将主键作为外键映射到另一个表

I have a problem regarding a foreign key relationship and its JPA counterpart.

关于外键关系及其JPA对应关系我有问题。

In the following tables. means_of_transport is a table with a consecutive numbering. The other tables have less entries with a mapping of their primary key as a foreign key to the primary key of means_of_transport. Sadly, I cannot change the data model.

在下表中。 means_of_transport是一个连续编号的表。其他表具有较少的条目，其主键作为外键的映射到means_of_transport的主键。可悲的是，我无法改变数据模型。

Table means_of_transport

表means_of_transport

CREATE TABLE means_of_transport (
    id INT PRIMARY KEY NOT NULL,
    max_capacity INT
);

Table ocean_ship

表ocean_ship

CREATE TABLE ocean_ship (
    means_of_transport_id INT PRIMARY KEY NOT NULL,
    name VARCHAR(45) NOT NULL,
    FOREIGN KEY ( means_of_transport_id ) REFERENCES means_of_transport ( id )
);
CREATE INDEX fk_ship_means_of_transport1_idx ON ocean_ship ( means_of_transport_id );

There are more tables besides ocean_ship with the same key structure but other fields.

除了ocean_ship之外，还有更多的表具有相同的键结构，但其他字段。

MeansOfTransport.java

MeansOfTransport.java

@Entity
@Table(name = "means_of_transport")
public class MeansOfTransport extends Model {
    @Id
    public Integer id;
    public Integer maxCapacity;
}

OceanShip.java

OceanShip.java

@Entity
@Table(name = "ocean_ship")
public class OceanShip extends Model {
    @Id
    @OneToOne
    @JoinColumn(table = "means_of_transport", referencedColumnName = "id")
    public MeansOfTransport meansOfTransport;

    public String name;
}

Now every time I try to use OceanShip in another JPA class as a field, I get this error: Error reading annotations for models.Classname.

现在，每当我尝试在另一个JPA类中使用OceanShip作为字段时，我都会收到此错误：读取models.Classname的注释时出错。

Am I missing some annotations?

我错过了一些注释吗？

edit

编辑

Example usage:

用法示例：

@ManyToOne
@Column(name = "ocean_ship")
public OceanShip oceanShip;

Full stack trace:

完整堆栈跟踪：

play.api.UnexpectedException: Unexpected exception[RuntimeException: Error reading annotations for models.ContainerOrder]
        at play.core.ReloadableApplication$$anonfun$get$1$$anonfun$apply$1$$anonfun$1.apply(ApplicationProvider.scala:150) ~[play_2.10.jar:2.1.5]
        at play.core.ReloadableApplication$$anonfun$get$1$$anonfun$apply$1$$anonfun$1.apply(ApplicationProvider.scala:114) ~[play_2.10.jar:2.1.5]
        at scala.Option.map(Option.scala:145) ~[scala-library.jar:na]
        at play.core.ReloadableApplication$$anonfun$get$1$$anonfun$apply$1.apply(ApplicationProvider.scala:114) ~[play_2.10.jar:2.1.5]
        at play.core.ReloadableApplication$$anonfun$get$1$$anonfun$apply$1.apply(ApplicationProvider.scala:112) ~[play_2.10.jar:2.1.5]
        at scala.util.Either$RightProjection.flatMap(Either.scala:523) ~[scala-library.jar:na]
Caused by: java.lang.RuntimeException: Error reading annotations for models.ContainerOrder
        at com.avaje.ebeaninternal.server.deploy.parse.ReadAnnotations.readAssociations(ReadAnnotations.java:54) ~[avaje-ebeanorm-server.jar:na]
        at com.avaje.ebeaninternal.server.deploy.BeanDescriptorManager.readDeployAssociations(BeanDescriptorManager.java:1034) ~[avaje-ebeanorm-server.jar:na]
        at com.avaje.ebeaninternal.server.deploy.BeanDescriptorManager.readEntityDeploymentAssociations(BeanDescriptorManager.java:565) ~[avaje-ebeanorm-server.jar:na]
        at com.avaje.ebeaninternal.server.deploy.BeanDescriptorManager.deploy(BeanDescriptorManager.java:252) ~[avaje-ebeanorm-server.jar:na]
        at com.avaje.ebeaninternal.server.core.InternalConfiguration.<init>(InternalConfiguration.java:124) ~[avaje-ebeanorm-server.jar:na]
        at com.avaje.ebeaninternal.server.core.DefaultServerFactory.createServer(DefaultServerFactory.java:210) ~[avaje-ebeanorm-server.jar:na]
Caused by: java.lang.NullPointerException: null
        at com.avaje.ebeaninternal.server.deploy.BeanTable.createJoinColumn(BeanTable.java:94) ~[avaje-ebeanorm-server.jar:na]
        at com.avaje.ebeaninternal.server.deploy.parse.AnnotationAssocOnes.readAssocOne(AnnotationAssocOnes.java:145) ~[avaje-ebeanorm-server.jar:na]
        at com.avaje.ebeaninternal.server.deploy.parse.AnnotationAssocOnes.parse(AnnotationAssocOnes.java:54) ~[avaje-ebeanorm-server.jar:na]
        at com.avaje.ebeaninternal.server.deploy.parse.ReadAnnotations.readAssociations(ReadAnnotations.java:45) ~[avaje-ebeanorm-server.jar:na]
        at com.avaje.ebeaninternal.server.deploy.BeanDescriptorManager.readDeployAssociations(BeanDescriptorManager.java:1034) ~[avaje-ebeanorm-server.jar:na]
        at com.avaje.ebeaninternal.server.deploy.BeanDescriptorManager.readEntityDeploymentAssociations(BeanDescriptorManager.java:565) ~[avaje-ebeanorm-server.jar:na]

3 个解决方案

#1

I think your DB model is conceptually not right.

我认为你的数据库模型在概念上是不对的。

It should be something like this below.

它应该是这样的。

The ocean_ship_id is the PK of the ocean_ship table. And means_of_transport_id from ocean_ship is just a FK to the "base" table means_of_transport.

ocean_ship_id是ocean_ship表的PK。来自ocean_ship的means_of_transport_id只是“基础”表means_of_transport的FK。

So I would say you get your DB model right, then worry about the JPA mapping.

所以我会说你的数据库模型正确，然后担心JPA映射。

CREATE TABLE ocean_ship (
    ocean_ship_id INT PRIMARY KEY NOT NULL,
    means_of_transport_id INT NOT NULL,
    name VARCHAR(45) NOT NULL,
    FOREIGN KEY ( means_of_transport_id ) REFERENCES means_of_transport ( id )
);

#2

The error message came up because some annotations were wrong.

出现错误消息是因为某些注释错误。

I changed the primary key of OceanShip from MeansOfTransport to Integer and have now to be careful what I enter there. That's the price I have to pay.

我将OceanShip的主键从MeansOfTransport更改为Integer，现在要小心我输入的内容。这是我必须支付的价格。

Additionally I changed the annotation where I use OceanShip from this

另外，我更改了使用OceanShip的注释

@ManyToOne
@Column(name = "ocean_ship")
public OceanShip oceanShip;

to this

对此

@ManyToOne
@JoinColumn(name = "ocean_ship", referencedColumnName = "means_of_transport_id")
public OceanShip oceanCarrierShip;

#3

See @PrimaryKeyJoinColumn and the ideas given in this thread.

请参阅@PrimaryKeyJoinColumn以及此主题中给出的想法。

Shared primary key with JPA @MapsId annotation

与JPA @MapsId注释共享主键

Might be helpful maybe?

可能有帮助吗？

#1