I'm into a quite strange position (from my java-newbie point of view):
using Eclipse I wrote a "java program" (some .java files with classes into) which essentially (batch) reads a text *.csv file, "evaluates" its contents, and writes out results into an *_out.csv text file. To locate the input file it uses a "file chooser" (got sample from here: http://docs.oracle.com/javase/tutorial/uiswing/components/filechooser.html)
I debugged all the code and, using the debugger, it works.
I ran the code (the main class, which calls all the other in sequence) and it works, while in Eclipse.
I exported all the project's contents into a "runnable jar" file.
Notice that, file chooser apart, this is mainly a "batch" which reads and writes: nearly no User Interface at all. While into Eclipse I shown some internal results using something like "if(debug) System.out.print("something to print");" providing to set "debug" TRUE while debugging and FALSE while in production environment.
ALL of the above worked!
Now, starting the runnable jar (double-click on the jar file, in Win/XP), I can see the file chooser and I can use it but, after choosing the input file... nothing more: (having no user interface) I don't know if the file was read, I don't see any generated output file, and I've even no "console" to list any intermediate debug message, to see if the jar is working, even if I re-export it with the debug variable set to TRUE.
Is there a way to "runtime debug" the running jar (like VB's MsgBox, or something other)? some kind of "log file" I can "enable" or look into? (obviously, as my jar is not writing the result file, I just can't try writing a *.log too) I have also to say I just can't install other than Eclipse on my machine (and just been lucky it ran), so no usual developer's tools, utilities and other useful things.
You can activate JVM's debugging capability when starting up the java
command with a special option:
java -agentlib:jdwp=transport=dt_socket,address=8000,server=y,suspend=y -jar path/to/some/war/or/jar.jar
Starting up jar.jar
like that on the command line will:
server=y
) listening on port 8000 (address=8000
)Listening for transport dt_socket at address: 8000
to stdout
andsuspend=y
) until some debugger connects. The debugger acts as the client in this scenario.Common options for selecting a debugger are:
jar.jar
should begin executing.jdb -connect com.sun.jdi.SocketAttach:port=8000
http://www.eclipsezone.com/eclipse/forums/t53459.html
Basically run it with:
-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=1044
The application, at launch, will wait until you connect from another source.
With IntelliJ IDEA
you can create a Jar Application
runtime configuration, select the JAR
, the sources, the JRE
to run the Jar
with and start debugging. Here is the documentation.
Source: Stackoverflow.com