懒惰初始化异常：无法初始化代理 - 无会话

java spring-data spring-data-jpa spring-boot

2022-09-03 04:56:10

我使用，我刚刚在MySQL上写了一个CRUD演示，但是在运行时发生了异常，源代码如下：spring-data-jpaspring-boot(v2.0.0.RELEASE)

源码

用户.java

@Entity
public class User implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    private Integer id;
    private String username;
    private String password;

    ...getter&setter
}

用户存储库.java

public interface UserRepository extends JpaRepository<User, Integer> {

}

用户服务测试.java

@RunWith(SpringRunner.class)
@SpringBootTest
public class UserServiceTest {

    @Autowired
    private UserRepository userRepository;

    @Test
    public void getUserById() throws Exception{
        userRepository.getOne(1);
    }

}

应用程序.yml

spring:
  datasource:
    username: ***
    password: ***
    driver-class-name: com.mysql.jdbc.Driver
    url: ********
  thymeleaf:
    cache: false
  jpa:
    show-sql: true
    hibernate:
      ddl-auto: update

异常详细信息

org.hibernate.LazyInitializationException: could not initialize proxy - no Session

at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:155)
at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:268)
at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:73)
at cn.shuaijunlan.sdnsecuritysystem.domain.po.User_$$_jvstc90_0.getUsername(User_$$_jvstc90_0.java)
at cn.shuaijunlan.sdnsecuritysystem.service.UserServiceTest.getUserById(UserServiceTest.java:33)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)

我尝试另一种方法，它可以成功运行。userRepository.findOne(1)

答案 1

可以向测试方法添加注释以避免此异常。@Transactional

方法返回实体的“引用”（代理），可以延迟加载哪些属性。请参阅代码 - 它使用 .从它 javadoc：getOnegetReferenceEntityManager

获取一个实例，其状态可能被懒惰地获取。

在Spring中，实现的是org.hibernate.internal.SessionImpl - 所以没有Session，Spring就无法获得这种方法。EntityManager

要进行会话，您只需创建一个事务...

答案 2

您的测试应如下所示：

@RunWith(SpringRunner.class)    


@SpringBootTest
@Transactional    

public class QuestionTesting {   

    @Test    
    public void test() {    

    }    
}