创建名为"entityManagerFactory "的 bean 时出错 - 嵌套异常是 java.lang.NullPointerException

Question

我只学习Java和Spring，在几个项目/教程进行得很顺利之后，我在一个新项目中遇到了这个错误:

org.springframework.beans.factory。BeanCreationException:错误创建在类路径中定义名为"entityManagerFactory"的bean资源[org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]:init方法调用失败;嵌套异常是java.lang.NullPointerException

我搜索并检查了stackoverflow问题，但在任何情况下都没有看到嵌套异常是java.lang. nullpointerexception。对我来说，这是一个相当模糊的错误信息，所以我不明白是什么导致错误。

这是我的pom.xml文件

<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.6.7</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>shoptest</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>shoptest</name>
<description>Shop Test for my project</description>
<properties>
<java.version>11</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-hateoas</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.22</version>
<scope>provided</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

编辑:堆栈跟踪:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Invocation of init method failed; nested exception is java.lang.NullPointerException
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1804) ~[spring-beans-5.3.19.jar:5.3.19]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:620) ~[spring-beans-5.3.19.jar:5.3.19]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:542) ~[spring-beans-5.3.19.jar:5.3.19]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.19.jar:5.3.19]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.19.jar:5.3.19]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.19.jar:5.3.19]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.19.jar:5.3.19]
at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1154) ~[spring-context-5.3.19.jar:5.3.19]
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:908) ~[spring-context-5.3.19.jar:5.3.19]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:583) ~[spring-context-5.3.19.jar:5.3.19]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:145) ~[spring-boot-2.6.7.jar:2.6.7]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:740) ~[spring-boot-2.6.7.jar:2.6.7]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:415) ~[spring-boot-2.6.7.jar:2.6.7]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) ~[spring-boot-2.6.7.jar:2.6.7]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1312) ~[spring-boot-2.6.7.jar:2.6.7]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1301) ~[spring-boot-2.6.7.jar:2.6.7]
at com.example.shoptest.ShoptestApplication.main(ShoptestApplication.java:10) ~[classes/:na]
Caused by: java.lang.NullPointerException: null
at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processFkSecondPassesInOrder(InFlightMetadataCollectorImpl.java:1672) ~[hibernate-core-5.6.8.Final.jar:5.6.8.Final]
at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processSecondPasses(InFlightMetadataCollectorImpl.java:1623) ~[hibernate-core-5.6.8.Final.jar:5.6.8.Final]
at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:295) ~[hibernate-core-5.6.8.Final.jar:5.6.8.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.metadata(EntityManagerFactoryBuilderImpl.java:1460) ~[hibernate-core-5.6.8.Final.jar:5.6.8.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:1494) ~[hibernate-core-5.6.8.Final.jar:5.6.8.Final]
at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:58) ~[spring-orm-5.3.19.jar:5.3.19]
at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) ~[spring-orm-5.3.19.jar:5.3.19]
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:409) ~[spring-orm-5.3.19.jar:5.3.19]
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:396) ~[spring-orm-5.3.19.jar:5.3.19]
at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.afterPropertiesSet(LocalContainerEntityManagerFactoryBean.java:341) ~[spring-orm-5.3.19.jar:5.3.19]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1863) ~[spring-beans-5.3.19.jar:5.3.19]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1800) ~[spring-beans-5.3.19.jar:5.3.19]
... 16 common frames omitted

Answer 1

原因是组合键的嵌入式类中的字段类型错误。我原以为我必须引用另一个实体的Id列及其类型，但我必须引用整个对象。

所以这个实现

public class OrderItemPK implements Serializable {
@ManyToOne
@JoinColumn(name="ORDER_ID")
private **Long** orderId;
@ManyToOne
@JoinColumn(name="PRODUCT_ID")
private **Long** productId;

应该是这样的:

public class OrderItemPK implements Serializable {
@ManyToOne
@JoinColumn(name="ORDER_ID")
private **Order** order;
@ManyToOne
@JoinColumn(name="PRODUCT_ID")
private **Product** product;

Answer 2

此NPE可能是由JPA实体模型定义中的Hibernate无法处理的某些内容引起的。这可能是JPA实体定义中的错误配置(当然也可能是其他东西)。

为了进行更深入的研究，您可以做的一个修改是为hibernate类启用调试甚至跟踪日志记录。这可能会给你一些很好的提示，告诉你去哪里看。

另外，您的JPA实体模型非常复杂吗?你能把它贴在这里吗?