未能延迟初始化角色集合: br.com.coderi.adi.model.Usuario.papeis，无法初始化代理-没有会话

Question

我正在使用Java1.8，在实体、@OneToMany和@ManyToOne之间的关系中使用、Spring和，但是我得到了以下错误：

GRAVE: Servlet.service() for servlet [appServlet] in context with path [/adi] threw exception [Request processing failed; nested exception is org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: br.com.coderi.adi.model.Usuario.papeis, could not initialize proxy - no Session] with root cause
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: br.com.coderi.adi.model.Usuario.papeis, could not initialize proxy - no Session

我可以添加一个用户(Usuario)和他们的角色(Papeis)，但是要执行查询，总是会得到上面的错误。

实体Usuario：

@Entity
public class Usuario {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @NotEmpty
    private String nome;

    @NotEmpty
    private String email;

    @NotEmpty
    @Size(min = 2, max = 25)
    @Column(unique = true)
    private String login;

    @NotEmpty
    @Size(min = 6)
    private String senha;

    @Transient
    private String confirmSenha;

    private Boolean status;

    @OneToMany(mappedBy = "usuario")
    private List<Papel> papeis;

    <!-- Getters/Setters... -->
}

实体Papel：

@Entity
public class Papel {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @NotEmpty
    private String papel;

    @ManyToOne
    private Usuario usuario;

    <!-- Getters/Setters... -->
}

一个用户(Usuario)可以有多个角色(Papel)，各种角色必须属于一个用户。这是正确的方法吗？

服务：

@Service
public class PapelService {

    @Autowired
    private PapelReposiroty papelRepository;

    public Papel getPapel(Integer id) {
        return papelRepository.findOne(id);
    }

    public Papel adicionar(Papel papel) {
        return papelRepository.save(papel);
    }

    public List<Papel> listarPapeisPorUsuario(Usuario usuario) {
        return papelRepository.findPapelByUsuario(usuario);
    }
}

仓库：

@Repository
public interface PapelReposiroty extends CrudRepository<Papel, Integer> {
    public List<Papel> findPapelByUsuario(Usuario usuario);
}

在我的Controller中，在我执行papelService.getPapel(1)时添加了一个用户/角色之后，就会得到这个被引用的错误。谢谢你的帮忙!

Ps:错误只在使用关系方法时发生。

数据库：

​

所有堆栈跟踪：

GRAVE: Servlet.service() for servlet [appServlet] in context with path [/adi] threw exception [Request processing failed; nested exception is org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: br.com.coderi.adi.model.Usuario.papeis, could not initialize proxy - no Session] with root cause
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: br.com.coderi.adi.model.Usuario.papeis, could not initialize proxy - no Session
at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:579)
at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:203)
at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:558)
at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:131)
at org.hibernate.collection.internal.PersistentBag.toString(PersistentBag.java:509)
at java.lang.String.valueOf(String.java:2982)
at java.lang.StringBuilder.append(StringBuilder.java:131)
at br.com.coderi.adi.model.Usuario.toString(Usuario.java:113)
at java.lang.String.valueOf(String.java:2982)
at java.lang.StringBuilder.append(StringBuilder.java:131)
at br.com.coderi.adi.model.Papel.toString(Papel.java:66)
at java.lang.String.valueOf(String.java:2982)
at java.io.PrintStream.println(PrintStream.java:821)
at org.apache.tomcat.util.log.SystemLogHandler.println(SystemLogHandler.java:267)
at br.com.coderi.adi.controller.PapelController.adicionarForm(PapelController.java:39)
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:497)
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:114)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:317)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:127)
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:91)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:115)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:137)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:112)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:169)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:63)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilterInternal(BasicAuthenticationFilter.java:158)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:206)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:121)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.csrf.CsrfFilter.doFilterInternal(CsrfFilter.java:100)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:66)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:56)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:106)
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:214)
at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:177)
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:262)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:673)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1526)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1482)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)

Answer 1

如何在Hibernate中启用延迟加载，在使用hibernate映射和注释的情况下，重述延迟加载的默认行为是非常重要的。 默认行为是急切地加载“属性值”，并延迟加载“集合”。与您可能记得的相反，如果您以前使用过普通的Hibernate 2(映射文件)，默认情况下，所有引用(包括集合)都会被急切地加载。还请注意，@OneToMany和@ManyToMany关联默认为延迟加载；@OneToOne和@ManyToOne默认为热切加载。这一点很重要，请记住，以避免任何陷阱在未来。 要显式启用延迟加载，必须在使用hibernate注释时想要延迟加载的关联上使用"fetch = FetchType.LAZY“。 一个示例用法如下所示： @OneToMany( mappedBy =“类别”，fetch = FetchType.LAZY )私有集产品；与"FetchType.LAZY“平行的另一个属性是"FetchType.EAGER”，它与FetchType.EAGER正好相反，即当首次获取所有者实体时，它也将加载关联实体。 Hibernate中延迟加载的工作方式 Hibernate对实体和关联应用延迟加载行为的最简单方法是提供它们的代理实现。Hibernate通过替换从实体类派生的代理来拦截对实体的调用。在缺少所请求的信息时，将从数据库加载该信息，然后将控制权交给父实体的实现。 请注意，当关联被表示为集合类时，将创建一个包装器(本质上是集合的代理，而不是它包含的实体的代理)，并替换原始集合。当您访问此集合代理时，您在返回的代理集合中得到的不是代理实体，而是实际的实体。您不需要对理解这个概念施加太大的压力，因为在运行时，它并不重要。

您使用@OnetoMany关系。

我知道怎么解决。

使用fetch。

你的实体

@Entity
public class Usuario {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @NotEmpty
    private String nome;

    @NotEmpty
    private String email;

    @NotEmpty
    @Size(min = 2, max = 25)
    @Column(unique = true)
    private String login;

    @NotEmpty
    @Size(min = 6)
    private String senha;

    @Transient
    private String confirmSenha;

    private Boolean status;

    @OneToMany(mappedBy = "usuario")
    private List<Papel> papeis;

    <!-- Getters/Setters... -->
}

你搜索"jpa抓取懒惰“。但。获取，多搜索关系。:)

Answer 2

它不能工作的原因是您的会话即将关闭。这可以在事务结束后自动发生。然后，实体进入“分离”状态。当这种情况发生时，所有对未初始化的惰性代理的访问都将导致这个exception.Of过程，最简单的修复方法就是将IT标记为热切。但是，如果您想保持IT惰性，那么为了修复它，您需要在IT被分离之前在事务中初始化这个集合。如果您不将服务包装在transactin中，则可以使用HQL query子句来确保集合被初始化。如果您遵循以下步骤，则可以保留惰性的FetchType