Java Exception Stacktrace Not Printing

Question

I have the following code:

import org.apache.commons.lang.exception.ExceptionUtils;
public void myMethod() {
    try {
        // do something
    } catch (Exception e) {
        System.out.println(ExceptionUtils.getStackTrace(e)); // prints "java.lang.NullPointerException"
        System.out.println(ExceptionUtils.getFullStackTrace(e)); // prints "java.lang.NullPointerException"
        e.printStackTrace(); // prints "java.lang.NullPointerException"
    }
}

The output that I would like to see is a full stacktrace with line numbers and the hierarchy of classes that failed. For example,

Exception in thread "main" java.lang.NullPointerException
        at org.Test.myMethod(Test.java:674)
        at org.TestRunner.anotherMethod(TestRunner.java:505)
        at java.util.ArrayList(ArrayList.java:405)

This code is being run inside a larger app which also has log4j, but I'm hoping to be able to get the exception into a string so I can send it as an email to the java developers.

Does anyone have any ideas about how I can capture the full stack trace to a string? I can't use Thread.currentThread().getStackTrace() since this app runs on Java 4. What might be blocking the above code from printing the full stacktrace?

Looks like the StackTraceElement array in NPE is being reset to empty. Is anything calling setStackTrace on the NPE? — Dan Gravell
– Dan Gravell, Commented Sep 11, 2012 at 14:41
Are you able to debug this in an IDE? Might be worth setting a breakpoint in the catch block to see if the Exception is 'perfectly formed'. — Dan Gravell
– Dan Gravell, Commented Sep 11, 2012 at 14:49
add the logged output of your myMethod() or your actual method. e.printStackTrace(); normally should print the fill trace. — basiljames
– basiljames, Commented Sep 11, 2012 at 14:53

2011 · Accepted Answer · 2013-03-08 13:50:45Z

18

this is beacause java does some code optimiziation when run in server mode (java -server) to skip this. use -XX:-OmitStackTraceInFastThrow in java args see link below for details:

http://jawspeak.com/2010/05/26/hotspot-caused-exceptions-to-lose-their-stack-traces-in-production-and-the-fix/

answered Mar 8, 2013 at 13:50

2011

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4 Comments

Sarel Botha Over a year ago

Instead of turning off this optimization on a production server I would just follow Peter's advice and look at an earlier error in the log.

2011 Over a year ago

I agree that can be done when you own the code, if you are dependenty on someone else, till they fix, this is the best you could do.

dpetruha Over a year ago

This is definitely what caused the similar problem for me on Prod. Thank you for the answer!

Champ Over a year ago

This exists on OpenJDK7 but not on OpenJDK8.

Peter Lawrey · Accepted Answer · 2012-09-11 14:55:20Z

14

If you repeatedly throw an exception, the JVM stop filling in the stack trace. I am not sure why but it may be to reduce load on the JVM. You need to be looking at an earlier stack trace to see the details.

for (int n = 0; ; n++) {
    try {
        Integer i = null;
        i.hashCode();
    } catch (Exception e) {
        if (e.getStackTrace().length == 0) {
            System.out.println("No more stack trace after " + n + " thrown.");
            break;
        }
    }

prints

No more stack trace after 20707 thrown.

answered Sep 11, 2012 at 14:55

Peter Lawrey

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Comments

JaskeyLam · Accepted Answer · 2014-08-07 05:14:50Z

4

Does anyone have any ideas about how I can capture the full stack trace to a string?

You can use the below way(StringWriter.toString()) to transfer the stack trace into a String.

 StringWriter writer = new StringWriter();
 e.printStackTrace( new PrintWriter(writer,true ));
 System. out.println("exeption stack is :\n"+writer.toString());

answered Aug 7, 2014 at 5:14

JaskeyLam

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Comments

basiljames · Accepted Answer · 2012-09-11 15:01:25Z

2

The exception might be caught and thrown somewhere before your catch block. Maybe in another class which your are calling to do the logic.

An Exception created like
new Exception(new Throwable("java.lang.NullPointerException"));
will print something like what you see.

edited Sep 11, 2012 at 15:01

answered Sep 11, 2012 at 14:55

basiljames

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2 Comments

David Over a year ago

It did turn out that inside the try block, that it made a call to another method which had a try block with a catch statement that explicitly reduced the exception (similar to your example except that they didn't hard-code "NullPointerException", but rather just truncated the cause of the stacktrace).

Stephen C Over a year ago

@David - I would be seriously considering switching to a different product. Deliberately suppressing exception information like that is going against the best interests of their customers / users. Find an alternative supplier that doesn't do this kind of crappy thing.

Chris · Accepted Answer · 2012-09-11 14:46:11Z

1

May be you don't have an appender for console output. You consider adding one. If not, log it as LOGGER.error(ex); with log4j or SLF4J

answered Sep 11, 2012 at 14:46

Chris

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1 Comment

David Over a year ago

For a while, I thought it might be due to console logging. So I tried storing the exception in a string and emailing it to myself. The email only contained "java.lang.NullPointerException"

Stephen C · Accepted Answer · 2012-09-11 15:06:03Z

1

I can only think of 2 reasons why e.printStackTrace() might output just the string "java.lang.NullPointerException".

Something might have called setStackTrace(new StackTraceElement[0]) on the exception.
The exception object might be an instance of a tricky class that has overridden the printStackTrace() or some other method to return misleading information.

answered Sep 11, 2012 at 15:06

Stephen C

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Comments

Gray · Accepted Answer · 2019-10-15 22:21:32Z

1

What might be blocking the above code from printing the full stacktrace?

In my case, a superclass of the Exception I was catching had this code:

/* avoid the expensive and useless stack trace for API exceptions */
@Override
public Throwable fillInStackTrace() {
    return this;
}

This meant that the stack trace array was never filled in so all I got was:

org.apache.kafka.AuthException: Auth failed: Invalid username or password

with no stack information so no idea where it happens. Lovely.

I was able to override this behavior by grabbing the source for the Exception, copying it into my project, and removing the fillInStackTrace() method. It's a hack but I needed information from that Exception.

edited Oct 15, 2019 at 22:21

answered Oct 15, 2019 at 22:12

Gray

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Comments

Spider · Accepted Answer · 2019-02-24 22:14:24Z

-1

Make sure you used e.printStackTrace(), instead of e.getStackTrace();

answered Feb 24, 2019 at 22:14

Spider

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