Exception.getCause()在尝试查找异常源时返回null [英] Exception.getCause() returning null when trying to find the source of an exception
问题描述
为什么 System.out.println(e.getCause());
给出 null
?
并且可以像这样存储整个HashSet集合吗?
why does System.out.println(e.getCause());
gives null
?
And can store whole HashSet collection like this?
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)
仍然没有看到问题,除了它在第一个收集对象上占据了一席之地,并且集合正在实现 Serializable
,所有对象也实现 Serializable
并且线程具有瞬态声明
Still do not see the problem, except that it snaped on first object of collection, and collection is implementing Serializable
, all objects also implement Serializable
and threads have transient where declared
推荐答案
当链接异常时, getCause
方法用于获取原始原因。在这种情况下,异常没有从任何其他层链接,因此 getCause
返回 null
。您应该使用 e.printStackTrace()
来获取异常的原因。最有可能的原因是, HashSet
中的一个或多个键/值属于未实现 java.io.Serializable的类型
。
When an exception is chained, the getCause
method is used to get the original cause. In this case, the exception was not chained from any other layer, hence getCause
returns null
. You should use e.printStackTrace()
instead, to get the reason for the exception. Most likely, this would be because one or more keys/values in your HashSet
are of a type that is not implementing java.io.Serializable
.
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