new ArrayList<>();
    }

水果

    @Entity
    public class Fruit extends PanacheEntity {

    public String name;
    public String color;
    public int cores;

    @ManyToOne
    @JsonbTransient
    public Tree tree;
    }

资源：

    import io.quarkus.hibernate.orm.rest.data.panache.PanacheEntityResource;

    public interface TreeResource extends PanacheEntityResource<Tree, Long> { }

这是我通过 Swagger 发送的 POST 请求

{
  "name": "Apple Tree",
  "fruits": [
    {
      "color": "green",
      "cores": 3,
      "name": "Apple2"
    },
    {
      "color": "red",
      "cores": 4,
      "name": "Apple"
    }
  ]
}

响应告诉我，为所有对象创建了 ID：

{
  "id": 4,
  "fruits": [
    {
      "id": 5,
      "color": "green",
      "cores": 3,
      "name": "Apple2"
    },
    {
      "id": 6,
      "color": "red",
      "cores": 4,
      "name": "Apple"
    }
  ],
  "name": "Apple Tree"
}

但是当我在 /trees 下调用 Get all 时，我得到以下响应：

[
  {
    "id": 1,
    "fruits": [],
    "name": "Oak"
  },
  {
    "id": 4,
    "fruits": [],
    "name": "Apple Tree"
  }
]

水果总是空的。检查 postgres 数据库显示 Fruit 中的所有“tree_id”列都是空的。我很确定这是一个初学者的问题，但是在检查了多个示例后，我找不到我的代码有什么问题。

4

1 回答 1

1

我有同样的问题并通过将父对象设置为子对象来解决它。我有 Job 和 JobArgs 项目要坚持。

    // ... somewhere in JobArg.java
    @JsonbTransient
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "job_id", foreignKey = @ForeignKey(name = "job_id_fk"))
    public Job job;

    @OneToMany(mappedBy = "job", cascade = CascadeType.ALL, orphanRemoval = true)
    public List<JobArg> arguments = new ArrayList<>();
    // ... somewhere in Job.java 
    // I used reactive-pgclient so my method return Uni<T>
    public void addArgument(final JobArg jobArg) {
        arguments.add(jobArg);
        jobArg.job = this;
    }
    public static Uni<Job> insert(final UUID userId, final JobDto newJob) {
        final Job job = new Job();
        //... map fields from dto ...
        newJob.getArguments().stream().map(arg -> {
            final JobArg jobArg = new JobArg();
            //... map fields from dto ...
            return jobArg;
        }).forEach(job::addArgument);
        
        final Uni<Void> jobInsert = job.persist();
        final Uni<UserAction> userActionInsert = UserAction.insertAction(type, job.id, userId, null);
        return Uni.combine().all().unis(jobInsert, userActionInsert).combinedWith(result -> job);
    }

这是来自Vlad Mihalcea 博客的示例代码：对于双向映射：

@Entity(name = "Post")
@Table(name = "post")
public class Post {
 
    @Id
    @GeneratedValue
    private Long id;
 
    private String title;
 
    @OneToMany(
        mappedBy = "post",
        cascade = CascadeType.ALL,
        orphanRemoval = true
    )
    private List<PostComment> comments = new ArrayList<>();
 
    //Constructors, getters and setters removed for brevity
 
    public void addComment(PostComment comment) {
        comments.add(comment);
        comment.setPost(this);
    }
 
    public void removeComment(PostComment comment) {
        comments.remove(comment);
        comment.setPost(null);
    }
}
 
@Entity(name = "PostComment")
@Table(name = "post_comment")
public class PostComment {
 
    @Id
    @GeneratedValue
    private Long id;
 
    private String review;
 
    @ManyToOne(fetch = FetchType.LAZY)
    private Post post;
 
    //Constructors, getters and setters removed for brevity
 
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof PostComment )) return false;
        return id != null && id.equals(((PostComment) o).getId());
    }
 
    @Override
    public int hashCode() {
        return getClass().hashCode();
    }
}

上述映射有几点需要注意：

@ManyToOne 关联使用 FetchType.LAZY，否则，我们会退回到 EAGER 获取，这对性能不利。

父实体 Post 具有两个实用方法（例如 addComment 和 removeComment），用于同步双向关联的双方。每当您使用双向关联时，您都应该始终提供这些方法，否则，您将面临非常微妙的状态传播问题。

子实体 PostComment 实现 equals 和 hashCode 方法。由于我们不能依赖自然标识符进行相等检查，因此我们需要使用实体标识符来代替 equals 方法。但是，您需要正确执行此操作，以便在所有实体状态转换中相等性一致，这也是 hashCode 必须为常量值的原因。因为我们依赖于 removeComment 的相等性，所以最好在双向关联中为子实体覆盖 equals 和 hashCode

.

于 2020-11-26T16:58:09.973 回答