Question

希望您能够帮助我停止将我的头撞在墙上。

这是我的问题，在许多论坛上进行了大量研究后，我没有找到与我遇到的问题兼容的答案。

我有一个org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.supinfo.suppicture.entity.User.pictures, no session or session was closed似乎是一个已知的异常，但仍然让我发疯...

我尝试强制Eager加载而不是延迟加载，但是仍然存在相同的问题。

这是我的课程：

category.java

@Entity
@Table(name = "category")
@XmlRootElement
public class Category{

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private int id;

private String Name;

@OneToMany(mappedBy = "category")
private Collection<Picture> pictures;

(getters and setters)

user.java

@Entity
@Table(name = "user")
@XmlRootElement
public class User {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private int id;

private String username;

private String password;

private String firstName;

private String lastName;

private String phoneNumber;

private String postalAddress;

private String email;

@OneToMany(mappedBy = "author")
private Collection<Picture> pictures;

    (getters and setters)

picture.java

@Entity
@Table(name = "picture")
@XmlRootElement
public class Picture {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private int id;

private String name;

private String description;

@Column(columnDefinition="longblob")
private byte[] image;

private Date dateOfPublish;

@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "category_id")
private Category category;

@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "user_id")
private User author;

    (getters and setters)

这是我如何尝试在数据库中检索图片的示例（其中只有唯一一个具有外键的图片）

@Override
public List<Picture> getAllPictures() {
    EntityManager em = emf.createEntityManager();
    try {
        CriteriaQuery<Picture> criteriaQuery = em.getCriteriaBuilder()
            .createQuery(Picture.class);
        criteriaQuery.from(Picture.class);
        return em.createQuery(criteriaQuery).getResultList();
    } finally {
        em.close();
    }
}

最后这样称呼：

@Path("/picture")
public class PictureController {

@GET
@Path("/all") @Produces(MediaType.APPLICATION_JSON)
public List<Picture> getAllPictures(){
    return DaoFactory.getPictureDao().getAllPictures();
}

下面是异常的完整堆栈跟踪：

févr。 2019年3月3日4:38:48 org.hibernate.LazyInitializationException GRAVE：无法延迟初始化角色集合：com.supinfo.suppicture.entity.User.pictures，没有会话或会话被关闭 org.hibernate.LazyInitializationException：无法延迟初始化角色集合：com.supinfo.suppicture.entity.User.pictures，没有会话或会话被关闭在org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException（AbstractPersistentCollection.java:383）在org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected（AbstractPersistentCollection.java:375）在org.hibernate.collection.AbstractPersistentCollection.initialize（AbstractPersistentCollection.java:368）在org.hibernate.collection.AbstractPersistentCollection.read（AbstractPersistentCollection.java:111）在org.hibernate.collection.PersistentBag.iterator（PersistentBag.java:272）在com.sun.xml.internal.bind.v2.runtime.reflect.Lister $ CollectionLister.iterator（Lister.java:266）在com.sun.xml.internal.bind.v2.runtime.reflect.Lister $ CollectionLister.iterator（Lister.java:253）在com.sun.xml.internal.bind.v2.runtime.property.ArrayElementProperty.serializeListBody（ArrayElementProperty.java:118）在com.sun.xml.internal.bind.v2.runtime.property.ArrayERProperty.serializeBody（ArrayERProperty.java:144）在com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody（ClassBeanInfoImpl.java:345）在com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType（XMLSerializer.java:681）在com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody（SingleElementNodeProperty.java:143）在com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody（ClassBeanInfoImpl.java:345）在com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsSoleContent（XMLSerializer.java:578）在com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeRoot（ClassBeanInfoImpl.java:326）在com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsRoot（XMLSerializer.java:479）在com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.write（MarshallerImpl.java:308）在com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.marshal（MarshallerImpl.java:163）在com.sun.jersey.json.impl.provider.entity.JSONListElementProvider.writeList（JSONListElementProvider.java:145）在com.sun.jersey.core.provider.jaxb.AbstractListElementProvider.writeTo（AbstractListElementProvider.java:264）在com.sun.jersey.spi.container.ContainerResponse.write（ContainerResponse.java:306）在com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest（WebApplicationImpl.java:1448）在com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest（WebApplicationImpl.java:1360）在com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest（WebApplicationImpl.java:1350）在com.sun.jersey.spi.container.servlet.WebComponent.service（WebComponent.java:416）在com.sun.jersey.spi.container.servlet.ServletContainer.service（ServletContainer.java:538）在com.sun.jersey.spi.container.servlet.ServletContainer.service（ServletContainer.java:716）在javax.servlet.http.HttpServlet.service（HttpServlet.java:725）在org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:291）在org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:206）在org.apache.tomcat.websocket.server.WsFilter.doFilter（WsFilter.java:52）在org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:239）在org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:206）在org.apache.catalina.core.StandardWrapperValve.invoke（StandardWrapperValve.java:219）在org.apache.catalina.core.StandardContextValve.invoke（StandardContextValve.java:106）在org.apache.catalina.authenticator.AuthenticatorBase.invoke（AuthenticatorBase.java:506）在org.apache.catalina.core.StandardHostValve.invoke（StandardHostValve.java:142）在org.apache.catalina.valves.ErrorReportValve.invoke（ErrorReportValve.java:79）在org.apache.catalina.valves.AbstractAccessLogValve.invoke（AbstractAccessLogValve.java:610）在org.apache.catalina.core.StandardEngineValve.invoke（StandardEngineValve.java:88）在org.apache.catalina.connector.CoyoteAdapter.service（CoyoteAdapter.java:537）在org.apache.coyote.http11.AbstractHttp11Processor.process（AbstractHttp11Processor.java:1081）在org.apache.coyote.AbstractProtocol $ AbstractConnectionHandler.process（AbstractProtocol.java:658）在org.apache.coyote.http11.Http11NioProtocol $ Http11ConnectionHandler.process（Http11NioProtocol.java:222）在org.apache.tomcat.util.net.NioEndpoint $ SocketProcessor.doRun（NioEndpoint.java:1566）在org.apache.tomcat.util.net.NioEndpoint $ SocketProcessor.run（NioEndpoint.java:1523）在java.util.concurrent.ThreadPoolExecutor.runWorker（ThreadPoolExecutor.java:1149）在java.util.concurrent.ThreadPoolExecutor $ Worker.run（ThreadPoolExecutor.java:624）在org.apache.tomcat.util.threads.TaskThread $ WrappingRunnable.run（TaskThread.java:61）在java.lang.Thread.run（Thread.java:748）

févr。 2019年03月3日4:38:48 org.apache.catalina.core.StandardWrapperValve调用严重：“ Servlet.service（）”注入servlet球衣-servlet一般情况 org.hibernate.LazyInitializationException：无法延迟初始化角色集合：com.supinfo.suppicture.entity.User.pictures，没有会话或会话被关闭在org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException（AbstractPersistentCollection.java:383）在org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected（AbstractPersistentCollection.java:375）在org.hibernate.collection.AbstractPersistentCollection.initialize（AbstractPersistentCollection.java:368）在org.hibernate.collection.AbstractPersistentCollection.read（AbstractPersistentCollection.java:111）在org.hibernate.collection.PersistentBag.iterator（PersistentBag.java:272）在com.sun.xml.internal.bind.v2.runtime.reflect.Lister $ CollectionLister.iterator（Lister.java:266）在com.sun.xml.internal.bind.v2.runtime.reflect.Lister $ CollectionLister.iterator（Lister.java:253）在com.sun.xml.internal.bind.v2.runtime.property.ArrayElementProperty.serializeListBody（ArrayElementProperty.java:118）在com.sun.xml.internal.bind.v2.runtime.property.ArrayERProperty.serializeBody（ArrayERProperty.java:144）在com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody（ClassBeanInfoImpl.java:345）在com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType（XMLSerializer.java:681）在com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody（SingleElementNodeProperty.java:143）在com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody（ClassBeanInfoImpl.java:345）在com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsSoleContent（XMLSerializer.java:578）在com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeRoot（ClassBeanInfoImpl.java:326）在com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsRoot（XMLSerializer.java:479）在com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.write（MarshallerImpl.java:308）在com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.marshal（MarshallerImpl.java:163）在com.sun.jersey.json.impl.provider.entity.JSONListElementProvider.writeList（JSONListElementProvider.java:145）在com.sun.jersey.core.provider.jaxb.AbstractListElementProvider.writeTo（AbstractListElementProvider.java:264）在com.sun.jersey.spi.container.ContainerResponse.write（ContainerResponse.java:306）在com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest（WebApplicationImpl.java:1448）在com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest（WebApplicationImpl.java:1360）在com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest（WebApplicationImpl.java:1350）在com.sun.jersey.spi.container.servlet.WebComponent.service（WebComponent.java:416）在com.sun.jersey.spi.container.servlet.ServletContainer.service（ServletContainer.java:538）在com.sun.jersey.spi.container.servlet.ServletContainer.service（ServletContainer.java:716）在javax.servlet.http.HttpServlet.service（HttpServlet.java:725）在org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:291）在org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:206）在org.apache.tomcat.websocket.server.WsFilter.doFilter（WsFilter.java:52）在org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:239）在org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:206）在org.apache.catalina.core.StandardWrapperValve.invoke（StandardWrapperValve.java:219）在org.apache.catalina.core.StandardContextValve.invoke（StandardContextValve.java:106）在org.apache.catalina.authenticator.AuthenticatorBase.invoke（AuthenticatorBase.java:506）在org.apache.catalina.core.StandardHostValve.invoke（StandardHostValve.java:142）在org.apache.catalina.valves.ErrorReportValve.invoke（ErrorReportValve.java:79）在org.apache.catalina.valves.AbstractAccessLogValve.invoke（AbstractAccessLogValve.java:610）在org.apache.catalina.core.StandardEngineValve.invoke（StandardEngineValve.java:88）在org.apache.catalina.connector.CoyoteAdapter.service（CoyoteAdapter.java:537）在org.apache.coyote.http11.AbstractHttp11Processor.process（AbstractHttp11Processor.java:1081）在org.apache.coyote.AbstractProtocol $ AbstractConnectionHandler.process（AbstractProtocol.java:658）在org.apache.coyote.http11.Http11NioProtocol $ Http11ConnectionHandler.process（Http11NioProtocol.java:222）在org.apache.tomcat.util.net.NioEndpoint $ SocketProcessor.doRun（NioEndpoint.java:1566）在org.apache.tomcat.util.net.NioEndpoint $ SocketProcessor.run（NioEndpoint.java:1523）在java.util.concurrent.ThreadPoolExecutor.runWorker（ThreadPoolExecutor.java:1149）在java.util.concurrent.ThreadPoolExecutor $ Worker.run（ThreadPoolExecutor.java:624）在org.apache.tomcat.util.threads.TaskThread $ WrappingRunnable.run（TaskThread.java:61）在java.lang.Thread.run（Thread.java:748）

请告诉我您是否需要更多我的代码来帮助我解决问题。谢谢你。

丢失的开发人员。

Answer 1

似乎没有打开会话，也没有事务。您缺少交易的开始和结束。
有两种选择，要么是您自己的经理自己进行交易，要么是某个事务经理在某个容器中进行交易。
非托管环境习惯用法

EntityManager em = emf.createEntityManager（）; EntityTransaction tx = null; 尝试{ tx = em.getTransaction（）; tx.begin（）;

//做一些工作 ... 在此处输入代码 tx.commit（）; } catch（RuntimeException e）{ 如果（tx！= null && tx.isActive（）） tx.rollback（）; 抛出e; //或显示错误消息 } 最后{ em.close（）; }
此处有更多信息：https://docs.jboss.org/hibernate/orm/4.0/hem/en-US/html/transactions.html

Answer 2

让我们分步进行

1）您的jersey网络控制器正在调用dao方法以获取图片列表（无错误）

2）现在您的dao层正在从数据库中获取数据（无错误）

3）值返回到您的Web服务控制器方法（无错误）

4）但是您正在使用自动json转换器将对象数据转换为json。您的图片具有与用户关联的数据。当json转换器尝试获取用户数据时，该值为null，因为您的事务已经结束，从而导致异常。尝试在json转换过程中忽略类别和用户字段，如下所示。

@JsonIgnore
@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "category_id")
private Category category;

@JsonIgnore
@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "user_id")
private User author;

5）您不应将图片对象直接用于json转换，因为它会导致循环冗余（无限循环）。尝试创建另一个图片包装类来处理这种情况

图片->用户->图片->用户（循环冗余）

为解决此问题，请创建三个包装器类

public class PictureWrapper 
{
    private int id;

    private String name;

    private String description;

    private byte[] image;

    private Date dateOfPublish;

    private CategoryWrapper category;

    private UserWrapper author;
}


public class UserWrapper
{
    private int id;

    private String username;

    private String password;

    private String firstName;

    private String lastName;

    private String phoneNumber;

    private String postalAddress;

    private String email;
}

public class CategoryWrapper
{
    private int id;

    private String Name;
}

然后将getAllPictures方法更改为

public List<PictureWrapper> getAllPictures() 
{
    List<PictureWrapper> resultList = new ArrayList<PictureWrapper>();
    EntityManager em = emf.createEntityManager();
    try 
    {
        CriteriaQuery<Picture> criteriaQuery = em.getCriteriaBuilder().createQuery(Picture.class);
        criteriaQuery.from(Picture.class);
        List<Picture> list =  em.createQuery(criteriaQuery).getResultList();
    if(list != null && list.size() != 0)
    {
        for(Picture picture : list)
        {
            PictureWrapper pictureWrapper = new PictureWrapper();
            //Load data from picture to picture wrapper with user and category
            resultList.add(pictureWrapper);
        }
    }
    } 
    finally 
    {
        em.close();
    }
    return resultList;
}

Answer 3

您需要使用获取策略OneToMany装饰user.pictures属性category.pictures和EAGER。

class Category {
    @OneToMany(mappedBy = "category", fetch = FetchType.EAGER)
    Collection<Picture> pictures;
}

class User {
    @OneToMany(mappedBy = "author", fetch = FetchType.EAGER)
    Collection<Picture> pictures;
}

请注意，实际上，您不需要使用ManyToOne获取策略来装饰EAGER属性，因为这被视为默认行为。

Answer 4

感谢Santosh Balaji的把戏;）

如何解决我遇到的“ LazyInitializationException”问题？

4 个答案: