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问当父实体和子实体中存在同名属性时，“mappedBy引用未知的目标实体属性”
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Stack Overflow用户

提问于 2020-10-14 05:29:25

回答 2查看 674关注 0票数 0

我使用的是SpringBootV1.5.3，当我使用Hibernate继承时，当父实体和子实体中都有同名的属性时，就会发生AnnotationException: mappedBy reference an unknown target entity property。

例如：

Apple => RedApple
      => GreenApple
      => etc.
Tree  => RedAppleTree
      => GreenAppleTree
      => etc.

// Tree.java

@Entity
@Data
@NoArgsConstructor
@AllArgsConstructor(access = AccessLevel.PRIVATE)
@EqualsAndHashCode(exclude = {"apples"})
@DiscriminatorColumn(name = "colour")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public abstract class Tree {
    @Id
    @GeneratedValue
    private Long id;
}

// RedAppleTree.java

@Entity
@Table(name = "tree")
@DiscriminatorValue("RED")
public class RedAppleTree extends Tree {
    @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true, mappedBy = "tree")
    private List<RedApple> apples;
}

// Apple.java

@Entity
@Data
@NoArgsConstructor
@AllArgsConstructor(access = AccessLevel.PRIVATE)
@DiscriminatorColumn(name = "colour")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public abstract class Apple {
    @Id
    @GeneratedValue
    private Long id;

    @Enumerated(EnumType.STRING)
    @Column(insertable = false, updatable = false)
    private Colour colour;

    @JoinColumn(insertable = false, updatable = false)
    @ManyToOne
    private Tree tree;
}

// RedApple.java

@Entity
@Table(name = "apple")
@DiscriminatorValue("RED")
public class RedApple extends Apple {
    @JoinColumn(insertable = false, updatable = false)
    @ManyToOne
    private RedAppleTree tree;
}

// Colour.java

public enum Colour {
    RED,
    GREEN,
}

Apple.tree和RedApple.tree同时存在。在父Apple中，类型是Tree；在子RedApple中，类型是RedAppleTree。

现在，当项目运行时，我得到：

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaAutoConfiguration.class]: Invocation of init method failed; nested exception is org.hibernate.AnnotationException: mappedBy reference an unknown target entity property: com.example.demo.dao.RedApple.tree in com.example.demo.dao.RedAppleTree.apples
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean (AbstractAutowireCapableBeanFactory.java:1628)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean (AbstractAutowireCapableBeanFactory.java:555)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean (AbstractAutowireCapableBeanFactory.java:483)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject (AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton (DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean (AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean (AbstractBeanFactory.java:197)
    at org.springframework.context.support.AbstractApplicationContext.getBean (AbstractApplicationContext.java:1081)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization (AbstractApplicationContext.java:856)
    at org.springframework.context.support.AbstractApplicationContext.refresh (AbstractApplicationContext.java:542)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh (EmbeddedWebApplicationContext.java:122)
    at org.springframework.boot.SpringApplication.refresh (SpringApplication.java:737)
    at org.springframework.boot.SpringApplication.refreshContext (SpringApplication.java:370)
    at org.springframework.boot.SpringApplication.run (SpringApplication.java:314)
    at org.springframework.boot.SpringApplication.run (SpringApplication.java:1162)
    at org.springframework.boot.SpringApplication.run (SpringApplication.java:1151)
    at com.example.demo.DemoApplication.main (DemoApplication.java:13)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:566)
    at org.springframework.boot.maven.AbstractRunMojo$LaunchRunner.run (AbstractRunMojo.java:527)
    at java.lang.Thread.run (Thread.java:834)
Caused by: org.hibernate.AnnotationException: mappedBy reference an unknown target entity property: com.example.demo.dao.RedApple.tree in com.example.demo.dao.RedAppleTree.apples
    at org.hibernate.cfg.annotations.CollectionBinder.bindStarToManySecondPass (CollectionBinder.java:769)
    at org.hibernate.cfg.annotations.CollectionBinder$1.secondPass (CollectionBinder.java:719)
    at org.hibernate.cfg.CollectionSecondPass.doSecondPass (CollectionSecondPass.java:54)
    at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processSecondPasses (InFlightMetadataCollectorImpl.java:1655)
    at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processSecondPasses (InFlightMetadataCollectorImpl.java:1623)
    at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete (MetadataBuildingProcess.java:278)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.metadata (EntityManagerFactoryBuilderImpl.java:847)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build (EntityManagerFactoryBuilderImpl.java:874)
    at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory (SpringHibernateJpaPersistenceProvider.java:60)
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory (LocalContainerEntityManagerFactoryBean.java:353)
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory (AbstractEntityManagerFactoryBean.java:370)
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet (AbstractEntityManagerFactoryBean.java:359)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods (AbstractAutowireCapableBeanFactory.java:1687)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean (AbstractAutowireCapableBeanFactory.java:1624)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean (AbstractAutowireCapableBeanFactory.java:555)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean (AbstractAutowireCapableBeanFactory.java:483)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject (AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton (DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean (AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean (AbstractBeanFactory.java:197)
    at org.springframework.context.support.AbstractApplicationContext.getBean (AbstractApplicationContext.java:1081)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization (AbstractApplicationContext.java:856)
    at org.springframework.context.support.AbstractApplicationContext.refresh (AbstractApplicationContext.java:542)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh (EmbeddedWebApplicationContext.java:122)
    at org.springframework.boot.SpringApplication.refresh (SpringApplication.java:737)
    at org.springframework.boot.SpringApplication.refreshContext (SpringApplication.java:370)
    at org.springframework.boot.SpringApplication.run (SpringApplication.java:314)
    at org.springframework.boot.SpringApplication.run (SpringApplication.java:1162)
    at org.springframework.boot.SpringApplication.run (SpringApplication.java:1151)
    at com.example.demo.DemoApplication.main (DemoApplication.java:13)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:566)
    at org.springframework.boot.maven.AbstractRunMojo$LaunchRunner.run (AbstractRunMojo.java:527)
    at java.lang.Thread.run (Thread.java:834)

现在我可以重命名其中一个属性来解决这个问题，但在我正在处理的实际项目中，它会导致更多的更改。

是否可以保持属性名称不变？

java

spring

spring-boot

hibernate

jpa

回答 2

Stack Overflow用户

回答已采纳

发布于 2020-10-23 14:41:36

在你的父类和子类中复制你的"tree“属性是一个问题。我相信这里的例子会做你想要的。

Tree.java

@Entity
@Table(name = "tree")
@DiscriminatorColumn(name = "colour")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public abstract class Tree<APPLE extends Apple> {

    @Id
    @GeneratedValue
    private Long id;

    @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true, mappedBy = "tree", targetEntity = Apple.class)
    private Set<APPLE> apples = Sets.newHashSet();

    //... getters & setters
}

Apple.java

@Table(name = "apple")
@Entity
@DiscriminatorColumn(name = "colour")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public abstract class Apple<TREE extends Tree> {

    @Id
    @GeneratedValue
    private Long id;

    @JoinColumn(name = "tree_id")
    @ManyToOne(targetEntity = Tree.class)
    private TREE tree;

}

RedAppleTree.java

@Entity
@Table(name = "tree")
@DiscriminatorColumn(name = "colour")
@DiscriminatorValue("RED")
public class RedAppleTree extends Tree<RedApple> {
}

RedApple.java

@Entity
@Table(name = "apple")
@DiscriminatorColumn(name = "colour")
@DiscriminatorValue("RED")
public class RedApple extends Apple<RedAppleTree> {
}

这将创建以下DB表

create table tree (
   colour varchar(31) not null,
    id bigint generated by default as identity (start with 1),
    primary key (id)
);
create table apple (
   colour varchar(31) not null,
    id bigint generated by default as identity (start with 1),
    tree_id bigint,
    primary key (id)
)

然后，当我运行以下代码时

@Test
public void test() {

    RedAppleTree tree = new RedAppleTree();
    session.persist(tree);

    GreenAppleTree greenTree = new GreenAppleTree();
    session.persist(greenTree);

    RedApple apple = new RedApple();
    apple.setTree(tree);
    session.persist(apple);

    tree.getApples().add(apple);
    session.flush();
    session.clear();
    
    tree = session.get(RedAppleTree.class, tree.getId());

    System.err.println(session.createCriteria(RedAppleTree.class).list());
}

这将产生以下SQL (在启用hibernate-sql-logging的情况下运行)

Hibernate: 
insert 
into
    tree
    (id, version, colour) 
values
    (default, ?, 'RED')
Hibernate: 
insert 
into
    tree
    (id, version, colour) 
values
    (default, ?, 'GREEN')
Hibernate: 
insert 
into
    apple
    (id, version, tree_id, colour) 
values
    (default, ?, ?, 'RED')
Hibernate: 
select
    redappletr0_.id as id2_409_0_,
    redappletr0_.version as version3_409_0_ 
from
    tree redappletr0_ 
where
    redappletr0_.id=? 
    and redappletr0_.colour='RED'
Hibernate: 
select
    this_.id as id2_409_0_,
    this_.version as version3_409_0_ 
from
    tree this_ 
where
    this_.colour='RED'

我相信这应该可以解决你的基本问题。

票数 1

Stack Overflow用户

发布于 2020-10-14 07:47:36

事实是，我从来没有遇到过类似的问题，合乎逻辑的事情，一个好的做法是更改属性的名称，以区分每个属性引用的实体，编译器会告诉您在哪里更改它。

您可以尝试在关系中指定子类，如下所示：

mappedBy = "tree", targetEntity = RedAppleTree.class

但我重申，最好的选择是更改属性的名称，即使这涉及到更多的工作。

票数 0

页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持

原文链接：

https://stackoverflow.com/questions/64347162

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