[英]Exception.getCause() returning null when trying to find the source of an exception
為什么System.out.println(e.getCause());
給出null
? 並且可以像這樣存儲整個 HashSet 集合嗎?
private void saving() throws IOException, ClassNotFoundException {
ObjectOutputStream out = null;
try {
out = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream(dataFile)));
out.writeObject(c);
} catch (java.io.NotSerializableException e) {
System.out.println(e.getCause());
} finally {
out.close();
}
}
使用printStackTrace()
而不是getCause()
java.io.NotSerializableException: Data$1
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1180)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1528)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
at java.util.HashSet.writeObject(HashSet.java:284)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:616)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:962)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1480)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
at Prozor.saving(Prozor.java:81)
at Prozor.actionPerformed(Prozor.java:57)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2012)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2335)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:404)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:253)
at java.awt.Component.processMouseEvent(Component.java:6268)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
at java.awt.Component.processEvent(Component.java:6033)
at java.awt.Container.processEvent(Container.java:2045)
at java.awt.Component.dispatchEventImpl(Component.java:4629)
at java.awt.Container.dispatchEventImpl(Container.java:2103)
at java.awt.Component.dispatchEvent(Component.java:4455)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4633)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4297)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4227)
at java.awt.Container.dispatchEventImpl(Container.java:2089)
at java.awt.Window.dispatchEventImpl(Window.java:2517)
at java.awt.Component.dispatchEvent(Component.java:4455)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:649)
at java.awt.EventQueue.access$000(EventQueue.java:96)
at java.awt.EventQueue$1.run(EventQueue.java:608)
at java.awt.EventQueue$1.run(EventQueue.java:606)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:105)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:116)
at java.awt.EventQueue$2.run(EventQueue.java:622)
at java.awt.EventQueue$2.run(EventQueue.java:620)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:105)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:619)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:275)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:200)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:190)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:185)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:177)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:138)
仍然沒有看到問題,除了它捕捉到集合的第一個 object ,並且集合正在實現Serializable
,所有對象也實現Serializable
並且線程在聲明的地方具有瞬態
當異常被鏈接時, getCause
方法用於獲取原始原因。 在這種情況下,異常沒有從任何其他層鏈接,因此getCause
返回null
。 您應該使用e.printStackTrace()
來獲取異常的原因。 這很可能是因為HashSet
中的一個或多個鍵/值屬於未實現java.io.Serializable
的類型。
下面的代碼給了我異常的確切原因
try{
// code
}
catch(Exception ex){
Exception exe = new Exception();
String causeString="";
exe.initCause(ex);
if(exe.getCause()!=null && exe.getCause().getCause()!=null)
causeString= exe.getCause().getCause().getLocalizedMessage();
}
使用printStackTrace()
而不是getCause()
。
是的,您可以保存整個集合(只要它包含實現 Serilizable 的對象)。
您可以使用此方法找到原因。
private void saving() throws IOException, ClassNotFoundException {
ObjectOutputStream out = null;
try {
out = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream(dataFile)));
out.writeObject(c);
} catch (java.io.NotSerializableException e) {
System.out.println(e.fillInStackTrace());
} finally {
out.close();
}
}
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