Is it possible that the exception is being thrown in a different thread? If that’s the case, you can use:
https://docs.oracle.com/javase/7/docs/api/java/lang/Thread.UncaughtExceptionHandler.html <https://docs.oracle.com/javase/7/docs/api/java/lang/Thread.UncaughtExceptionHandler.html> to capture it. Rob. > On 2 Nov 2015, at 12:22, Lawrence Krubner <lawre...@rollioforce.com> wrote: > > > Now there is a new error. > > Somehow, when the exception happens in our Java library, even though we, in > theory, write to System.out.println(), I never see the Exception in the logs. > > All I can think is that somewhere in the Java library there is an exception > that we catch but we forget to do System.out.println(). Can anyone think of > another explanation? > > > > > On Sunday, November 1, 2015 at 5:10:19 PM UTC-5, Lawrence Krubner wrote: > So, we eventually fixed this. There were 2 bugs that worked together to make > this a mystery. I had to guess at what the problems were, and fix them blind, > since I could not see the Exceptions. I am curious about why I was not able > to see the Exceptions. > > About this: > > > Exceptions are ALWAYS visible, the only way they get lost is > > the try/catch blocks you added in your code which effectively > > swallow and ignore them. > > But the Exceptions I dealt with were invisible. We have the Clojure app set > up to run via Supervisord and the conf has these lines: > > stderr_logfile=/var/log/nlph_stderr.log > stdout_logfile=/var/log/nlph_stdout.log > > So in 2 terminal windows I would: > > cd /var/log > > tail -f nlph_stdout.log > > And the same for nlph_stderr.log. > > So I was looking at the output in my terminal window. And I could see all of > our logging statements appear. And the code clearly got to the line where the > exception happens, but then the Exception never appeared in the terminal. It > was invisible. I assume the output of this: > > System.out.println(e.getMessage()); > > would appear in one of the files that I was tailing. But it never did. > > So I am wondering why the Exceptions were invisible? Why didn't the print > statements make it to the terminal? > > > > > On Saturday, October 31, 2015 at 6:56:23 AM UTC-4, Thomas Heller wrote: > > What could we do to make the Exception visible, assuming there is one? > > > Exceptions are ALWAYS visible, the only way they get lost is the try/catch > blocks you added in your code which effectively swallow and ignore them. The > JVM will not randomly lose an Exception, it is always code you write that > decided to handle them in some way. If you do not know how to handle an > exception do not catch it, printing its stacktrace and ignoring it is never a > good idea. > > In your case since you say that the function never returns I'd put my guess > on an infinite loop. There is no exception that gets lost, your code is just > still running. If your JVM is running locally you can attach to it via > jvisualvm [1] and get a quick overview of what the JVM is doing. If you look > at the thread information you'll see if something is still running or > dead-locked somehow. > > You can also use a debugger and step through the java code step by step. > > Also, consider coding against interfaces in java (eg. java.util.List and > java.util.Map instead of java.util.Collection), it will save you tons of > conversion calls. > > HTH > /thomas > > [1] https://visualvm.java.net/ <https://visualvm.java.net/> > > -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to clojure@googlegroups.com > Note that posts from new members are moderated - please be patient with your > first post. > To unsubscribe from this group, send email to > clojure+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/clojure?hl=en > <http://groups.google.com/group/clojure?hl=en> > --- > You received this message because you are subscribed to the Google Groups > "Clojure" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to clojure+unsubscr...@googlegroups.com > <mailto:clojure+unsubscr...@googlegroups.com>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
