java.lang.IllegalArgumentException: Not a managed type: class models.User

Question

I am doing Spring + mysql application. When I run the application I am getting some exceptions.

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2020-11-26 17:06:37.279 ERROR 3192 --- [           main] o.s.boot.SpringApplication               : Application run failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userRepository': FactoryBean threw exception on object creation; nested exception is java.lang.IllegalArgumentException: Not a managed type: class models.User
    at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:176) ~[spring-beans-5.3.1.jar:5.3.1]
    at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:101) ~[spring-beans-5.3.1.jar:5.3.1]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getObjectForBeanInstance(AbstractBeanFactory.java:1879) ~[spring-beans-5.3.1.jar:5.3.1]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getObjectForBeanInstance(AbstractAutowireCapableBeanFactory.java:1268) ~[spring-beans-5.3.1.jar:5.3.1]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:345) ~[spring-beans-5.3.1.jar:5.3.1]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.1.jar:5.3.1]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeansOfType(DefaultListableBeanFactory.java:671) ~[spring-beans-5.3.1.jar:5.3.1]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeansOfType(DefaultListableBeanFactory.java:659) ~[spring-beans-5.3.1.jar:5.3.1]
    at org.springframework.data.repository.config.DeferredRepositoryInitializationListener.onApplicationEvent(DeferredRepositoryInitializationListener.java:53) ~[spring-data-commons-2.4.1.jar:2.4.1]
    at org.springframework.data.repository.config.DeferredRepositoryInitializationListener.onApplicationEvent(DeferredRepositoryInitializationListener.java:35) ~[spring-data-commons-2.4.1.jar:2.4.1]
    at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:203) ~[spring-context-5.3.1.jar:5.3.1]
    at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:196) ~[spring-context-5.3.1.jar:5.3.1]
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:161) ~[spring-context-5.3.1.jar:5.3.1]
    at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:426) ~[spring-context-5.3.1.jar:5.3.1]
    at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:383) ~[spring-context-5.3.1.jar:5.3.1]
    at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:945) ~[spring-context-5.3.1.jar:5.3.1]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:591) ~[spring-context-5.3.1.jar:5.3.1]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:144) ~[spring-boot-2.4.0.jar:2.4.0]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:767) ~[spring-boot-2.4.0.jar:2.4.0]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:759) ~[spring-boot-2.4.0.jar:2.4.0]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:426) ~[spring-boot-2.4.0.jar:2.4.0]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:326) ~[spring-boot-2.4.0.jar:2.4.0]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1309) ~[spring-boot-2.4.0.jar:2.4.0]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1298) ~[spring-boot-2.4.0.jar:2.4.0]
    at com.example.demo.MotasemDiab1162106exp10Application.main(MotasemDiab1162106exp10Application.java:10) ~[classes/:na]
Caused by: java.lang.IllegalArgumentException: Not a managed type: class models.User
    at org.hibernate.metamodel.internal.MetamodelImpl.managedType(MetamodelImpl.java:582) ~[hibernate-core-5.4.23.Final.jar:5.4.23.Final]
    at org.hibernate.metamodel.internal.MetamodelImpl.managedType(MetamodelImpl.java:85) ~[hibernate-core-5.4.23.Final.jar:5.4.23.Final]
    at org.springframework.data.jpa.repository.support.JpaMetamodelEntityInformation.<init>(JpaMetamodelEntityInformation.java:75) ~[spring-data-jpa-2.4.1.jar:2.4.1]
    at org.springframework.data.jpa.repository.support.JpaEntityInformationSupport.getEntityInformation(JpaEntityInformationSupport.java:66) ~[spring-data-jpa-2.4.1.jar:2.4.1]
    at org.springframework.data.jpa.repository.support.JpaRepositoryFactory.getEntityInformation(JpaRepositoryFactory.java:229) ~[spring-data-jpa-2.4.1.jar:2.4.1]
    at org.springframework.data.jpa.repository.support.JpaRepositoryFactory.getTargetRepository(JpaRepositoryFactory.java:179) ~[spring-data-jpa-2.4.1.jar:2.4.1]
    at org.springframework.data.jpa.repository.support.JpaRepositoryFactory.getTargetRepository(JpaRepositoryFactory.java:162) ~[spring-data-jpa-2.4.1.jar:2.4.1]
    at org.springframework.data.jpa.repository.support.JpaRepositoryFactory.getTargetRepository(JpaRepositoryFactory.java:72) ~[spring-data-jpa-2.4.1.jar:2.4.1]
    at org.springframework.data.repository.core.support.RepositoryFactorySupport.getRepository(RepositoryFactorySupport.java:281) ~[spring-data-commons-2.4.1.jar:2.4.1]
    at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.lambda$afterPropertiesSet$6(RepositoryFactoryBeanSupport.java:326) ~[spring-data-commons-2.4.1.jar:2.4.1]
    at org.springframework.data.util.Lazy.getNullable(Lazy.java:230) ~[spring-data-commons-2.4.1.jar:2.4.1]
    at org.springframework.data.util.Lazy.get(Lazy.java:114) ~[spring-data-commons-2.4.1.jar:2.4.1]
    at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.getObject(RepositoryFactoryBeanSupport.java:271) ~[spring-data-commons-2.4.1.jar:2.4.1]
    at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.getObject(RepositoryFactoryBeanSupport.java:58) ~[spring-data-commons-2.4.1.jar:2.4.1]

The following is my User class:

@Entity
@Table(name = "users")
public class User {
    
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO) 
    @Column (name="user_id")
    private Integer id;
    
    @Column(nullable = false, unique = true) 
    private String userName;
    
    public User(Integer id, String userName) {
        this.id = id;
        this.userName = userName;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    
}

Answer 1

Your User class should be in the models package according to the error message. Make sure it is.

eg

package models

@Entity
@Table(name = "users")
public class User {
    
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO) 
    @Column (name="user_id")
    private Integer id;
    
    @Column(nullable = false, unique = true) 
    private String userName;
    
    public User(Integer id, String userName) {
        this.id = id;
        this.userName = userName;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }    
}

Answer 2

You should declare on your configuration class path to your models(entities)

@EntityScan(basePackages = {
        "com.path.to.your.model",
        "com.path.to.your.another.model"})

from package

org.springframework.boot.autoconfigure.domain.EntityScan;