通过字段 'employeeDao' 表达的不满足依赖；

Question

I am fresh to spring boot and currently facing this error in STS"Error creating bean with name 'employeeDao': Unsatisfied dependency expressed through field 'sessionfactory'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException"Entity Class@Entity@Table(name = "studenttable")public class Employee {@Id    @GeneratedValue(strategy=GenerationType.AUTO)    private Long id;    @Column(name = "sname")    private String sname;    @Column(name = "scourse")    private String cname;    @Column(name = "sfee")    private Double fee;Hibernate Utils Class    @Configuration    public class HibernateUtilsConfig {        @Autowired        private EntityManagerFactory entityManagerFactory;        @Bean        public SessionFactory getSessionFactoty() {            if(entityManagerFactory.unwrap(SessionFactory.class)== null) {                throw new NullPointerException("Factory Not Found");            }            return entityManagerFactory.unwrap(SessionFactory.class);        }DAO Class@Repositorypublic class EmployeeDao {    @Autowired    private SessionFactory sessionfactory;    public void createEmployee(Employee employee) {        Session session = null;        try {            session = sessionfactory.openSession();            session.beginTransaction();        Integer id=(Integer)    session.save(employee);        System.out.println("The record is add in the system" + id);            session.getTransaction().commit();        }catch (Exception e) {            // TODO: handle exception            e.printStackTrace();        }    }Main Class@SpringBootApplicationpublic class SpringExampleApplication implements CommandLineRunner {    @Autowired    private EmployeeDao employeeDao;    public static void main(String[] args) {        SpringApplication.run(SpringExampleApplication.class, args);    }

Answer 1

您面临的问题是由于HibernateUtilsConfig.java您提供的配置类引起的。在您的 EmployeeDao 类中，您正在自动装配sessionfactorybean。因此，当 springboot 尝试自动装配 bean 时，它会失败并出现以下错误：

Unsatisfied dependency expressed through field 'sessionfactory'; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'hibernateUtilsConfig': Unsatisfied dependency expressed through field 'entityManagerFactory'; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'getSessionFactoty': Requested bean is currently in creation: Is there an unresolvable circular reference?

因为entityManagerFactorybean 不可用。

由于您使用的是 spring-boot ，因此您可能无法手动配置所有内容。您可以通过添加以下依赖项来使用 spring-boot 的默认自动配置：

<dependency>

    <groupId>org.springframework.boot</groupId>

    <artifactId>spring-boot-starter-data-jpa</artifactId>

</dependency>

然后，您可以在 application.properties 或 application.yml 中提供适当的键，spring-boot 将为您配置所有内容。

application.properties

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

spring.datasource.username=mysqluser

spring.datasource.password=mysqlpass

spring.datasource.url=jdbc:mysql://localhost:3306myDb?createDatabaseIfNotExist=true

如果您仍想手动设置所有内容，请尝试创建实体管理器 bean，例如：

   @Bean

   public LocalContainerEntityManagerFactoryBean entityManagerFactory() {

      LocalContainerEntityManagerFactoryBean em 

        = new LocalContainerEntityManagerFactoryBean();

      em.setDataSource(dataSource());

      em.setPackagesToScan(new String[] { "com.example.persistence.model" });

      JpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();

      em.setJpaVendorAdapter(vendorAdapter);

      em.setJpaProperties(additionalProperties());

      return em;

   }