java - 添加实体列表时的Spring Data jpa( hibernate )空指针异常

Question

首先是我的代码。

特化

@Entity
public class Specialization {

    @Id
    private String name;

    @OneToMany(cascade = CascadeType.ALL)
    @JoinColumn(name="att_id", referencedColumnName="ID")
    private List<Attribute> attributes;

    //Getters and Setters
}

属性

@Entity
public class Attribute {

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

    private String name;
    private double scaling;

    //Getters and Setters
}

我的问题是出现以下异常:

Caused by: java.lang.NullPointerException
    at org.hibernate.cfg.annotations.CollectionBinder.bindCollectionSecondPass(CollectionBinder.java:1460)
    at org.hibernate.cfg.annotations.CollectionBinder.bindOneToManySecondPass(CollectionBinder.java:864)
    at org.hibernate.cfg.annotations.CollectionBinder.bindStarToManySecondPass(CollectionBinder.java:779)
    at org.hibernate.cfg.annotations.CollectionBinder$1.secondPass(CollectionBinder.java:728)
    at org.hibernate.cfg.CollectionSecondPass.doSecondPass(CollectionSecondPass.java:70)
    at org.hibernate.cfg.Configuration.originalSecondPassCompile(Configuration.java:1697)
    at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1426)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1846)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:852)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:845)
    at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.withTccl(ClassLoaderServiceImpl.java:398)
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:844)
    at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:60)
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:343)
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:318)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1625)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1562)
    ... 98 more

此异常仅在将属性 attributes 添加到类 Specialization 后发生。所以没有这个属性一切正常，但是如果我添加这个属性，就会出现异常。我不明白我做错了什么。也许有人能发现我的错误？

附加信息:

Hibernate 核心版本:4.3.7。最终。

还有另一个实体 GameClass 与 Specialization 具有一对多关系 => 每个 GameClass 都有多个 Specialization 并且每个 Specialization 有多个 Attribute。

不知道这是否重要，但这是一个 Spring-Boot 应用程序

Answer 1

我错了。睡一点有帮助。我混淆了这些关系。

如果一个Specialization有很多Attribute，注解应该是这样的:

@OneToMany(cascade = CascadeType.ALL)
@JoinColumn(name="specc_id", referencedColumnName = "name")
private List<Attribute> attributes;

并且不这样:

@OneToMany(cascade = CascadeType.ALL)
@JoinColumn(name="att_id", referencedColumnName="ID")
private List<Attribute> attributes;