我用 spring-data-jpa
与 spring-boot(v2.0.0.RELEASE)
,我刚刚在MySQL上写了一个CRUD的demo,但是运行时出现异常,源码如下:
源代码
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);
}
}
application.yml
spring:
datasource:
username: ***
password: ***
driver-class-name: com.mysql.jdbc.Driver
url: ********
thymeleaf:
cache: false
jpa:
show-sql: true
hibernate:
ddl-auto: update
异常详情
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)
I try to another method
userRepository.findOne(1)
, it can run successfully.
最佳答案
您可以添加 @Transactional
注释到您的测试方法以避免此异常。
方法getOne
返回可以延迟加载属性的实体的“引用”(代理)。看到它code - 它使用 getReference
EntityManager
的方法.从它javadoc:
Get an instance, whose state may be lazily fetched.
在 Spring 中实现
EntityManager
是 org.hibernate.internal.SessionImpl - 所以如果没有 Session Spring 就无法获得这个方法。要进行 session ,您只需创建一个事务...
关于java - 延迟初始化异常 : could not initialize proxy - no Session,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/49894587/