spring - 为什么我在 Spring-boot 应用程序中通过 SessionFactory 产生循环依赖？

Question

我在启动 Spring-Boot 应用程序时遇到错误。

现在，我想在 DAO 存储库中使用 HibernateDaoSupport，因为 Spring boot 不会自动创建 SessionFactory。因此，我从 EntityManagerFactory 创建了 SessionFactory bean，并尝试在 DAO 类中 Autowiring 它。

但是我得到了以下错误:

Description:

The dependencies of some of the beans in the application context form a cycle:

   fooDao defined in file [/home/user/test/out/production/classes/by/test/testing_the_java_service_layer/repository/FooDao.class]
┌─────┐
|  sessionFactory defined in class path resource [by/test/testing_the_java_service_layer/configuration/Config.class]
└─────┘

我不明白为什么 SessionFactory 是指 FooDao 类。

以下是代码示例:

FooDao.java

@Repository
public class FooDao extends HibernateDaoSupport
{
    @Autowired
    public void setSessionFactories( SessionFactory sessionFactory )
    {
        setSessionFactory( sessionFactory );

    }

    @Transactional
    public int create( Foo entity )
    {
        return (int) this.getHibernateTemplate().save( entity );
    }
}

配置.java

@ComponentScan( basePackages = { "by.test" } )
@Configuration
public class Config
{
    /*
     *     Spring boot doesn't create SessionFactory bean, so we have to create it manually, using EntityManagerFactory
     */
    @Bean
    public SessionFactory sessionFactory( EntityManagerFactory entityManagerFactory )
    {
        return entityManagerFactory.unwrap( SessionFactory.class );
    }
}

Foo.java

@Entity
@Table( name = "bibis" )
public class Foo
{
    @Id
    @Column( name = "foo", nullable = false )
    public int foo;

    @Column( name = "bar" )
    public String bar;
}

TestApplication.java

@SpringBootApplication
public class TestApplication
{

    public static void main( String[] args )
    {
        SpringApplication.run( TestApplication.class, args );
    }
}

application.yaml

spring:
  datasource:
    username: 'bibis'
    password: 'bibis'
    schema: 'bibis'
    host: 'localhost:3306'
    url: 'jdbc:mariadb://localhost:3306/bibis'

和来自 build.gradle 的 gradle 依赖项

implementation('org.mariadb.jdbc:mariadb-java-client')
developmentOnly 'org.springframework.boot:spring-boot-devtools'
compile group: 'org.springframework.boot', name: 'spring-boot-starter-data-jpa', version: '2.1.8.RELEASE'
testImplementation 'org.springframework.boot:spring-boot-starter-test'

我尝试使用@Lazy 注释、构造函数或字段注入(inject)但没有帮助。

Answer 1

我引用了Spring Boot - Handle to Hibernate SessionFactory的答案

从 Config 类返回 HibernateJpaSessionFactoryBean obj 而不是 SessionFactory 对象。

修改后的代码为:

@ComponentScan( basePackages = { "by.test" } )
@Configuration
public class Config
{
    @Bean
    public HibernateJpaSessionFactoryBean sessionFactory(EntityManagerFactory entityManagerFactory)
    {
        HibernateJpaSessionFactoryBean hibernateJpaSessionFactoryBean = new HibernateJpaSessionFactoryBean();
        hibernateJpaSessionFactoryBean.setEntityManagerFactory(entityManagerFactory); 
        return hibernateJpaSessionFactoryBean;
    }
}

---

或者你可以这样做:

@Repository
public class FooDao extends HibernateDaoSupport
{
    @Autowired
    public void setSessionFactories(EntityManagerFactory entityManagerFactory)
    {
        setSessionFactory(entityManagerFactory.unwrap(SessionFactory.class));
    }

    @Transactional
    public int create(Foo entity)
    {
        return (int) this.getHibernateTemplate().save( entity );
    }
}