LazyInitializationException no JPA e no Hibernate
Eu sei que esta pergunta tem sido feita inúmeras vezes aqui e através da internet e eu li muitas dessas respostas, mas ainda não entendi a maneira correta de resolver este problema. Eu estou experimentando com Spring MVC e JPA e cada vez que eu acessar uma propriedade carregada preguiçosamente recebo um LazyInitializationException.
Aqui está um pouco do código que estou experimentando:
@Repository
public class MyDAO {
private static final Logger logger = LoggerFactory.getLogger(MyDAO.class);
@PersistenceContext
private EntityManager em;
@Transactional
public void logDOI() {
DOI myDOI = em.find(DOI.class, Long.valueOf(1));
// This line gives the expected output
logger.info("Fetched DOI: " + myDOI.getDoiKey());
// This line throws the LazyInitalizationException
for(DOIMembership m : myDOI.getDoiMemberships()) {
logger.info("Got DOI Membership id: " + m.getId());
}
}
}
A entidade que estou acessando:
@Entity
@Table(name="DOI")
public class DOI implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@SequenceGenerator(name="DOI_ID_GENERATOR", sequenceName="DOI_SEQ")
@GeneratedValue(strategy=GenerationType.SEQUENCE, generator="DOI_ID_GENERATOR")
private long id;
// Other properties omitted
//bi-directional many-to-one association to DOIMembership
@OneToMany(mappedBy="doi", fetch=FetchType.LAZY)
private Set<DOIMembership> doiMemberships;
public DOI() {
}
public long getId() {
return this.id;
}
public void setId(long id) {
this.id = id;
}
// Other Accessors Omitted
}
A entidade referenciada pelo DOI
@Entity
@Table(name="DOI_MEMBERSHIP")
public class DOIMembership implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@SequenceGenerator(name="DOI_MEMBERSHIP_ID_GENERATOR", sequenceName="DOI_MEMBERSHIP_SEQ")
@GeneratedValue(strategy=GenerationType.SEQUENCE, generator="DOI_MEMBERSHIP_ID_GENERATOR")
private long id;
//bi-directional many-to-one association to DOI
@ManyToOne(fetch=FetchType.LAZY)
@JoinColumn(name="DOI_ID")
private DOI doi;
@Column(name="GROUP_ID")
private BigDecimal groupId;
@Column(name="DATA_SET")
private BigDecimal dataSetId;
public DOIMembership() {
}
public BigDecimal getGroupId() {
return groupId;
}
public BigDecimal getDataSetId() {
return dataSetId;
}
public void setDataSetId(BigDecimal dataSetId) {
this.dataSetId = dataSetId;
}
public void setGroupId(BigDecimal groupId) {
this.groupId = groupId;
}
public long getId() {
return this.id;
}
public void setId(long id) {
this.id = id;
}
public DOI getDoi() {
return this.doi;
}
public void setDoi(DOI doi) {
this.doi = doi;
}
}
O Controlador Spring MVC:
@Controller
@RequestMapping("/summary")
public class DOISummaryController {
@Autowired
MyDAO myDAO;
@RequestMapping()
public String DOISummary() {
myDAO.logDOI();
return "home";
}
}
Minha configuração do Spring:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:task="http://www.springframework.org/schema/task"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-3.1.xsd
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
http://www.springframework.org/schema/task
http://www.springframework.org/schema/task/spring-task-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.1.xsd">
<!-- Root Context: defines shared resources visible to all other web components -->
<context:property-placeholder location="WEB-INF/spring/root-context.properties, WEB-INF/spring/datasource-context.properties" />
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
<property name="driverClassName">
<value>oracle.jdbc.driver.OracleDriver</value>
</property>
<property name="url">
<value>${Url}</value>
</property>
<property name="username">
<value>${Username}</value>
</property>
<property name="password">
<value>${Password}</value>
</property>
</bean>
<bean id="emf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter" />
</property>
<property name="packagesToScan" value="org.myorg.doi.domain" />
<property name="jpaProperties">
<props>
<prop key="hibernate.dialect">
org.hibernate.dialect.Oracle10gDialect
</prop>
<prop key="hibernate.max_fetch_depth">3</prop>
<prop key="hibernate.jdbc.fetch_size">50</prop>
<prop key="hibernate.jdbc.batch_size">10</prop>
<prop key="hibernate.show_sql">true</prop>
</props>
</property>
</bean>
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="emf" />
</bean>
<tx:annotation-driven transaction-manager="transactionManager" />
<context:annotation-config />
<task:annotation-driven />
<context:component-scan base-package="org.myorg.doi" />
</beans>
E um rastreamento de pilha, conforme solicitado:
SEVERE: Servlet.service() for servlet [appServlet] in context with path [/DOI] threw exception [Request processing failed; nested exception is org.hibernate.LazyInitializationException: could not initialize proxy - no Session] with root cause
org.hibernate.LazyInitializationException: could not initialize proxy - no Session
at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:430)
at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:121)
at org.hibernate.collection.internal.PersistentSet.iterator(PersistentSet.java:180)
at org.myorg.doi.dao.MyDAO.logDOI(MyDAO.java:27)
at org.myorg.doi.web.DOISummaryController.DOISummary(DOISummaryController.java:29)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:213)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:126)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at com.springsource.insight.collection.tcserver.request.HttpRequestOperationCollectionValve.traceNextValve(HttpRequestOperationCollectionValve.java:116)
at com.springsource.insight.collection.tcserver.request.HttpRequestOperationCollectionValve.invoke(HttpRequestOperationCollectionValve.java:98)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1001)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:585)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:680)
Eu posso ver, estou tentando usar o JPA puro e apenas usando o Hibernate como um provedor de JPA.
Eu entendo que a exceção é causada pela sessão sendo desanexada da entidade. Mas, pensei que isso não aconteceria se estivéssemos atualmente em uma transação, o que deveria ser o caso, já que o método logDOI é anotado com @Transactional.
Claro, tudo funciona perfeitamente se eu mudar o FetchType para o EAGER, mas parece que eu não deveria ter que fazer isso.
Eu também estou ciente de OpenEntityManagerInViewFilter, mas parece que eu não deveria ter que usar isso se eu mantiver todo o acesso às minhas entidades em um DAO anotado com @Transactional (ou através de outros meios que eu não conheço).
Acho que posso estar abordando esse problema incorretamente, mas não sei qual é a abordagem correta. Como se pode usar efetivamente propriedades carregadas de forma lenta?