使用hibernate和gilead for gwt添加到实体类中保存的列表时的LazyInitializationException
是的，所以我正在使用hibernate gilead和gwt将我的数据保存在网站的用户和文件中。 我的用户有一个文件位置列表。 我正在使用注释将我的类映射到数据库。 当我尝试将文件位置添加到用户类中保存的列表时，我得到一个org.hibernate.LazyInitializationException 。
这是一个从我正在使用的外部文件上传servlet类重写的方法。 当文件上传时，它调用此方法。
user1从其他地方的数据库加载。 user1.getFileLocations().add(fileLocation);发生exceptionuser1.getFileLocations().add(fileLocation); 。 我根本不明白它。 任何帮助都会很棒。 错误的堆栈跟踪如下
public String executeAction(HttpServletRequest request, List sessionFiles) throws UploadActionException { for (FileItem item : sessionFiles) { if (false == item.isFormField()) { try { YFUser user1 = (YFUser)getSession().getAttribute(SESSION_USER); // This is the location where a file will be stored String fileLocationString = "/Users/Stefano/Desktop/UploadedFiles/" + user1.getUsername(); File fl = new File(fileLocationString); fl.mkdir(); // so here i will create the a file container for my uploaded file File file = File.createTempFile("upload-", ".bin",fl); // this is where the file is written to disk item.write(file); // the FileLocation object is then created FileLocation fileLocation = new FileLocation(); fileLocation.setLocation(fileLocationString); //test System.out.println("file path = "+file.getPath()); user1.getFileLocations().add(fileLocation); //the line above is where the exception occurs } catch (Exception e) { throw new UploadActionException(e.getMessage()); } } removeSessionFileItems(request); } return null; }
//这是您的文件用户的类文件
@Entity @Table(name = "yf_user_table") public class YFUser implements Serializable,ILightEntity { @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "user_id",nullable = false) private int userId; @Column(name = "username") private String username; @Column(name = "password") private String password; @Column(name = "email") private String email; @ManyToMany(cascade = CascadeType.ALL) @JoinTable(name = "USER_FILELOCATION", joinColumns = { @JoinColumn(name = "user_id") }, inverseJoinColumns = { @JoinColumn(name = "locationId") }) private List fileLocations = new ArrayList() ; public YFUser(){ } public int getUserId() { return userId; } private void setUserId(int userId) { this.userId = userId; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public List getFileLocations() { if(fileLocations ==null){ fileLocations = new ArrayList(); } return fileLocations; } public void setFileLocations(List fileLocations) { this.fileLocations = fileLocations; } /* public void addFileLocation(FileLocation location){ fileLocations.add(location); }*/ @Override public void addProxyInformation(String property, Object proxyInfo) { // TODO Auto-generated method stub } @Override public String getDebugString() { // TODO Auto-generated method stub return null; } @Override public Object getProxyInformation(String property) { // TODO Auto-generated method stub return null; } @Override public boolean isInitialized(String property) { // TODO Auto-generated method stub return false; } @Override public void removeProxyInformation(String property) { // TODO Auto-generated method stub } @Override public void setInitialized(String property, boolean initialised) { // TODO Auto-generated method stub } @Override public Object getValue() { // TODO Auto-generated method stub return null; }
}
@Entity @Table(name = "fileLocationTable") public class FileLocation implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "locationId", updatable = false, nullable = false) private int ieId; @Column (name = "location") private String location; public FileLocation(){ } public int getIeId() { return ieId; } private void setIeId(int ieId) { this.ieId = ieId; } public String getLocation() { return location; } public void setLocation(String location) { this.location = location; }
}
Apr 2, 2010 11:33:12 PM org.hibernate.LazyInitializationException SEVERE: failed to lazily initialize a collection of role: com.example.client.YFUser.fileLocations, no session or session was closed org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.example.client.YFUser.fileLocations, no session or session was closed at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:380) at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:372) at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:365) at org.hibernate.collection.AbstractPersistentCollection.write(AbstractPersistentCollection.java:205) at org.hibernate.collection.PersistentBag.add(PersistentBag.java:297) at com.example.server.TestServiceImpl.saveFileLocation(TestServiceImpl.java:132) 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 net.sf.gilead.gwt.PersistentRemoteService.processCall(PersistentRemoteService.java:174) at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:224) at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62) at javax.servlet.http.HttpServlet.service(HttpServlet.java:713) at javax.servlet.http.HttpServlet.service(HttpServlet.java:806) at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487) at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:362) at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181) at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:729) at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at org.mortbay.jetty.handler.RequestLogHandler.handle(RequestLogHandler.java:49) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at org.mortbay.jetty.Server.handle(Server.java:324) at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:505) at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:843) at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:647) at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:211) at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:380) at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:396) at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:488) Apr 2, 2010 11:33:12 PM net.sf.gilead.core.PersistentBeanManager clonePojo INFO: Third party instance, not cloned : org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.example.client.YFUser.fileLocations, no session or session was closed
Lazy意味着只有在访问它们时才从数据库加载集合的值。 如果此时Session已关闭，则抛出LazyInitializationException ，因为无法获取数据。
在您的情况下，我只是建议为关联添加一个急切的提取类型：
@ManyToMany(cascade = CascadeType.ALL, fetchType=FetchType.EAGER)
这将在加载实体时加载fileLocations ，并且不需要延迟加载。
一个常见的解决方案是使用OpenSessionInView ，但它可能并不总是与GWT一起使用，因为客户端是远程的，并且无法在那里打开会话。
因此，您将在延迟初始化时遇到一些问题。 你可以搜索相关的问题，有几个 – 例如这个和这个 。
此exception意味着尚未加载FileLocations关联，并且您尝试访问它。 没有打开会话，也无法加载关联。 这是LazyInitializationException。
编辑：阅读Bozho的解决方案post。