I wanted to know the step-by-step internal process that happens on execution of a java program.
Example if we giv java test in command prompt.
What all process got invoked?
How JVM is instantiated ? till it prints the output..
The execution of java code internally will be in the following steps:-
Execution Command -->java Test
1.Start JVM
2.Create and Start Main Thread
3.Look at Test.class File-->Main Thread is responsible for checking if not found Runtime Exception will occur saying Exception in Thread Main
4.Load Test.class file
5.Execute Main method
6.Unload Test.class
7.Terminate Main Thread
8.Shut down JVM
I dont know but however, the concept that i have understood , I will explain you the same....
Initially, the very first when you enter the command java abc(filename is abc.java) to run the program....the program will search for Java Runtime Environment as you have entered command (JAVA in cmd)....it means the path that you have set in Environment Variable....
Then the JVM is activated........JVM will give a call to the class loader.......then the class loader will go to the operating system to take a permission for the program execution.....once OS allows.....class loader will check the file name and the program name........(As you know the class name and file name should be same)........If everything goes fine........program is loaded in the Memory.....:)
Cheers :)
Shankar Salunkhe
Related
I'm developing plugins for a program. Whenever I try to load my plugin in that program it crashes with an the specified procedure could not be foundbut nothing more.
Well to have an insight I tracked with Process Monitor (or ProcMon). I set the filter to just print messages for the process of my main program. However that application shows me including the libraries ends (after wandering through PATH) at the right file - i.e. Result: SUCCESS.
So my computer left me pretty clueless, yet refuses to work. Has anyone an idea how identify the missing procedure?
N.B.: Additionally I ran the DependencyWalker which gave me the usual error message because it's deprecated (dependency walker gives me errors on the system that runs correctly) - which could indicate that all dependencies are found.
I'm trying to create a piece of software that will not be susceptible to bots. Is there a way for me to code into a program a way to check in the operating system for a process just like it and then put in a shutdown mechanism if it is recognized. Think of something like netflix where if one tab in chrome is running netflix, a second tab being opened will display an "oops" message. Is there anything like this for something that does not run on a web browser? What should I be looking into?
Thanks in advance
There can be plenty of solutions; the first coming into my mind are:
1) your program checks for existence of a particular file; if the files is not found then the program continue, otherwise your programs know that another instance is running and thus can terminate immediately. If the file is not found, your program creates it and then delete it before exting.
2) you can use an operating system call or an o.s. utility program to know if another instance of your program is running (e.g.: in linux, the command ps)
have fun
Is it possible to start a specific command of a Spring-Shell app and then return/exit the shell after the command is finished? Further is it possible to expose the exit code (System.exit) of the app to the operating system shell?
For my purpose i will take advantage of the plugin mechanism and the CLI-Annotations of Spring-Shell. But in general there is no human interaction with the app, instead a job scheduler (UC4) will start the app and check the exit code to generate an email in case of an exit code not equal to 0. On the other hand for manual tests by our customer, there is also the need of tab completion, usage help etc.
This behavior is already built-in (although we considered removing it, or at least make it optional). I see now that it is useful :)
Simply invoke the shell with your (sole) command and the shell will spin up, execute the command, and quit. Also, the return code of the shell already indicates whether there was an error or not (tried with an inexistant command for example). Of course, if your custom commands do not properly indicate an error (i.e. print an error message but perform a normal return) this will not work. You should throw an exception instead.
The behavior is back.
Run spring-shell with #my-script, like so:
java -jar my-app.jar #my-script
Where my-script is a file with your commands:
my-command1 arg1 arg2
my-command2 arg1 arg2
Is there any way to call mprirun inside FORTRAN program? I'm working on public linux cluster via ssh and the main idea is to automatically enqueue program after its execution is over.
I tried to write something like this at the end of the program:
CALL system('mpirun -np 16 -maxtime 100 TestNP')
But recieved this error:
sh: mpirun: command not found
Any ideas ?
The problem is the missing path prefix, so specifying an absolute path for mpirun should help. However there are several problems with your approach:
If every MPI process executes it, you would have too many instances running, so only one of the nodes (e.g. the master node) should execute it.
The original program won't be finished, until the one called via the system() call did not finish. So, if your queue is wall-clock limited, you don't gain anything at all.
Typically, tasks like this are done via shell-scripts. E.g. in Bash you would write something like:
while true; do
mpirun your_program
done
This would re-invoke mpirun continuously until not killed by you or the queuing system. (So be careful with it!)
I'm trying to integrate running Fitnesse tests from MSBuild im my nightly build on TFS.
In an attempt to make it self contained I would like to start the seleniumRC server only when it's needed from fitness.
I've seen that there is a "Command Line Fixture" but it's written in java can I use that?
I think you might be able to. You can call any process easily in MSBuild using the task. However, the problem with doing this is that the exec task will wait for the Selinium process to finish before continuing, which is not the bahaviour you want. You want to run the process, keep it running during your build and then tear it down as your build finishes.
Therefore, I think you are probably going to need to create a custom MSBuild task to do this. See the following post for an example of a tasks that someone has created that will run asynchronously returning control back to the build script:
http://blog.eleutian.com/2007/03/01/AsyncExecMsBuildTask.aspx
And for an example of calling a Java program from MSBuild (but in this case synchronously) take a look at my task that calls Ant from MSBuild here
http://teamprise.com/products/build/
As part of your MSBuild task, you will want to output the process id that you created to an output property so that at the end of your build script you can call another custom MSBuild task that kills the process. It can do this by looking for the process id passed in as a variable in MSBuild and then call Process.Kill method i.e.
Process process = Process.GetProcessById(ProcessId);
process.Kill();
That said, you would need to be careful to ensure that your kill task was always executed in MSBuild by making sure it was included during error paths etc in the build. You could probably make things a bit more resilient by making the selenium RC starter task look for other seleniumRC processes and killing them before starting a new one - that way if a process didn't get closed properly for some reason, it would only run until the next build.
Anyway - my answer sounds like a lot of work so hopefully someone else will come up with an easier way. You might be able to create the seleniumRC process in the test suite start up of the FitNesse tests and kill it in the suite tear down, or you might be able to write a custom task that extends your FitNesse runner tasks and fires up seleiniumRC asynronously before running the test process and then kills it afterwards.
Good luck,
Martin.
Thanks for your replies!
This is how I've done so far.
I made a fit fixture (very simple) that starts a process with the supplied command line, in my case startSelenium.bat. The fixture returns the ProcessID so I can store that in my fitnesse context and close that session later.
I can now make a SuiteSetUp page in my fitnesse test that looks like this.
|RunCommandFixture|
|Commandline|RunCommand?|
|C:\Projects...\startSeleniumRC.bat|>>seleniumprocess|
and a SuiteTearDown like this
|RunCommandFixture|
|ProcessID|StopCommand?|
|<
That works for me. No selenium RC starts by request from my fitnesse test.
What about writing a simple .NET app that does a Process.Start("selenumRC commandline") which gets run by your build script?
If you aren't too far down the Selenium route; might I suggest that you look at similar .NET browser automation tools; specifically WatiN or ArtOfTest. The "stacks" in these are completely .NET, so getting them running on different machines is much easier.