我一直在尝试从 Spring JPA 中的两个表中查询数据，但没有成功，
当我调用EntityManager.createQuery("").getResultList()时底部提供的调用堆栈触发空指针异常，我有以下类:
Employee.java
@Entity
@Table(name = "employee")
public class Employee implements Serializable{
@Id @GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
@Column(nullable=false, unique=true)
private String name;
@Type(type="org.jadira.usertype.dateandtime.joda.PersistentLocalDateTime")
@Column(name="date_of_birth")
private LocalDateTime dateOfBirth;
private Double salary;
@Column(name="marital_status")
private String maritalStatus;
@DateTimeFormat(pattern="MM/dd/yyyy")
@Column(name="date_of_hire")
@Type(type="org.jadira.usertype.dateandtime.joda.PersistentLocalDateTime")
private LocalDateTime dateOfHire;
private String title;
@ManyToOne()
@JoinColumn(name="dpartment_id")
private Department department;
//security additions
@Column(nullable=false)
private String password;
@OneToMany(fetch=FetchType.EAGER, cascade=CascadeType.ALL)
@JoinColumn(name="employee_id")
private Set<Role> roles = new HashSet<>();
}
部门.java
@Entity
@Table(name = "department")
public class Department implements Serializable{
@Id @GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
@Column(nullable=false, unique=true)
private String name;
@OneToMany(fetch=FetchType.EAGER, cascade=CascadeType.ALL) @JoinColumn(name="department_id")
private Set<Employee> employees = new HashSet<Employee>();
@OneToOne()
@JoinColumn(name="manager_id",nullable=true)
private Employee manager;
}
DepartmentService.java
@Service
@Transactional
public class DepartmentService
{
@PersistenceContext
public EntityManager em;
public List<DepartmentSummary> getDepartmentSummaries( String order ){
Query query= em.createQuery("select new com.me.domain.DepartmentSummary( d, sum(e.salary), count(e.id) ) "
+ " from Department d inner JOIN d.employees e group by d.id ");
List items = query.getResultList();
return items;
}
}
测试用例调用堆栈:
java.lang.NullPointerException
at org.hibernate.engine.internal.StatefulPersistenceContext.getLoadedCollectionOwnerOrNull(StatefulPersistenceContext.java:859)
at org.hibernate.event.spi.AbstractCollectionEvent.getLoadedOwnerOrNull(AbstractCollectionEvent.java:75)
at org.hibernate.event.spi.InitializeCollectionEvent.<init>(InitializeCollectionEvent.java:36)
at org.hibernate.internal.SessionImpl.initializeCollection(SessionImpl.java:1847)
at org.hibernate.collection.internal.AbstractPersistentCollection$4.doWork(AbstractPersistentCollection.java:549)
at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:234)
at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:545)
at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:124)
at org.hibernate.collection.internal.PersistentSet.hashCode(PersistentSet.java:428)
at com.me.entities.Employee.hashCode(Employee.java:27)
at java.util.HashMap.hash(HashMap.java:362)
at java.util.HashMap.put(HashMap.java:492)
at java.util.HashSet.add(HashSet.java:217)
at java.util.AbstractCollection.addAll(AbstractCollection.java:342)
at org.hibernate.collection.internal.PersistentSet.endRead(PersistentSet.java:346)
at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollection(CollectionLoadContext.java:243)
at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:233)
at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:209)
at org.hibernate.loader.Loader.endCollectionLoad(Loader.java:1150)
at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:1119)
at org.hibernate.loader.Loader.processResultSet(Loader.java:964)
at org.hibernate.loader.Loader.doQuery(Loader.java:911)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:342)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:312)
at org.hibernate.loader.Loader.loadEntity(Loader.java:2121)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:82)
at org.hibernate.loader.entity.AbstractEntityLoader.load(AbstractEntityLoader.java:72)
at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:3927)
at org.hibernate.event.internal.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:460)
at org.hibernate.event.internal.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:429)
at org.hibernate.event.internal.DefaultLoadEventListener.load(DefaultLoadEventListener.java:206)
at org.hibernate.event.internal.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:262)
at org.hibernate.event.internal.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:150)
at org.hibernate.internal.SessionImpl.fireLoad(SessionImpl.java:1092)
at org.hibernate.internal.SessionImpl.internalLoad(SessionImpl.java:1019)
at org.hibernate.type.EntityType.resolveIdentifier(EntityType.java:672)
at org.hibernate.type.EntityType.resolve(EntityType.java:490)
at org.hibernate.type.EntityType.nullSafeGet(EntityType.java:290)
at org.hibernate.loader.hql.QueryLoader.getResultRow(QueryLoader.java:446)
at org.hibernate.loader.hql.QueryLoader.getResultColumnOrRow(QueryLoader.java:429)
at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:741)
at org.hibernate.loader.Loader.processResultSet(Loader.java:943)
at org.hibernate.loader.Loader.doQuery(Loader.java:911)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:342)
at org.hibernate.loader.Loader.doList(Loader.java:2526)
at org.hibernate.loader.Loader.doList(Loader.java:2512)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2342)
at org.hibernate.loader.Loader.list(Loader.java:2337)
at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:495)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:357)
at org.hibernate.engine.query.spi.HQLQueryPlan.performList(HQLQueryPlan.java:195)
at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1269)
at org.hibernate.internal.QueryImpl.list(QueryImpl.java:101)
at org.hibernate.ejb.QueryImpl.getResultList(QueryImpl.java:268)
at com.me.services.DepartmentService.getDepartmentSummaries(DepartmentService.java:72)
at com.me.services.DepartmentService$$FastClassByCGLIB$$fbe553f5.invoke(<generated>)
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:713)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:98)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:262)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:95)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:646)
at com.me.services.DepartmentService$$EnhancerByCGLIB$$a1dbb849.getDepartmentSummaries(<generated>)
at com.me.DepartmentServiceTest.getDepartmentSummaries(DepartmentServiceTest.java:72)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:74)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:83)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:232)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:89)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:175)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
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:675)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
最佳答案
实际上，问题是 hibernate jars 版本和 spring JPA jars 版本之间不兼容。使用最新的 spring 和 hibernate 版本更新我的 Maven 后，一切运行良好。我希望这对将来的任何人都有帮助。
关于java - Spring JPA从多个表中获取数据，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/26316238/