Develop Reference

Not able to execute a jar file using php exec, though it works in the terminal

I have a jar file I need to call from PHP, Jar is running good when I directly hit it from terminal like this
java -cp vajavastlib.jar:. GetVirtualCard
I am using ubuntu 15.04. But when I call it in a controller (using yii framework) like this
exec("java -cp vajavastlib.jar:. GetVirtualCard");
its returning empty string.
Thanks for the help in advance.

Probably you are not able to see the output or any error. The output is not going to the php handler. Add 2>&1 in your command at the end.
It will definitely show the output.
Also, make sure the jar file is in a public directory.

Trying to rename a computer OR execute a .bat file in Java

I'm trying to write a script to rename a computer (among other things) but just can't seem to figure it out. I don't really care what method I use to change the computer as long as i can change it. I found out how to read the computer name by doing
String computername = InetAddress.getLocalHost().getHostName();
However, that doesn't seem to offer any help in setting the computer name. Is there a way to set the Computer Name directly in the java console?
If not, or if anyone has better experience in this area, I also wrote a script using powershell 2.0 that renames the computer. I'm trying to figure out how to run that using
Runtime rt = Runtime.getRuntime();
Process proc = rt.exec("file location");
I followed the guide here but when trying to run a test .bat file that should just open the command line I just get this output in the java console:
C:\Users\Stephen\Desktop\opencmd.bat is found
OUTPUT>
OUTPUT>C:\Users\Stephen\workspace\UNM computer rename>cmd.exe
OUTPUT>Microsoft Windows [Version 6.1.7601]
OUTPUT>Copyright (c) 2009 Microsoft Corporation. All rights reserved.
OUTPUT>
It looks like it's just spitting back the command line output into the java console, instead of just running the command and opening the cmd line.
I would really appreciate input as I'm in a crunch for time here, thanks!

First, JDK really does not provide pure java API that allows changing computer name. So you have to run script.
Second, if you want to run script using Runtime you have to provide correct command line. So first try to run your script manually. I believe it accepts a least one parameter (the new computer name). So run it from command prompt and see it is working. Then put it to the working directory of your java program and copy/paste the command line into the java code and see that it is working now. if you want you can read STDOUT of your script and/or get its return code. If you do not care about its output just call process.waitFor() and then get the return code.
Be careful with arguments. Windows computer name may contain unicode characters and spaces. If it contains spaces surround it with quotes. Concerning unicode just try. I hope it will not cause problems to you.
You can also use ProcessBuilder class that allows better and more portable arguments passing.
Good luck.

It looks like opencmd.bat is being executed, so assuming your PowerShell script works, is it possible you don't have administrative privileges?
You can also do it elegantly using JNA, I think this would be the target. But if you are rushed for time, don't bother.

Matlab and Java integration

I have done image processing in MATLAB and build my GUI in Java. I want to integrate MATLAB into Java. I want to use MATLAB Builder for this purpose. I want also to use neural network for classification. There are some excel files also. Is it possible that this code will be integrated in Java?
My other question is that I want used MATLAB BuilderJA to know how it works. When I type java -version command, it gave me this error.
??? Attempt to execute SCRIPT java as a function:
C:\Program Files\MATLAB\R2009b\toolbox\matlab\general\java.m
C:\Program Files\Java\jdk1.6.0_21
When I use build command it gave me this error.
'javac' is not recognized as an internal or external command,
operable program or batch file.
Error: An error occurred while shelling out to javac (error code = 1).
Unable to build executable.
I have JDK installed. The path is C:\Program Files\Java\jdk1.6.0_21. I am using R2009b version
I want to run my code in Java, but I do not know how to fix this error. Can any one tell me how to resolve this error?

The first error message which you get when you type java -version is a bit misleading; instead of
java -version
you need to say
!java -version
since you want to call an external program and not a MATLAB script or function. As stated in the comments by Amro this will only work if the directory containing java.exe is on your path. See Running External Programs in the MATLAB help for more info.
The error message you get comes from the fact that
there happens to be a file java.m and MATLAB thinks you are trying to call this file
that file only contains comments, since java is actually a sort of keyword in MATLAB, see doc java.
MATLAB realizes that you are not using the keyword in its correct form (which would be to call java.something to create an object of class something) since you give a parameter
MATLAB ends up telling you in a strange way that java doesn't accept parameters (even though java.m does not contain the script, only its documentation)
Note that if you don't want to add the directory containing java.exe and javac.exe to the path, you could also try calling them with their full path name:
!C:\Program Files\Java\jdk1.6.0_21\blablabla\bin\javac.exe

Execute .jar from Python

I am trying to build a very simple python script to automate minifying/combining some css/js assets.
I am not sure how to properly handle the minification step. I use yui-compressor and usually call the jar directly from the command line.
Assuming the build script is in the same directory as rhino js.jar and yui-compressor.jar, I'd be able to compress a css/js file like so:
java -cp js.jar -jar yuicompressor-2.4.4.jar -o css/foo.min.css css/foo.css
Calling that from the terminal works fine, but in the python build file, it does not
eg, os.system("...")
The exit status being returned is 0, and no output is being returned from the command (for example, when using os.popen() instead of os.system())
I'm guessing it has something to do with paths, perhaps with java not resolving properly when calling to os.system()… any ideas?
Thanks for any help

I have a somewhat similar case, when I want a python program to build up some commands and then run them, with the output going to the user who fired off the script. The code I use is:
import subprocess
def run(cmd):
call = ["/bin/bash", "-c", cmd]
ret = subprocess.call(call, stdout=None, stderr=None)
if ret > 0:
print "Warning - result was %d" % ret
run("javac foo.java")
run("javac bar.java")
In my case, I want all commands to run error or not, which is why I don't have an exception raised on error. Also, I want any messages printed straight to the terminal, so I have stdout and stderr be None which causes them to not go to my python program. If your needs are slightly different for errors and messages, take a look at the http://docs.python.org/library/subprocess.html documentation for how to tweak what happens.
(I ask bash to run my command for me, so that I get my usual path, quoting etc)

os.system should return 0 when the command executes correctly. 0 is the standard return code for success.
Does it print output when run from the command line?

Why would you want to do this in Python? For tasks like this, especially Java, you are better off using Apache Ant. Write commands in xml and then ant runs for you.

Runtime exec output path

I am trying to run a perl command with Java runtime exec in linux/ubuntu/gnome. The command generates an pdf file, but it saves it in my home folder. Is there any way that the exec method can set an output path for the commands executed? Thanks in advance.

The exec method just runs the command on the operating system, so you'll want to change the command you're running with exec more than anything in "Java" per se.
There are a few possibilities:
Change the working directory of your java program. The .pdf is being saved in your working directory because this is where the program is being run.
Unfortunately it's not simple to change this value after the program has been launched. It is, however, trivial to change before the program starts; just change the working directory before starting the program.
Move the file to it's desired location after it's been created in your home directory.
Change the command so that it includes the target location. Your perl script may have an option that will enable you to save it's output to a certain location (usually -o or --output). Using this your program would change from:
Runtime.exec("perl someprogram");
to something like:
Runtime.exec("perl someprogram -o /path/to/some.file")
You might be able to use "output redirection", if there is no option to do this.
Try something like what's below as your argument:
Runtime.exec("perl someprogram > /path/to/some.file")
Unfortunately, without knowing more details of your situation I can't provide more concrete advice.
While each approach has benefits and drawbacks, it's probably best to just implement the one that you understand best; if you can't get one to work, try another.
A good, free online resource for learning is Introduction to Linux: A Hands On Guide.
Section 2.2 has details on cd which you can use for 1..
Section 3.3, section 3 teaches about the mv command, which will be useful in 2..
Section 5.1 is about I/O redirection. Knowing about "output redirection" and the > operator, are important for 4..
For 3., you'll have to consult the documentation of the perl program you're using.

You could modify the Perl script to accept an absolute path for the output.
You can trying setting the working directory using exec(java.lang.String[], java.lang.String[], java.io.File) where File is the directory the command is executed from.
If all else fails, you'll can always copy the generated file from the Home directory to your final location.