如何在 spring 引导中映射与 JPA 的一对一关系？

Question

我已经阅读了几个关于一对一关系映射的教程，例如： https://docs.oracle.com/javaee/6/api/javax/persistence/OneToOne.html, http://websystique.com/hibernate/hibernate-one-to-one-unidirectional-with-foreign-key-associations-annotation-example/ https://en.wikibooks.org/wiki/Java_Persistence/OneToOne

我相信我遵循了这些教程，但是我的关系映射仍然没有按预期工作。我有以下类:

@Entity(name = "lesson")
public class Lesson {

    @Id
    @Type(type = "pg-uuid")
    private UUID uid;
    private String start_date_time;
    private String end_date_time;
    private String location;

    @OneToOne
    @JoinColumn(name="uid") //uid is the name of the Id i want to reference to in the subject class
    private Subject subject_uid; // subject_uid is the name of the column in my subject table

    public Lesson(UUID uid, String start_date_time, String end_date_time, String location, Subject subject_uid) {
        this.uid = uid;
        this.start_date_time = start_date_time;
        this.end_date_time = end_date_time;
        this.location = location;
        this.subject_uid = subject_uid;
    }
//getters setters

@Entity(name = "subject")
public class Subject {

    @Id
    @Type(type = "pg-uuid")
    private UUID uid;
    private String name;
    private String start_date;
    private String end_date;
    private boolean is_lesson_created;

    public Subject(UUID uid, String name, String start_date, String end_date, boolean is_lesson_created) {
        this.uid = uid;
        this.name = name;
        this.start_date = start_date;
        this.end_date = end_date;
        this.is_lesson_created = is_lesson_created;
    }

Spring Data Rest 在 /lessons 端点上创建的响应如下所示：

{
  "_embedded" : {
    "lessons" : [ {
      "start_date_time" : "2017-01-08 08:30:00",
      "end_date_time" : "2017-01-08 10:15:00",
      "location" : "A101                                                                                                ",
      "_links" : {
        "self" : {
          "href" : "http://localhost:3400/lessons/78038aeb-cdc9-4673-990e-36b8c1105500"
        },
        "lesson" : {
          "href" : "http://localhost:3400/lessons/78038aeb-cdc9-4673-990e-36b8c1105500"
        },
        "subject_uid" : {
          "href" : "http://localhost:3400/lessons/78038aeb-cdc9-4673-990e-36b8c1105500/subject_uid"
        }
      }
    } ]
  },
  "_links" : {
    "self" : {
      "href" : "http://localhost:3400/lessons{?page,size,sort}",
      "templated" : true
    },
    "profile" : {
      "href" : "http://localhost:3400/profile/lessons"
    }
  },
  "page" : {
    "size" : 20,
    "totalElements" : 1,
    "totalPages" : 1,
    "number" : 0
  }
}

当我想要访问 http://localhost:3400/lessons/78038aeb-cdc9-4673-990e-36b8c1105500/subject_uidlink 时，我得到了 404。 UUID 类型是否影响我的映射？我应该更改什么才能访问我的 student_uid？

Answer 1

终于我找到了问题所在，这是我在任何地方都没有读到的东西。当必须完成 one-to-one 连接时，JPA 提供连接的默认名称作为 table 名称下划线 id(subject_id)。就我而言，我在数据库中有一个名为 "subject" 的 table 名称，而 PK 简称为 "uid"。因此，您要做的是将 table 名称附加到要加入的属性名称：

@OneToOne
    @JoinColumn(name="subject_uid")//the pattern is: "tablename_joined attribute"
    private Subject subject_uid;

如何在 spring 引导中映射与 JPA 的一对一关系？

How to map one-to-one relationship with JPA in spring boot?

java

spring

jpa

one-to-one

spring-rest