序列化期间不相关的 NullPointerException [英] An irrelevant NullPointerException during serialization
本文介绍了序列化期间不相关的 NullPointerException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
我使用序列化将模型的当前状态保存到文件中，并在几分钟后加载它.我的应用程序没有涉及 JPA 或类似技术的内容.它是一个完全 JavaSE 桌面 Swing 应用程序.序列化工作得很好.只有我遇到在序列化后，我为 JList 定义的 DnD 功能停止运行(DnD 功能由我定义，不是默认功能).我不序列化 GUI.我只是序列化并保存模型.每次程序运行时都会创建 GUI.
I use serialization for saving the current state of my model to a file and load it maybe some minutes later. My application has nothing that deals JPA or similar technologies. It's a completely JavaSE desktop Swing Application. Serialization works quite well. Only I encountered that after the serialization the DnD feature that I have defined for a JList to another one stops to function(The DnD feature is defined by me and isn't a default one). I don't serialize the GUI. I just serialize and save the models. The GUI is created every time the program is run.
但曾几何时我发现发生了以下异常并且模型未序列化.这个异常只发生过一次.我可以在此之前保存序列化模型.(我注意到代码中没有发生任何变化)它在我的代码中没有任何线索.抛出此异常的代码行是:
But once upon a time I discovered that the following exception occurs and the model isn't serialized. This exception happened only once. I could save the serialized model before that.(I note that no change happened in the code) It doesn't have a clue in my code. The line of the code where this exception is thrown is:
out.writeObject(galMachine);
我知道错误太模糊了，但我很感激任何线索.谢谢！
I know that the error is so obscure but I appreciate any clue. Thanks!
顺便说一句，galMachine 不为空.该程序运行良好，因此其所有成员都已正确初始化！
Btw, the galMachine isn't null. The program works well so all its members have been initialized correctly!
注意:只有当我将序列化实例加载到程序中时才会发生此异常，而不是在它自己创建所有对象时发生.
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.plaf.metal.MetalScrollBarUI.installDefaults(MetalScrollBarUI.java:90)
at javax.swing.plaf.basic.BasicScrollBarUI.installUI(BasicScrollBarUI.java:168)
at javax.swing.JScrollBar.writeObject(JScrollBar.java:771)
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 java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:975)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1480)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1362)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1170)
at java.io.ObjectOutputStream.access$300(ObjectOutputStream.java:161)
at java.io.ObjectOutputStream$PutFieldImpl.writeFields(ObjectOutputStream.java:1687)
at java.io.ObjectOutputStream.writeFields(ObjectOutputStream.java:478)
at java.awt.Container.writeObject(Container.java:3681)
at sun.reflect.GeneratedMethodAccessor23.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:975)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1480)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1362)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1170)
at java.io.ObjectOutputStream.access$300(ObjectOutputStream.java:161)
at java.io.ObjectOutputStream$PutFieldImpl.writeFields(ObjectOutputStream.java:1687)
at java.io.ObjectOutputStream.writeFields(ObjectOutputStream.java:478)
at java.awt.Container.writeObject(Container.java:3681)
at sun.reflect.GeneratedMethodAccessor23.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:975)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1480)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1528)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
at java.util.ArrayList.writeObject(ArrayList.java:710)
at sun.reflect.GeneratedMethodAccessor19.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:975)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1480)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1528)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
at View.AppJFrame.saveMenuItemActionPerformed(AppJFrame.java:430)
at View.AppJFrame.access$500(AppJFrame.java:51)
at View.AppJFrame$4.actionPerformed(AppJFrame.java:307)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.AbstractButton.doClick(AbstractButton.java:376)
at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:833)
at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:877)
at java.awt.Component.processMouseEvent(Component.java:6505)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6270)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4861)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:723)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:682)
at java.awt.EventQueue$3.run(EventQueue.java:680)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:696)
at java.awt.EventQueue$4.run(EventQueue.java:694)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:693)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:244)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:139)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)
我使用 Java 1.7 和一个 GUI，主要是用 Netbeans 7.2 GUI 构建器创建的.我在应用程序中没有 Netbeans 特定功能，第一行是指 Java 代码中以下方法的第一行:
I'm using Java 1.7 with a GUI mostly created with Netbeans 7.2 GUI builder. I've got no Netbeans specific feature in the application and the first line refers to the first line of the following method in the Java codes:
protected void installDefaults() {
scrollBarWidth = ((Integer)(UIManager.get( "ScrollBar.width" ))).intValue();
super.installDefaults();
bumps = new MetalBumps( 10, 10, thumbHighlightColor, thumbShadow, thumbColor );
}
我再次注意到我没有兴趣保存 GUI，并且我的模型(galMachine)中没有任何 GUI 对象的引用.直接用于 GUI 的所有重要内容是两个 AbstractListModel 对象，它们不引用它们的 JList 组件.我只序列化galMachine.
I note again that I have no interest to save the GUI and I have no reference in my model(galMachine) to any GUI object. All important things directly for the GUI are two AbstractListModel objects that have no reference to their JList components. I only serialize the galMachine.
我发现在覆盖的 importData 方法中的 dragDrop 上也可能发生类似的异常.它发生在 try 后的第一行
I discovered that a similar exception could occur also on dragDrop inside the overriden importData method. It occurs at the first line after try
try {
Object obj = ts.getTransferable().getTransferData(TransferableProductJob.PRODUCTJOB_DATA_FLAVOR);
if(obj instanceof ProductJob){
ProductJob pj = (ProductJob) obj;
JList.DropLocation dl = (JList.DropLocation) ts.getDropLocation();
int idx = dl.getIndex();
StoreTank tank = ((StoreTank) jl.getModel().getElementAt(idx));
if(tank.getCurrentJobStage() != null){
JOptionPane.showMessageDialog(null,"\"" + tank.getDescription() + "\" è occupato.");
return false;
}
tank.setReserved(true);
tank.setReserved(false);
return false;
int initialTankNumber = tank.getNumber();
pj.importToStroreTank(initialTankNumber);
galvanicMachine.addJob(pj);
pj.start();
}
} catch (UnsupportedFlavorException ex) {
Logger.getLogger(WaitingListJPanel.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(WaitingListJPanel.class.getName()).log(Level.SEVERE, null, ex);
} catch (Exception ex ){
Logger.getLogger(WaitingListJPanel.class.getName()).log(Level.SEVERE, null, ex);
}
java.lang.NullPointerException
at javax.swing.plaf.metal.MetalScrollBarUI.installDefaults(MetalScrollBarUI.java:90)
at javax.swing.plaf.basic.BasicScrollBarUI.installUI(BasicScrollBarUI.java:168)
at javax.swing.JScrollBar.writeObject(JScrollBar.java:771)
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 java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:975)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1480)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1362)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1170)
at java.io.ObjectOutputStream.access$300(ObjectOutputStream.java:161)
at java.io.ObjectOutputStream$PutFieldImpl.writeFields(ObjectOutputStream.java:1687)
at java.io.ObjectOutputStream.writeFields(ObjectOutputStream.java:478)
at java.awt.Container.writeObject(Container.java:3681)
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 java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:975)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1480)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1362)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1170)
at java.io.ObjectOutputStream.access$300(ObjectOutputStream.java:161)
at java.io.ObjectOutputStream$PutFieldImpl.writeFields(ObjectOutputStream.java:1687)
at java.io.ObjectOutputStream.writeFields(ObjectOutputStream.java:478)
at java.awt.Container.writeObject(Container.java:3681)
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 java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:975)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1480)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1528)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
at java.util.ArrayList.writeObject(ArrayList.java:710)
at sun.reflect.GeneratedMethodAccessor12.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:975)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1480)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1528)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1528)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
at sun.awt.datatransfer.TransferableProxy.getTransferData(TransferableProxy.java:83)
at java.awt.dnd.DropTargetContext$TransferableProxy.getTransferData(DropTargetContext.java:376)
at View.panels.WaitingListJPanel$JListTransferHandler.importData(WaitingListJPanel.java:240)
at javax.swing.TransferHandler$DropHandler.drop(TransferHandler.java:1536)
at java.awt.dnd.DropTarget.drop(DropTarget.java:450)
at javax.swing.TransferHandler$SwingDropTarget.drop(TransferHandler.java:1274)
at sun.awt.dnd.SunDropTargetContextPeer.processDropMessage(SunDropTargetContextPeer.java:537)
at sun.awt.dnd.SunDropTargetContextPeer$EventDispatcher.dispatchDropEvent(SunDropTargetContextPeer.java:851)
at sun.awt.dnd.SunDropTargetContextPeer$EventDispatcher.dispatchEvent(SunDropTargetContextPeer.java:775)
at sun.awt.dnd.SunDropTargetEvent.dispatch(SunDropTargetEvent.java:48)
at java.awt.Component.dispatchEventImpl(Component.java:4716)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processDropTargetEvent(Container.java:4566)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4417)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4687)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:723)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:682)
at java.awt.EventQueue$3.run(EventQueue.java:680)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:696)
at java.awt.EventQueue$4.run(EventQueue.java:694)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:693)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:244)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:139)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)
<小时>
我在互联网上搜索，发现这样的错误曾经发生过，并且之前仅作为错误宣布过一次，但已作为错误被拒绝.这是错误报告.但它不能在我的代码中，因为我不会尝试同时在两个线程中初始化两个 JScrollPane 但我希望它有助于提出解决方案.
I searched the Internet and I discovered such this error has happened and announced as a bug only once before and has been rejected as a bug. This is the bug report. But it can't be in my code because I don't try to initialize two JScrollPane in two threads simultaneously but I hope that it will help for suggesting a solution.
推荐答案
我找到了一个非常痛苦的补救方法.它应该是Java中的一个错误.当我将 lookAndFeel 从 nimbus 更改为系统默认值或 metal 时，问题就消失了.所以这是Java中的一个错误！:(
I found a quite painful remedy. It should be a bug in Java. When I change the lookAndFeel from nimbus to the system default or metal the problem disappears. So it is a bug in Java! :(
UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel");
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