如何修复"LazyInitializationException"?我遇到了吗? [英] How to fix the "LazyInitializationException" i'm encountering?

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本文介绍了如何修复"LazyInitializationException"?我遇到了吗?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

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之后，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...

我试图强制Eager加载而不是延迟加载，但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)

这是一个示例，说明如何尝试在数据库中检索图片(只有这两个具有外键)

@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发生异常 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. 预先谢谢你.

丢失的开发人员.

解决方案

让我们一步一步地将其划分

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，这将导致异常.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)您不应该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;
}

Hope you'll be able to help me stop hitting my head against a wall.

Here's my problem, after plenty days of research on many forums, I didn't found any compatible answer with the problem i'm encountering.

I have the org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.supinfo.suppicture.entity.User.pictures, no session or session was closed that seems to be a known Exception, but still drives me crazy...

I've tried to force Eager loading instead of lazy loading but still having the same issue.

Here is my classes :

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)

And here is an example of how I try to retrieve my pictures in database (wich is the only one that have foreign keys)

@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();
    }
}

Finally called like this : 

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

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

Full stacktrace of exception bellow :

févr. 03, 2019 4:38:48 PM org.hibernate.LazyInitializationException GRAVE: failed to lazily initialize a collection of role: com.supinfo.suppicture.entity.User.pictures, no session or session was closed org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.supinfo.suppicture.entity.User.pictures, no session or session was closed at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:383) at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:375) at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:368) at org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:111) at org.hibernate.collection.PersistentBag.iterator(PersistentBag.java:272) at com.sun.xml.internal.bind.v2.runtime.reflect.Lister$CollectionLister.iterator(Lister.java:266) at com.sun.xml.internal.bind.v2.runtime.reflect.Lister$CollectionLister.iterator(Lister.java:253) at com.sun.xml.internal.bind.v2.runtime.property.ArrayElementProperty.serializeListBody(ArrayElementProperty.java:118) at com.sun.xml.internal.bind.v2.runtime.property.ArrayERProperty.serializeBody(ArrayERProperty.java:144) at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:345) at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:681) at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody(SingleElementNodeProperty.java:143) at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:345) at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsSoleContent(XMLSerializer.java:578) at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeRoot(ClassBeanInfoImpl.java:326) at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsRoot(XMLSerializer.java:479) at com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:308) at com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.marshal(MarshallerImpl.java:163) at com.sun.jersey.json.impl.provider.entity.JSONListElementProvider.writeList(JSONListElementProvider.java:145) at com.sun.jersey.core.provider.jaxb.AbstractListElementProvider.writeTo(AbstractListElementProvider.java:264) at com.sun.jersey.spi.container.ContainerResponse.write(ContainerResponse.java:306) at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1448) at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1360) at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1350) at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416) at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:538) at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:716) at javax.servlet.http.HttpServlet.service(HttpServlet.java:725) 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.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:506) 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:610) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:537) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1081) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:658) at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:222) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1566) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1523) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:748)

févr. 03, 2019 4:38:48 PM org.apache.catalina.core.StandardWrapperValve invoke GRAVE: "Servlet.service()" pour la servlet jersey-servlet a généré une exception org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.supinfo.suppicture.entity.User.pictures, no session or session was closed at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:383) at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:375) at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:368) at org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:111) at org.hibernate.collection.PersistentBag.iterator(PersistentBag.java:272) at com.sun.xml.internal.bind.v2.runtime.reflect.Lister$CollectionLister.iterator(Lister.java:266) at com.sun.xml.internal.bind.v2.runtime.reflect.Lister$CollectionLister.iterator(Lister.java:253) at com.sun.xml.internal.bind.v2.runtime.property.ArrayElementProperty.serializeListBody(ArrayElementProperty.java:118) at com.sun.xml.internal.bind.v2.runtime.property.ArrayERProperty.serializeBody(ArrayERProperty.java:144) at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:345) at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsXsiType(XMLSerializer.java:681) at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.serializeBody(SingleElementNodeProperty.java:143) at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeBody(ClassBeanInfoImpl.java:345) at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsSoleContent(XMLSerializer.java:578) at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.serializeRoot(ClassBeanInfoImpl.java:326) at com.sun.xml.internal.bind.v2.runtime.XMLSerializer.childAsRoot(XMLSerializer.java:479) at com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.write(MarshallerImpl.java:308) at com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.marshal(MarshallerImpl.java:163) at com.sun.jersey.json.impl.provider.entity.JSONListElementProvider.writeList(JSONListElementProvider.java:145) at com.sun.jersey.core.provider.jaxb.AbstractListElementProvider.writeTo(AbstractListElementProvider.java:264) at com.sun.jersey.spi.container.ContainerResponse.write(ContainerResponse.java:306) at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1448) at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1360) at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1350) at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416) at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:538) at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:716) at javax.servlet.http.HttpServlet.service(HttpServlet.java:725) 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.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:506) 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:610) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:537) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1081) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:658) at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:222) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1566) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1523) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:748)

Please tell me if you need more of my code to help me solve the problem. Thank you in advance.`

A lost developer.

解决方案

Let divide this step by step

1) Your jersey web controller is calling your dao method to get list of pictures (No error)

2) Now your dao layer is getting data from database (No error)

3) Value is returned to your web service controller method (No error)

4) But you are using automatic json converter to convert object data to json. Your pictures has data associated with user. When json converter tries to get data of user the value is null because your transaction has already ended which is resulting in exception. Try ignoring category and user fields during json conversion as shown below.

@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) You should not use the picture object directly for json conversion as it will result in cyclic redundancy (infinite loop). Try to create another wrapper class of picture to handle this scenario

Picture -> User -> Picture -> User (Cyclic redundancy)

So for fixing this create three wrapper classes

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;
}

Then change getAllPictures method to following 

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;
}

这篇关于如何修复"LazyInitializationException"?我遇到了吗?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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