I want to create a utility in Java to automate our building process. The current process involve
Opening 2 consoles for servers. ( I want to open these consoles from java program )
Running mulitple bat files in consoles and based on one batch file output, running other commands.
I need head start, what libraries should i use. Can i open 2 consoles from Java (independently). Like even if my program closes those consoles keep running. (consoles are bea server, startWebLogic.cmd).
Alee, yes you can do that with Runtime.getRuntime().exec("file.bat"); and then you have 2 options, you can capture the output of the execution
for example:
public static void main(String[] args) {
System.out.println("hello");
try {
Process p = Runtime.getRuntime().exec("./prog.sh");
InputStream in = p.getInputStream();
System.out.println("OUTPUT");
StringBuilder sb = new StringBuilder();
int c;
while( (c = in.read() ) > 0 ) {
sb.append((char) c);
}
//here the script finished
String output = sb.toString();
if( output.contains("Exception")) {
System.out.println("script failed");
}
if( p.exitValue() == 0) {
System.out.println("The script run without errors");
} else {
System.out.println("The script failed");
}
} catch (IOException e) {
e.printStackTrace();
}
}
this captures both scenarios, where you need to capture the output and then decide whether the script run successfully, or if you can use the exit status from the script.
The exitValue code is 0 for success and any other number for failure.
Surely you can open as many consoles as you want. If you wish to do it simultaneously creaete separate threads and then create process using Runtime.exec() or ProcessBuilder.
But why do you want to do this? There is a good old ant that is a build tool dedicated for such tasks. It supports everything and it is extendable using custom tasks.
Moreover if you suddenly remember that it is 2011 now, use newer tools like Apache Buildr.
Java's Runtime class has methods to launch Processes which have programmatic interfaces to their input/output streams and other management. However, I'm not sure how Windows handles processes whose parents have died.
You should also consider using the Windows Script Host via VB or JScript as you will probably have finer control.
Related
I am working on a simple meteo station - I want to use raspberry pi 3b+ as a host, dht22 sensor and write a web application in Java (with spring boot, then deploy it to tomcat 8) and Python for retrieving sensor's data.
What I've done so far:
Python application for retrieving and displaying data. Works as expected, it just prints something like "22.5;37.4":
import Adafruit_DHT
DHT_SENSOR = Adafruit_DHT.DHT22
DHT_PIN = 4
humidity, temperature = Adafruit_DHT.read_retry(DHT_SENSOR, DHT_PIN)
if humidity is not None and temperature is not None:
print("{0:0.1f};{1:0.1f}".format(temperature, humidity))
else:
print("FAIL")
Then I've wrote a java application, put it into .jar and checked if I am able to get sensor's data. Not a rocket science, also works as expected when I use java -jar InputTest.jar on my raspberry pi:
public static void main(String[] args) {
try {
ProcessBuilder pb = new ProcessBuilder("python", "/home/pi/Desktop/input/dht_once.py");
Process process = pb.start();
BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
String line;
while ((line = reader.readLine()) != null) {
System.out.println("measured: " + line);
}
process.waitFor();
} catch (IOException ) {
System.out.println(" exception " + e.getLocalizedMessage());
}
}
Then I've created a spring boot application, put my java code inside (logic same as above), packed as a war, deployed to tomcat 8 and run it. It turned out nothing is being printed (of course I've changed code to log output to logfile, it works fine, I can see other logs inside). No issues in logs, it looks like reader never returns a line.
I believe application does not wait for a process to produce output, but I have no idea why. Important thing: it takes up to few seconds to produce sensor's output. I've also changed python script just for test purposes to return value immediately:
print("22.4;33.0")
and it results in successful read by java web application. But when it has to wait few seconds for the output it kills process (process.isAlive() is false right after while loop).
I've also tried to play with sleep() on current thread to force it to wait for python process but no success.
Do you guys have any idea what can be the reason for this behavior? Is there anything more I should check?
TLDR;
Java application which creates python process works fine until I run it as a web application - then it looks like it does not wait for a process' output
I haven't found a solution yet, however I've implemented workaround/cleaner solution.
I've decided to separate totally java and python code and created microservice for data retrieving. I use flask for rest webservice (followed this tutorial https://docs.dataplicity.com/docs/control-gpios-using-rest-api) and call it directly from java.
Since this does not resolve my initial question I do not mark it as an answer, however it might help someone.
I'm running a jar file from another jar like here somebody answers but waiting for the process.
Process proc = Runtime.getRuntime().exec("java -jar A.jar" + stringParams);
try {
proc.waitFor();
} catch (InterruptedException e) {
e.printStackTrace();
}
InputStream in = proc.getInputStream();
InputStream err = proc.getErrorStream();
My problem comes when i have no feedback on the status of the program that is called, but i don't want my program continues beyond those lines. I would need the standard and error outputs but the results are shown when the execution is over. Is there any way of executing and getting those streams while the jar is still running?
Buffered/unbuffered
It seems like an issue with buffered output.
Executed process (in this case java -jar <path>) buffers output and writes it only when it's done (in big chunks, we don't like that!)
So one way to go is execute process through unbuffering (very hacky tools):
unbuffered <command>
stdbuf -i0 -o0 -e0 <command>
use terminal emulation
Hacking
stdbuf is part of GNU tools.
https://www.gnu.org/software/coreutils/manual/html_node/stdbuf-invocation.html
unbuffered is part of expect package.
https://wiki.tcl.tk/3548
The key thing is making the program thinking that it's in interactive mode (like you are launching it from console).
The first two options are very hacky and do not work in all cases (idk if java command works with them?)
Emulation
The third option is most promising.
We launch a program (terminal emulator) that emulates interactive terminal making program think it's working in real active session!
Pty4j
You might use pty4j too:
From there: https://github.com/traff/pty4j
// The command to run in a PTY...
String[] cmd = { "java", "-jar", "path_to_jar" };
// The initial environment to pass to the PTY child process...
String[] env = { "TERM=xterm" };
PtyProcess pty = PtyProcess.exec(cmd, env);
OutputStream os = pty.getOutputStream();
InputStream is = pty.getInputStream();
// ... work with the streams ...
// wait until the PTY child process terminates...
int result = pty.waitFor();
// free up resources.
pty.close();
Zt-exec
Maybe it's worth trying zt-exec?
I have no idea how it executes commands.
But it may be it (I didn't test that).
Using https://github.com/zeroturnaround/zt-exec
new ProcessExecutor().command("java", "-jar path_to_jar")
.redirectOutput(new LogOutputStream() {
#Override
protected void processLine(String line) {
...
}
})
.execute();
That should work, but I didn't test that.
In general, there are no ways to nicely resolve your problem.
Depending on what platforms you want to target consider using unbuffered, stdbuff or the (slowest) terminal emulation...
Please let me know if that helps and good luck! :)
How can I set the focus (e.g. cmd+tab) of an arbitrary application (Java or not) from a Java program, on OSX?
Looking for an answer to this question, I came across this question, but it doesn't really help for OSX.
EDIT: one possibiltiy seems to be to use something like Quicksilver, and a Robot to send it keypresses with modifiers. I'd prefer something more portable, though, that requires less setup to make changes after it's compiled....
You should be able to reactivate an already running app using the open command that comes with OS X:
Runtime.exec("open /path/to/Whichever.app");
(Or some equivalent overload of that function.) This will also open an app if it's not running yet.
Chuck's answer tipped me off to osascript, so I decided to give it a shot straight from the command line. Managed to get it working with Runtime.exec(), osascript, and AppleScript.
Java launches an AppleScript and passes it the application name, using osascript from the command line, via Runtime.exec():
try {
List<String> shellCommandList = new ArrayList<String>();
shellCommandList.add("osascript");
shellCommandList.add("activateApplication.scpt");
shellCommandList.add(appName);
String[] shellCommand = (String[])shellCommandList.toArray(new String[0]);
Process p = Runtime.getRuntime().exec(shellCommand);
// if desired, pipe out the script's output
BufferedReader in = new BufferedReader(new InputStreamReader(p.getInputStream()));
String cmdOutStr = "";
while ((cmdOutStr = in.readLine()) != null) {
System.out.println(cmdOutStr);
}
// if desired, check the script's exit value
int exitValue = p.waitFor();
if (exitValue != 0) {
// TODO: error dialog
System.err.println("Invalid application name: "+ appName);
}
} catch (Exception e) {
e.printStackTrace();
}
And the AppleScript uses a run handler to capture the incoming argument:
on run (arguments)
set appName to (item 1 of arguments)
tell application appName to activate
return 0
end run
You can use the javax.script API to run AppleScripts. So you can write a script along the lines of "tell application "WhateverApp" to activate", filling in your arbitrary application for WhateverApp, and it should do what you want.
In my program, I need to run a external command in a Ubuntu environment (ntpdate) using java. Currently my code looks like this:
Runtime rt = Runtime.getRuntime();
byte[] readBuffer = new byte[131072];
// Exec a process to do the query
Process p = null;
try {
p = rt.exec("ntpdate -q " + ip);
} catch (Exception ex) {
ex.printStackTrace();
}
if(p!= null){
try {
Thread.sleep(1000);
} catch (Exception e) {
}
// Read the input stream, copy it to the file
InputStream in = p.getInputStream();
try {
int count = 0, rc;
while ((rc = in.read(readBuffer, count, readBuffer.length - count)) != -1) {
count += rc;
if (count >= readBuffer.length) {
p.destroy();
break;
}
}
p.destroy();
result = processOutput(readBuffer, count);
} catch (IOException ex) {
ex.printStackTrace();
}
p.destroy();
This code need to be ran simultaneously on multiple threads in order to maximize performance (I need to test a list of 1.000.000 addresses using ntpdate). However, it runs very slowly, barely consuming machine processing. What am I doing wrong? How could I make this more efficient?
The same problem arises when trying to execute "dig" using .exec(), so I doubt it is because of the specific program being called. Is there some restriction in using Runtime.exec() in a multi Threaded environment?
Is Java the most appropriate approach here? Perhaps this would be better in a shell script, which calls ntpdate in the background multiple times? I'm not sure what benefit you're getting from this code snippet by doing this in Java.
What are you doing with the InputStream from the process?
A bash script could do this like:
for ip in #...IP list
do
ntpdate -q $ip > $ip.txt &
done
Why are you waiting for 1 second at each time ?
try {
Thread.sleep(1000);
} catch (Exception e) {
}
This will do nothing but slowing the execution of your application.
Not sure why it's slow but you need to do a lot more to close your resources. Runtime.exec() needs quite a bit of care and attention to avoid hang-ups and leaking of file descriptors.
http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html
Are you sure the issue isn't ntpdate? If ntpdate is just sitting there waiting for a server response and has a large timeout value, then your application is going to sit there too.
Try calling ntpdate with a timeout of 0.2 and see if it makes a difference.
Also, as you're opening streams in your code, you definitely want to explicitly .close() them when you're done. Otherwise it might not happen until a GC which could be a very long time away.
I think I found the solution, and that is that there is no solution using java's Runtime.exec(). The problem seems to be that all calls to start a process are synchronized. Indeed, if you start each process alone (via synchronization) you get the exact same result of starting all processes together.
Are there any alternatives to exec? Otherwise, I will need to get some solution without linux's ntpdate...
I notice that both of the commands you tried involve network round-trips. How is the speed if you call something like echo or cat instead?
I am working on a program written in Java which, for some actions, launches external programs using user-configured command lines. Currently it uses Runtime.exec() and does not retain the Process reference (the launched programs are either a text editor or archive utility, so no need for the system in/out/err streams).
There is a minor problem with this though, in that when the Java program exits, it doesn't really quit until all the launched programs are exited.
I would greatly prefer it if the launched programs were completely independent of the JVM which launched them.
The target operating system is multiple, with Windows, Linux and Mac being the minimum, but any GUI system with a JVM is really what is desired (hence the user configurability of the actual command lines).
Does anyone know how to make the launched program execute completely independently of the JVM?
Edit in response to a comment
The launch code is as follows. The code may launch an editor positioned at a specific line and column, or it may launch an archive viewer. Quoted values in the configured command line are treated as ECMA-262 encoded, and are decoded and the quotes stripped to form the desired exec parameter.
The launch occurs on the EDT.
static Throwable launch(String cmd, File fil, int lin, int col) throws Throwable {
String frs[][]={
{ "$FILE$" ,fil.getAbsolutePath().replace('\\','/') },
{ "$LINE$" ,(lin>0 ? Integer.toString(lin) : "") },
{ "$COLUMN$",(col>0 ? Integer.toString(col) : "") },
};
String[] arr; // array of parsed tokens (exec(cmd) does not handle quoted values)
cmd=TextUtil.replace(cmd,frs,true,"$$","$");
arr=(String[])ArrayUtil.removeNulls(TextUtil.stringComponents(cmd,' ',-1,true,true,true));
for(int xa=0; xa<arr.length; xa++) {
if(TextUtil.isQuoted(arr[xa],true)) {
arr[xa]=TextDecode.ecma262(TextUtil.stripQuotes(arr[xa]));
}
}
log.println("Launching: "+cmd);
Runtime.getRuntime().exec(arr);
return null;
}
This appears to be happening only when the program is launched from my IDE. I am closing this question since the problem exists only in my development environment; it is not a problem in production. From the test program in one of the answers, and further testing I have conducted I am satisfied that it is not a problem that will be seen by any user of the program on any platform.
There is a parent child relation between your processes and you have to break that.
For Windows you can try:
Runtime.getRuntime().exec("cmd /c start editor.exe");
For Linux the process seem to run detached anyway, no nohup necessary.
I tried it with gvim, midori and acroread.
import java.io.IOException;
public class Exec {
public static void main(String[] args) {
try {
Runtime.getRuntime().exec("/usr/bin/acroread");
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("Finished");
}
}
I think it is not possible to to it with Runtime.exec in a platform independent way.
for POSIX-Compatible system:
Runtime.getRuntime().exec(new String[]{"/bin/sh", "-c", "your command"}).waitFor();
I have some observations that may help other people facing similar issue.
When you use Runtime.getRuntime().exec() and then you ignore the java.lang.Process handle you get back (like in the code from original poster), there is a chance that the launched process may hang.
I have faced this issue in Windows environment and traced the problem to the stdout and stderr streams. If the launched application is writing to these streams, and the buffer for these stream fills up then the launched application may appear to hang when it tries to write to the streams. The solutions are:
Capture the Process handle and empty out the streams continually - but if you want to terminate the java application right after launching the process then this is not a feasible solution
Execute the process call as cmd /c <<process>> (this is only for Windows environment).
Suffix the process command and redirect the stdout and stderr streams to nul using 'command > nul 2>&1'
It may help if you post a test section of minimal code needed to reproduce the problem. I tested the following code on Windows and a Linux system.
public class Main {
/**
* #param args the command line arguments
*/
public static void main(String[] args) throws Exception {
Runtime.getRuntime().exec(args[0]);
}
}
And tested with the following on Linux:
java -jar JustForTesting.jar /home/monceaux/Desktop/__TMP/test.sh
where test.sh looks like:
#!/bin/bash
ping -i 20 localhost
as well as this on Linux:
java -jar JustForTesting.jar gedit
And tested this on Windows:
java -jar JustForTesting.jar notepad.exe
All of these launched their intended programs, but the Java application had no problems exiting. I have the following versions of Sun's JVM as reported by java -version :
Windows: 1.6.0_13-b03
Linux: 1.6.0_10-b33
I have not had a chance to test on my Mac yet. Perhaps there is some interaction occuring with other code in your project that may not be clear. You may want to try this test app and see what the results are.
You want to launch the program in the background, and separate it from the parent. I'd consider nohup(1).
I suspect this would require a actual process fork. Basically, the C equivalent of what you want is:
pid_t id = fork();
if(id == 0)
system(command_line);
The problem is you can't do a fork() in pure Java. What I would do is:
Thread t = new Thread(new Runnable()
{
public void run()
{
try
{
Runtime.getRuntime().exec(command);
}
catch(IOException e)
{
// Handle error.
e.printStackTrace();
}
}
});
t.start();
That way the JVM still won't exit, but no GUI and only a limited memory footprint will remain.
I tried everything mentioned here but without success. Main parent Java process can't quit until the quit of subthread even with cmd /c start and redirecting streams tu nul.
Only one reliable solution for me is this:
try {
Runtime.getRuntime().exec("psexec -i cmd /c start cmd.cmd");
}
catch (Exception e) {
// handle it
}
I know that this is not clear, but this small utility from SysInternals is very helpful and proven. Here is the link.
One way I can think of is to use Runtime.addShutdownHook to register a thread that kills off all the processes (you'd need to retain the process objects somewhere of course).
The shutdown hook is only called when the JVM exits so it should work fine.
A little bit of a hack but effective.