Unable to run the Springboot JPA

Question

I'm trying a simple Spring Data JPA application to connect with a database and fetch data from the table. I'm using the repository interface which is using JpaRepository. while running the application, it doesn't allow us to start the server and shows the below error.

Below is my interface

package com.thiluxan.springjpa;

import org.springframework.data.jpa.repository.JpaRepository;

import com.thiluxan.springjpa.model.Student;

public interface StudentRepo extends JpaRepository<Student, Integer> {

}

Below is my controller class

@Controller
public class HomeController {
    
    @Autowired
    StudentRepo repo;
    
    @RequestMapping("/view")
    public String viewStudents(Model m) {
        
        m.addAttribute("students", repo.findAll());
        return "display";
    }
}

Below is my Entity Class

@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";
    }
    
    
}

And the compiler shows the below error:

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]

Answer 1

The JPA specification supports four different primary key generation strategies that generate the primary key.

@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;

Answer 2

Try after adding @Repository annotation to your interface StudentRepo