解決Spring Data JPA延遲加載could not initialize proxy - no Session 錯誤

項目采用spring boot構建，提供restful接口給PHP調用，接口類統一使用@RestController注解

 

實體關系

 

@ManyToOne(fetch = FetchType.LAZY)

@JoinColumn(name = "department_id")
private Department department;

 

 

 

@OneToMany(mappedBy = "department", fetch = FetchType.LAZY)
private Set<Employee> employees;

 

單元測試

@Test
public void testGet() {
    Department dept = deptService.get(1L);
    Assert.assertEquals("IT", dept.getName());
    Set<Employee> employees = dept.getEmployees();
    Assert.assertEquals(2, employees.size());
}

 

 

異常信息

 

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.ai.demo.entity.Department.employees, could not initialize proxy - no Session
    at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:587)
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:204)
    at org.hibernate.collection.internal.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:148)
    at org.hibernate.collection.internal.PersistentSet.size(PersistentSet.java:143)
    at com.ai.demo.service.DepartmentServiceTests.testGet(DepartmentServiceTests.java:37)
    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)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:252)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:678)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)

 

解決LazyInitializationException異常大概有這么幾種方式
1.關閉LazyInitialization, 將fetch設成eager

2.在spring boot的配置文件application.properties添加spring.jpa.open-in-view=true

3.用spring 的OpenSessionInViewFilter

第一種方式顯然不好，無法使用到延遲加載的特性，會帶來性能問題

后面兩種方式只能用在Servlet容器下,而當我們在spring boot環境下運行單元測試的時候是無法啟用OpenSessionInViewFilter的

 

其實要解決這種情況下的問題也很簡單，只需要在單元測試方法@Transactional注解即可解決

 

@Test
@Transactional
public void testGet() {
    Department dept = deptService.get(1L);
    Assert.assertEquals("IT", dept.getName());
    Set<Employee> employees = dept.getEmployees();
    Assert.assertEquals(2, employees.size());
}