org.hibernate.LazyInitializationException关联集合

Question

我有两个与多对多关系相关的模型类：

@Entity
@XmlRootElement
@DynamicInsert (value = true)
@DynamicUpdate (value = true)
public class Matchs {

    @Id @GeneratedValue
    private Long matchId;
    private int size;
    private Date begins;
    private Date cutOff;
    private BigDecimal buyIn;

    @ManyToMany
    private List<Users> users;
}

@Entity
@XmlRootElement
@DynamicInsert (value = true)
@DynamicUpdate (value = true)
public class Users {

    @Id
    private String username;
    private String lastName,firstName,password,email;

    private Date dateOfBirth;

    @ManyToMany
    private List<Matchs> matchs;
}

我正在使用DAO与所有相关用户进行匹配：

public Matchs findMatchWithUsers(long matchId) 
{
    if (matchId <= 0)
        throw new IllegalArgumentException("Match Id cannot be less than or equal to zero");

    try {
        begin();
        Matchs match = (Matchs) getSession().get(Matchs.class, matchId);

        if (match != null)
            Hibernate.initialize(match.getUsers());

        commit();
        close();
        return match;
    } catch (HibernateException e) {
        rollback();
        close();
        throw e;
    }
}

然后我打电话给泽西岛网络服务：

   @GET
@Path ("getMatch/{matchId}")
@Produces (MediaType.APPLICATION_JSON)
public Response getMatchById  (@PathParam ("matchId")long matchId)
{
    MatchDAO matchDAO = DAO.getInstance(MatchDAO.class);
    Matchs match = matchDAO.findMatchWithUsers(matchId);

    if (match != null)
        return Response.ok()
                       .entity(new GsonBuilder().setPrettyPrinting().create().toJson(match))
                       .build();

    return Response.status(Status.NOT_FOUND).entity("Match was not located").build();
}

但这引发了以下异常：

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.kyrogaming.models.Users.matchs, could not initialize proxy - no Session
at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:566)
at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:186)
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.PersistentBag.iterator(PersistentBag.java:266)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:95)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:60)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:89)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:195)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:96)
at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.write(CollectionTypeAdapterFactory.java:60)
at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.write(TypeAdapterRuntimeTypeWrapper.java:68)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.write(ReflectiveTypeAdapterFactory.java:89)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.write(ReflectiveTypeAdapterFactory.java:195)
at com.google.gson.Gson.toJson(Gson.java:593)
at com.google.gson.Gson.toJson(Gson.java:572)
at com.google.gson.Gson.toJson(Gson.java:527)
at com.google.gson.Gson.toJson(Gson.java:507)
at com.kyrogaming.services.MatchService.getMatchById(MatchService.java:77)
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:601)
at com.sun.jersey.spi.container.JavaMethodInvokerFactory$1.invoke(JavaMethodInvokerFactory.java:60)
at com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$ResponseOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:205)
at com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:75)
at com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:288)
at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
at com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:108)
at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
at com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:84)
at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1469)
at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1400)
at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1349)
at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1339)
at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416)
at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:537)
at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:699)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:565)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:479)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:119)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:521)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:227)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1031)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:406)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:186)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:965)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:117)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:111)
at org.eclipse.jetty.server.Server.handle(Server.java:349)
at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:449)
at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.headerComplete(AbstractHttpConnection.java:910)
at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:634)
at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:230)
at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:76)
at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:609)
at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:45)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:599)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:534)

我哪里出错了，因为我真的不知道为什么用户代理对象没有初始化。

这是所有Hibernate DAO类扩展的Abstract类，包含与hibernate交互的方法。

public abstract class AbstractHibernate <T>{
private SessionFactory sessionFactory;

private Session session;

@Inject
public void setSessionFactory (SessionFactory sessionFactory)
{
    this.sessionFactory = sessionFactory;
}



protected Session getSession () 
{
    if (sessionFactory == null)
        throw new NullPointerException("SessionFactory null ");
    if (session == null)
    {
        session = sessionFactory.openSession();
        return session; 
    }
    return session;
}


public void begin ()
{
    getSession().beginTransaction();
}



public void commit () throws HibernateException
{
    getSession().getTransaction().commit();
}


public void rollback ()
{
    getSession().getTransaction().rollback();
}


protected void close ()
{
    if (getSession () != null)
    {
        session.close();
        session = null;
    }
}

Answer 1

我认为.entity(new GsonBuilder().setPrettyPrinting().create().toJson(match))中的代码正在调用User.getMatchs()，但由于您已关闭会话，因此无法延迟加载它们。您应该在关闭会话之前热切地加载它们或加载它们。