Exception.getCause() returning null when trying to find the source of an exception

Question

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();
    }
}

Used printStackTrace() instead of 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)

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

There are cases where both getCause() and getMessage() will be null. The only good solution is to understand what exception types are going to be thrown and handle them gracefully. — Shanerk, Apr 23 '18 at 15:08

Binil Thomas · Answer 1 · 2011-05-28T00:31:15.370

14

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.

edited May 28 '11 at 00:31

answered May 28 '11 at 00:23

Binil Thomas

13,699
10
57
70

score 0 · Answer 2 · answered Aug 28 '19 at 13:57

0

Below code gave me exact cause of the exception

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(); 
}

answered Aug 28 '19 at 13:57

dilipkumar katre

128
1
12

1

This doesn't seem to answer the question - though it does help with further debugging – Rastalamm Aug 28 '19 at 14:18

score 0 · Answer 3 · answered May 28 '11 at 00:27

0

Use printStackTrace() instead of getCause().

And yes, you can save a whole collection (as long as it holds objects that implement Serilizable).

answered May 28 '11 at 00:27

Iñigo Beitia

6,303
4
40
46

When dealing with an exception mostly you can use printStackTrace() or getMessage() for simple exception message. In your whole Collection, all class inside should implements Serializable interface – Ali Irawan May 28 '11 at 01:02

score 0 · Answer 4 · answered Jun 30 '22 at 05:47

You can use this method to get cause.

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();
    }
}

Exception.getCause() returning null when trying to find the source of an exception

4 Answers4

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