We Keep Coding

Determine if a java execution from another java application was done successfully

I have an application that calls a java test class in a specified location of my PC. The path is hard-coded for now, and I checked that it worked by executing it from the command line (in case you want to see it: java -cp C:\Users\user\Documents\workspace\test\build\test.jar org.junit.runner.JUnitCore us.test.DynamicWebserviceInvocationTest), so I know that the command works fine.
The thing is, when I do Runtime.getRuntime().exec(command), if I try to log the resulting InputStream and ErrorStream of its resulting process, the program stucks. I tried with exitValue() and waitFor(), but the first throws an incompletition error and the second also gets stuck. The weird thing is that if I don't touch anything of this (the streams, or using the functions), the program has no problem ending.
So my question is: Why could this be? The next step is to build the command with given parameters, but if I can't see the resulting inputs I can't be completely sure if the tests are running or not.
The code, in case you want to see it:
Runtime runtime=Runtime.getRuntime();
logger.debug("Attempting to execute the test {} at path {}",classpath,applicationLocation);
String command="java -cp C:\\Users\\user\\Documents\\workspace\\test\\build\\test.jar org.junit.runner.JUnitCore us.test.DynamicWebserviceInvocationTest";
Process process=runtime.exec(command);
BufferedReader stdInput = new BufferedReader(new
InputStreamReader(process.getInputStream()));
BufferedReader stdError = new BufferedReader(new
InputStreamReader(process.getErrorStream()));
System.out.println("Here is the standard output of the command:\n");
String s = null;
while ((s = stdInput.readLine()) != null) {
System.out.println(s);
}
System.out.println("Here is the standard error of the command (if any):\n");
while ((s = stdError.readLine()) != null) {
System.out.println(s);
}

You absolutely must read both streams in separate threads. (Read the Javadoc of the Process class). If you wait for the end, or read first one stream before the other it can happen that the output buffer of the command fills up and it will block (on stdout or stderr, depending on what you read first). Normally you use waitFor() in the current thread and have background thread draining the outputs (this also allows detecting end of child process without polling).
If you want to use only one (additional) thread you can redirect stderr to stdout. If you want to avoid to read the streams at all, you can set the
ProcessBuilder features inheritIO(). This allows the stream to be written to the existing output and so you do not need a thread to read independently.
There are BTW various libararies which offer exec tools (for example Apache Commons Exec has some streams) which offer active stream draining, logging or pumping for Process.
In addition to that it might also be a good idea to first close stdin, in case the command waits for input: p.getOutputStream().close();

Make sure you close the 2 streams:
String command="java -cp C:\\Users\\user\\Documents\\workspace\\test\\build\\test.jar org.junit.runner.JUnitCore us.test.DynamicWebserviceInvocationTest";
Process process=runtime.exec(command);
BufferedReader stdInput = new BufferedReader(new
InputStreamReader(process.getInputStream()));
BufferedReader stdError = new BufferedReader(new
InputStreamReader(process.getErrorStream()));
// read the output from the command
System.out.println("Here is the standard output of the command:\n");
String s = null;
while ((s = stdInput.readLine()) != null) {
System.out.println(s);
}
stdInput.close();
// read any errors from the attempted command
System.out.println("Here is the standard error of the command (if any):\n");
while ((s = stdError.readLine()) != null) {
System.out.println(s);
}
stdError.close();

Start and get output of a .jar (E.g. Minecraft Bukkit .jar)

I'm trying to start some .jar inside an .jar using this code: (I'm trying with craftbukkit server right know)
Runtime rt = Runtime.getRuntime();
Process p = rt.exec("java -jar craft.jar");
BufferedReader out = new BufferedReader(new InputStreamReader(p.getInputStream()));
BufferedWriter in = new BufferedWriter(new OutputStreamWriter(p.getOutputStream()));
this.running = true;
while(this.running){
String line;
if((line = out.readLine()) != null){
System.out.println(line);
}
}
The problem is, it work for a moment, but after a while it stops outputting or just print '>' as show in the image below. How can I fix this? **Plus, Which is the correct way to send commands to the bukkit server?
Thanks!

When using a Process in Java, it is crucial to read stdout and stderr in two independend threads (your while loop). Otherwise the child process can lock up waiting for the filled buffer to be drained.
With Java 7 you can actually redirect stderr to stdout, and possibly redirect the resulting stream to the parents stdout. With older versions you need to attach the seperate threads.
Besides: you should not use the "single string" variant of exec, but specify the args as arrays. This is safer (less vulnerable to parsing problems).
(But I am not sure if this is your actual problem. Maybe you should dump the error stream and see if it helps)

I do it like that:
#Override
public void run(){
// ...
BufferedReader stdInput = new BufferedReader(new InputStreamReader(proc.getInputStream())); //of course proc is an instance of Process, and it's set up
while(true){
String line = stdInput.readLine();
if(line == null) break; //this is essential, when process terminates, line gets null
System.out.println(">"+line);
}
// ...
}
Give it a try.
(Technically it's similiar how you did, but it works for me so i share it)

Java read Oracle EXP command output

I need to run the Oracle EXP command through a Java program and print somewhere the command output.
The EXP command is correct, the dump file is created correctly when I execute my Java code, but I'm experiencing some issues to get the output.
This is an snippet very similar to the one I'm using to read the output:
String line;
String output = "";
try {
Process p = Runtime.getRuntime().exec(myCommand);
BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
while ((line = input.readLine()) != null) {
output += (line + '\n');
}
input.close();
}
catch (Exception ex) {
ex.printStackTrace();
}
System.out.println(output);
As I said, the command is correctly executed (verified through the generated dump file), but nothing appears on my console and my Java programs doesn't terminate either.
The same code works perfectly if I use another command, as "ls -l" instead of "exp ...".

Maybe exp is writing to standard error output rather than standard output.
Try to use p.getErrorStream() instead of getInputStream()

As a_horse_with_no_name said, it might be that the error stream buffer is full and thus is blocking the programm execution.
Either try to start a Thread to also read the error stream or use the ProcessBuilder class to redirect the error stream to stdout (which you already read).

Call "interactive" Perl script from Java

I want to call an "interactive" Perl script from a Java program. Just for the clarity, the other way around (from Perl to Java) is not good for me.
The script is interactive in the sense that it requires a small configuration dialog with the user. For example, calling the script in cmd.exe would lead to a dialog like:
Do you want to overwrite the old settings? [yes,no (default=no)]
and the user should choose between writing yes, no or nothing at all in the command line.
And depending on the user choice another message would appear: "Do you want to...." and the user will respond etc etc. I think you got the picture.
My question is how can I have the same dialog with the user when the script is called in a Java program? I mean, how can I capture the script's questions to the user, show them to user and then send the user's answer (got in the Java program) to the script?
A simple Runtime.getRuntime().exec() doesn't work in this case.
Hope I expressed clear enough the question.
Thank you for your help!

You must use getInputStream/getOutputStream methods to get access to stdin and stdout of perl stript. You can read and write to these streams to simulate user's behavior
OutputStream stdin = null;
InputStream stderr = null;
InputStream stdout = null;
Process process = Runtime.getRuntime ().exec ("...");
stdin = process.getOutputStream ();
stderr = process.getErrorStream ();
stdout = process.getInputStream ();
// "write" the parms into stdin
String line = "data\n";
stdin.write(line.getBytes());
stdin.flush();
stdin.close();
// clean up if any output in stdout
BufferedReader brCleanUp =
new BufferedReader (new InputStreamReader (stdout));
while ((line = brCleanUp.readLine ()) != null) {
//System.out.println ("[Stdout] " + line);
}
brCleanUp.close();
// clean up if any output in stderr
brCleanUp =
new BufferedReader (new InputStreamReader (stderr));
while ((line = brCleanUp.readLine ()) != null) {
//System.out.println ("[Stderr] " + line);
}
brCleanUp.close();

This is a job for Expect. In Java: ExpectJ, expect4j

If (1) your call is from Java to Perl, and (2) you are not parsing the Perl script itself, why not use a JOptionPane.showConfirmDialog() from the Java code? Shouldn't be a big deal if a Yes/No is all your are getting from the script. Whatever you are printing to display to the user can be included in that confirm dialog as a plain ASCII text, too.

Running other programs from Java

I need to run a couple of other programs from my own Java program, basically I need to run these command line statements.
svn log --xml -v > svn.log
and
java -jar example.jar arg1 arg2
and I need to use the text outputs written to the console from these programs in my own program. I've tried Runtime.getRuntime().exec() with the svn, but it doesn't seem to be doing anything because it doesn't make a svn.log file. Also both programs need to be called in different places, the svn line needs to be called from inside one folder and the java line needs to be called from another.
Any ideas on how to go about this? If this is not possible in Java, is there a way to do it in C#?
Thanks

Here:
ProcessBuilder processbuilder
try
{
processbuilder.directory(file);
processbuilder.redirectErrorStream(true);
process = processbuilder.start();
String readLine;
BufferedReader output = new BufferedReader(new InputStreamReader(process.getInputStream()));
// include this too:
// BufferedReader output = new BufferedReader(new InputStreamReader(process.getErrorStream()));
while((readLine = output.readLine()) != null)
{
m_Logger.info(readLine);
}
process.waitFor();
}
I've used something similar. You'll actually want to do something with the readLine. I just copied and pasted from code where I didn't care what it said.

The redirection > (like the pipe |) is a shell construct and only works when you execute stuff via /bin/sh (or equivalent). So the above isn't really going to work. You could execute
/bin/sh -c "svn log --xml -v > svn.log"
and read svn.log.
Alternatively, you can read the output from the process execution and dump that to a file (if you need to dump it to a file, or just consume it directly as you read it). If you choose this route and consume stdout/stderr separately, note that when you consume the output (stdout), you need to consume stderr as well, and concurrently, otherwise buffers will block (and your spawned process) waiting for your process to consume this. See this answer for more details.

instead of piping in your command, just let it print to standard output and error output. You can access those streams from your process object that is returned from exec.

For the svn stuff use java SVNKit API.

Seeing your two commands, why don't you do it directly from Java, without executing ? You could use SVNKit for the svn part, and include directly the jars in your classpath.

Try this
public static void main(String[] args) {
try {
// Execute a command with an argument that contains a space
System.out.println(args[0]);
String[]commands = new String[]{"svn", "info", args[0]};
Process process = Runtime.getRuntime().exec(commands);
BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
StringBuilder builder = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
builder.append(line);
builder.append(System.getProperty("line.separator"));
}
String result = builder.toString();
System.out.println(result);
}catch(Exception e){
System.out.print(e);
}
}