java - 无法运行 Springboot JPA
问题描述
我正在尝试一个简单的 Spring Data JPA 应用程序来连接数据库并从表中获取数据。我正在使用使用 JpaRepository 的存储库接口。在运行应用程序时,它不允许我们启动服务器并显示以下错误。
下面是我的界面
package com.thiluxan.springjpa;
import org.springframework.data.jpa.repository.JpaRepository;
import com.thiluxan.springjpa.model.Student;
public interface StudentRepo extends JpaRepository<Student, Integer> {
}
下面是我的控制器类
@Controller
public class HomeController {
@Autowired
StudentRepo repo;
@RequestMapping("/view")
public String viewStudents(Model m) {
m.addAttribute("students", repo.findAll());
return "display";
}
}
下面是我的实体类
@Entity
public class Student {
@Id
private int id;
private String name;
public Student() {}
public Student(int id, String name) {
super();
this.id = id;
this.name = name;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "Student [id=" + id + ", name=" + name + "]\n";
}
}
编译器显示以下错误:
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'studentRepo' defined in com.thiluxan.springjpa.StudentRepo defined in @EnableJpaRepositories declared on JpaRepositoriesRegistrar.EnableJpaRepositoriesConfiguration: Cannot resolve reference to bean 'jpaMappingContext' while setting bean property 'mappingContext'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jpaMappingContext': Invocation of init method failed; nested exception is org.hibernate.AnnotationException: No identifier specified for entity: com.thiluxan.springjpa.model.Student
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:342) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:113) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1697) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1442) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:226) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeansOfType(DefaultListableBeanFactory.java:624) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeansOfType(DefaultListableBeanFactory.java:612) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.data.repository.config.DeferredRepositoryInitializationListener.onApplicationEvent(DeferredRepositoryInitializationListener.java:51) ~[spring-data-commons-2.3.2.RELEASE.jar:2.3.2.RELEASE]
at org.springframework.data.repository.config.DeferredRepositoryInitializationListener.onApplicationEvent(DeferredRepositoryInitializationListener.java:36) ~[spring-data-commons-2.3.2.RELEASE.jar:2.3.2.RELEASE]
at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172) ~[spring-context-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165) ~[spring-context-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139) ~[spring-context-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:404) ~[spring-context-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:361) ~[spring-context-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:898) ~[spring-context-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:554) ~[spring-context-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:143) ~[spring-boot-2.3.2.RELEASE.jar:2.3.2.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:758) [spring-boot-2.3.2.RELEASE.jar:2.3.2.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:750) [spring-boot-2.3.2.RELEASE.jar:2.3.2.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) [spring-boot-2.3.2.RELEASE.jar:2.3.2.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) [spring-boot-2.3.2.RELEASE.jar:2.3.2.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1237) [spring-boot-2.3.2.RELEASE.jar:2.3.2.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) [spring-boot-2.3.2.RELEASE.jar:2.3.2.RELEASE]
at com.thiluxan.springjpa.SpringJPAApplication.main(SpringJPAApplication.java:12) [classes/:na]
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jpaMappingContext': Invocation of init method failed; nested exception is org.hibernate.AnnotationException: No identifier specified for entity: com.thiluxan.springjpa.model.Student
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1794) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:594) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:226) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:330) ~[spring-beans-5.2.8.RELEASE.jar:5.2.8.RELEASE]
... 28 common frames omitted
Caused by: org.hibernate.AnnotationException: No identifier specified for entity: com.thiluxan.springjpa.model.Student
at org.hibernate.cfg.InheritanceState.determineDefaultAccessType(InheritanceState.java:266) ~[hibernate-core-5.4.18.Final.jar:5.4.18.Final]
at org.hibernate.cfg.InheritanceState.getElementsToProcess(InheritanceState.java:211) ~[hibernate-core-5.4.18.Final.jar:5.4.18.Final]
at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:781) ~[hibernate-core-5.4.18.Final.jar:5.4.18.Final]
at org.hibernate.boot.model.source.internal.annotations.AnnotationMetadataSourceProcessorImpl.processEntityHierarchies(AnnotationMetadataSourceProcessorImpl.java:254) ~[hibernate-core-5.4.18.Final.jar:5.4.18.Final]
at org.hibernate.boot.model.process.spi.MetadataBuildingProcess$1.processEntityHierarchies(MetadataBuildingProcess.java:230) ~[hibernate-core-5.4.18.Final.jar:5.4.18.Final]
at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:273) ~[hibernate-core-5.4.18.Final.jar:5.4.18.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.metadata(EntityManagerFactoryBuilderImpl.java:1224) ~[hibernate-core-5.4.18.Final.jar:5.4.18.Final]
at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:1255) ~[hibernate-core-5.4.18.Final.jar:5.4.18.Final]
at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:58) ~[spring-orm-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) ~[spring-orm-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:391) ~[spring-orm-5.2.8.RELEASE.jar:5.2.8.RELEASE]
at java.util.concurrent.FutureTask.run(Unknown Source) ~[na:1.8.0_241]
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) ~[na:1.8.0_241]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) ~[na:1.8.0_241]
at java.lang.Thread.run(Unknown Source) ~[na:1.8.0_241]
解决方案
JPA 规范支持四种不同的生成主键的主键生成策略。
@GeneratedValue(strategy = GenerationType.AUTO)
@GeneratedValue(strategy = GenerationType.IDENTITY)
@GeneratedValue(strategy = GenerationType.SEQUENCE)
@GeneratedValue(strategy = GenerationType.TABLE)
@Entity
public class Student {
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "student_generator")
@SequenceGenerator(name = "student_generator", sequenceName = "stu_seq",allocationSize = 1)
private int id;
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