java - Hibernate ElementCollection(fetch=FetchType.EAGER) 导致 PropertyAccessException

Question

我使用 spring-boot-1.5.3 和 spring-data-jpa，有两个实体，它们在 cloumn tags 和 nicknames 上都有 JPA Annoatation ElementCollection，Hibernate 会根据实体自动生成表。参见Job.java表的默认CollectionTable是主键job_id，但我更改为job_name，集合tags可以为空。那就是异常发生的时候。

名为 Job2 的作业没有任何标签，这意味着 Settags 为空。当我使用 jobDao.findOne(3); 获取 Job2 时，Hibernate 抛出异常org.hibernate.property.access.spi.PropertyAccessException引起:java.lang.IllegalArgumentException:无法将 java.lang.String 字段 hello.entity.Job.name 设置为 java.lang.Integer

当我将 @ElementCollection(fetch=FetchType.EAGER) 更改为 @ElementCollection(fetch = FetchType.LAZY) 时，一切顺利。但我不知道为什么当一个实体的 Collection 列中没有元素时 FetchType.EAGER 会导致异常。并且，即使 hibernate 应该知道使用 name 而不是 id，它仍然尝试将 job.name 转换为 job.id完整的堆栈跟踪是

org.springframework.orm.jpa.JpaSystemException: Error accessing field [private java.lang.String hello.entity.Job.name] by reflection for persistent property [hello.entity.Job#name] : 3; nested exception is org.hibernate.property.access.spi.PropertyAccessException: Error accessing field [private java.lang.String hello.entity.Job.name] by reflection for persistent property [hello.entity.Job#name] : 3
    at org.springframework.orm.jpa.vendor.HibernateJpaDialect.convertHibernateAccessException(HibernateJpaDialect.java:333)
    at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:244)
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:488)
    at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:59)
    at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:213)
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:147)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:133)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.data.repository.core.support.SurroundingTransactionDetectorMethodInterceptor.invoke(SurroundingTransactionDetectorMethodInterceptor.java:57)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213)
    at com.sun.proxy.$Proxy115.findOne(Unknown Source)
    at hello.ApplicationTests.testJob2(ApplicationTests.java:67)
    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)
Caused by: org.hibernate.property.access.spi.PropertyAccessException: Error accessing field [private java.lang.String hello.entity.Job.name] by reflection for persistent property [hello.entity.Job#name] : 3
    at org.hibernate.property.access.spi.GetterFieldImpl.get(GetterFieldImpl.java:43)
    at org.hibernate.tuple.component.AbstractComponentTuplizer.getPropertyValue(AbstractComponentTuplizer.java:58)
    at org.hibernate.type.ComponentType.getPropertyValue(ComponentType.java:419)
    at org.hibernate.type.ComponentType.getHashCode(ComponentType.java:242)
    at org.hibernate.engine.spi.CollectionKey.generateHashCode(CollectionKey.java:64)
    at org.hibernate.engine.spi.CollectionKey.<init>(CollectionKey.java:58)
    at org.hibernate.engine.spi.CollectionKey.<init>(CollectionKey.java:43)
    at org.hibernate.engine.loading.internal.CollectionLoadContext.getLoadingCollection(CollectionLoadContext.java:95)
    at org.hibernate.loader.plan.exec.process.internal.CollectionReferenceInitializerImpl.finishUpRow(CollectionReferenceInitializerImpl.java:105)
    at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.readRow(AbstractRowReader.java:121)
    at org.hibernate.loader.plan.exec.internal.EntityLoadQueryDetails$EntityLoaderRowReader.readRow(EntityLoadQueryDetails.java:239)
    at org.hibernate.loader.plan.exec.process.internal.ResultSetProcessorImpl.extractResults(ResultSetProcessorImpl.java:122)
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:122)
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:86)
    at org.hibernate.loader.entity.plan.AbstractLoadPlanBasedEntityLoader.load(AbstractLoadPlanBasedEntityLoader.java:167)
    at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:4019)
    at org.hibernate.event.internal.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:508)
    at org.hibernate.event.internal.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:478)
    at org.hibernate.event.internal.DefaultLoadEventListener.load(DefaultLoadEventListener.java:219)
    at org.hibernate.event.internal.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:278)
    at org.hibernate.event.internal.DefaultLoadEventListener.doOnLoad(DefaultLoadEventListener.java:121)
    at org.hibernate.event.internal.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:89)
    at org.hibernate.internal.SessionImpl.fireLoad(SessionImpl.java:1129)
    at org.hibernate.internal.SessionImpl.access$2600(SessionImpl.java:164)
    at org.hibernate.internal.SessionImpl$IdentifierLoadAccessImpl.load(SessionImpl.java:2696)
    at org.hibernate.internal.SessionImpl.get(SessionImpl.java:975)
    at org.hibernate.jpa.spi.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:1075)
    at org.hibernate.jpa.spi.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:1039)
    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.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:298)
    at com.sun.proxy.$Proxy101.find(Unknown Source)
    at org.springframework.data.jpa.repository.support.SimpleJpaRepository.findOne(SimpleJpaRepository.java:241)
    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.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.executeMethodOn(RepositoryFactorySupport.java:504)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:489)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:461)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:61)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:282)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:136)
    ... 39 more
Caused by: java.lang.IllegalArgumentException: Can not set java.lang.String field hello.entity.Job.name to java.lang.Integer
    at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167)
    at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171)
    at sun.reflect.UnsafeFieldAccessorImpl.ensureObj(UnsafeFieldAccessorImpl.java:58)
    at sun.reflect.UnsafeObjectFieldAccessorImpl.get(UnsafeObjectFieldAccessorImpl.java:36)
    at java.lang.reflect.Field.get(Field.java:393)
    at org.hibernate.property.access.spi.GetterFieldImpl.get(GetterFieldImpl.java:39)
    ... 88 more



mysql> select * from employee;
+----+------+
| id | name |
+----+------+
|  2 | E1   |
|  3 | E2   |
+----+------+
2 rows in set

mysql> select * from employee_nick_names;
+-------------+------------+
| employee_id | nick_names |
+-------------+------------+
|           2 | E1A        |
|           2 | E1B        |
+-------------+------------+
2 rows in set

mysql> select * from job;
+----+------+
| id | name |
+----+------+
|  2 | Job1 |
|  3 | Job2 |
+----+------+
2 rows in set

mysql> select * from job_tags;
+----------+---------+
| job_name | job_tag |
+----------+---------+
| Job1     | Tag1    |
| Job1     | Tag2    |
+----------+---------+
2 rows in set

作业.java

@Entity
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Job implements Serializable {
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue
    private Integer id;
    private String name;

    @ElementCollection(fetch=FetchType.EAGER)
//  @ElementCollection(fetch = FetchType.LAZY)
    @CollectionTable(name = "job_tags", joinColumns = @JoinColumn(name = "job_name", referencedColumnName = "name"))
    @Column(name = "job_tag")
    private Set<String> tags = new HashSet<String>();
}

员工.java

@Entity
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Employee implements Serializable {
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue
    private Integer id;
    private String name;

    @ElementCollection(fetch=FetchType.EAGER)
//  @ElementCollection(fetch = FetchType.LAZY)
    private Set<String> nickNames = new HashSet<String>();
}

JobDao.java

public interface JobDao extends JpaRepository<Job, Integer> {}

EmployeeDao.java

public interface EmployeeDao extends JpaRepository<Employee, Integer> {}

ApplocationTest.java

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

    @Autowired
    JobDao jobDao;
    @Autowired
    EmployeeDao employeeDao;

    @Test
    public void testEmployee() {
        employeeDao.findAll().forEach(e -> employeeDao.delete(e));

        Employee e1 = new Employee();
        e1.setName("E1");
        e1.setNickNames(Sets.newSet("E1A", "E1B"));
        employeeDao.save(e1);

        Employee e2 = new Employee();
        e2.setName("E2");
        employeeDao.save(e2);
    }

    @Test
    @Transactional
    public void testEmployee2() {
        Employee employee1 = employeeDao.findOne(2);
        System.out.println(employee2);
        Employee employee2 = employeeDao.findOne(3);
        System.out.println(employee3);
    }

    @Test
    public void testJob() {
        jobDao.findAll().forEach(e -> jobDao.delete(e));

        Job job1 = new Job();
        job1.setName("Job1");
        job1.setTags(Sets.newSet("Tag1", "Tag2"));
        jobDao.save(job1);

        Job job2 = new Job();
        job2.setName("Job2");
        jobDao.save(job2);
    }

    @Test
    @Transactional
    public void testJob2() {
        Job job1 = jobDao.findOne(2);
        System.out.println(job2);
        Job job2 = jobDao.findOne(3);
        System.out.println(job3);
    }
}

Answer 1

当您查询职位时

渴望

hibernate将立即获取“job_tags”

并获取名称字段的值，

但是name字段是私有(private)的==>访问被拒绝，您可以尝试将name字段更改为公开

使用 LAZY

hibernate获取作业表单数据库(并且不获取“job_tags”)

当你隐式调用 getter getJobTags 时，job_tags 将被加载