I have a class that manages the creation of RTF documents and a method in that class that calls the RTF editor with a XML file for display.
All but one user can access this editor without any issues. This one user consistently runs into an issue where their application just hangs. There are no errors in any logs. Normally this kind of problem is easily identified, reproduced and corrected, however, I can't for the life of my reproduce it so my attempts at debugging are failing.
Basically the code is as follows:
int exitVal = CUBSRTFEditor.runRTFEditor("c:\\tmp\\control"+ap_doc_id+".xml", xml,"I:\\AppealsLetters.exe /process \"c:\\tmp\\control"+ap_doc_id+".xml\"");
public static int runRTFEditor(String xmlLocation, String xmlContent, String executePath)
{
int exitVal = 0;
createLocalFile(xmlLocation, xmlContent);
try
{
System.out.println("executePath must = "+executePath);
Runtime rt = Runtime.getRuntime();
Process proc = rt.exec(executePath);
System.out.println("after executePath runs");
//exhaust that stream before waiting for the process to exit
InputStream inputstream = proc.getInputStream();
InputStreamReader inputstreamreader = new InputStreamReader(inputstream);
BufferedReader bufferedreader = new BufferedReader(inputstreamreader);
// read the ls output
String line;
while ((line = bufferedreader.readLine())!= null)
{
System.out.println(line);
}
exitVal = proc.waitFor();
}
catch (Throwable t)
{
t.printStackTrace();
}
CUBSRTFEditor.deleteTempFile(xmlLocation);
return exitVal;
}
The last output is the first System.out. When I take the xml file and execute this on any other PC it executes without issue. I see no useful info in proc.getErrorStream() or proc.getOutputStream().
The JDK's Javadoc documentation on this problem (exec hanging):
Because some native platforms only provide limited buffer size for standard input and output streams, failure to promptly write the input stream or read the output stream of the subprocess may cause the subprocess to block, and even deadlock.
I try exhausting that stream before waiting for the process to exit and that does not seem to help as it never seems to get to that point (the second System.out is not displayed)
Have I implemented this incorrectly? Am I missing something important? Any ideas on how to get more info out of the process would be great.
I am stuck....
Runtime.exec() is a deceptively nasty little spud to work with. I found this article (old, but still relevant) to be quite helpful. You can always skip to Page 4 for some highly gankable sample code. :-)
At a glance, your code needs to handle both proc.getOutputStream() and proc.getErrorStream(), which is a good reason to handle those streams in separate threads.
I wanted to update this because the change went into Production today and worked. Based off of BlairHippo's suggestions I got it to work with an anonymous inner class to create a separate thread to exhaust both the Error and Input streams.
new Thread(new Runnable(){
public void run()
{
try
{
BufferedReader br = new BufferedReader(new InputStreamReader(proc.getErrorStream()));
String line;
while ((line = br.readLine())!= null)
{
System.out.println(line);
}
}
catch (Throwable t)
{
t.printStackTrace();
}
}
}).start();
Related
I have written a java code in Eclipse and i am developing a plug-in which embed a button on workbench. When this button is clicked, it opens a batch file (located in c:/program file/prism 4.0/bin)
The code successfully opens the .bat file ! But my next task is write the output of that batch file on my console. I am using Eclipse IDE version 3.
My code is
MessageConsoleStream out = myConsole.newMessageStream();
out.println("We are on console ! \n Shubham performed action");
try {
ProcessBuilder pb=new ProcessBuilder("C:\\Program Files\\prism-4.0\\bin\\prism.bat");
pb.directory(new File("C:\\Program Files\\prism-4.0\\bin"));
Process p=pb.start();
int exitVal=p.waitFor();
out.println("Exited with error code "+exitVal+" shown and action performed \n");
out.println("Shubham Process Successful");
out.println("Printing on console");
}
catch (Exception e)
{
out.println(e.toString());
e.printStackTrace();
}
}
Do like this:
.....
Process p = pb.start();
BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
String in;
while((in = input.readLine()) != null) {
out.println(in);
}
int exitVal = p.waitFor();
.....
Note that if the batch file writes to standard error your java program must consume it otherwise the p.waitFor() will never return.
Do yourself a big favor and check http://commons.apache.org/exec/. It will take care of all the awful details about managnig an external process: timeout, handling input/output, even creating the command line will be easier and less error prone
Note that to correctly read from the InputStreams of a Process, you should do so on separate Threads. See this similar question.
I have a program that takes in a file as an input and produces an xml file as an output. When I call this from the command line it works perfectly. I try calling it from a Java program with the following code.
try
{
Process proc = Runtime.getRuntime().exec(c);
try
{
proc.waitFor();
}
catch(InterruptedException e)
{
System.out.println("Command failed");
}
}
catch(IOException e)
{
System.out.println("Command failed");
e.printStackTrace();
}
The program seems to be running fine, as it creates an xml file; however, the xml file is empty when I open it. I'm not encountering any exceptions in my Java program, so I'm baffled as to what the problem could be. Why would the command line program work fine normally, but then when called from Java not output anything to the file it created. I was thinking maybe it was some sort of permissions thing. I tried running the program as sudo (I'm using Linux) but to no avail. This problem doesn't seem to be anything I could find an answer to online. Hopefully somebody on here might be able to tell what's going on. :)
Get the output and error streams from your process and read them to see what is happening. That should tell you what's wrong with your command.
For example:
try {
final Process proc = Runtime.getRuntime().exec("dir");
try {
proc.waitFor();
} catch (final InterruptedException e) {
e.printStackTrace();
}
final BufferedReader outputReader = new BufferedReader(new InputStreamReader(proc
.getInputStream()));
final BufferedReader errorReader = new BufferedReader(new InputStreamReader(proc
.getErrorStream()));
String line;
while ((line = outputReader.readLine()) != null) {
System.out.println(line);
}
while ((line = errorReader.readLine()) != null) {
System.err.println(line);
}
} catch (final IOException e) {
e.printStackTrace();
}
If there is no output in either stream, then I would next examine the external program and the command being sent to execute it.
Did you try launching the process from outside java?
For me, I wrote a jar file that output a file and ran that from the command line in another java program. It turns out that there was a fundamental check in my jar file that I had forgotten about on the number of characters in an input string (my bad). If the count of the characters was smaller than 8 there was no output file. If the number of characters was greater than 8, the output file came out without any trouble using the following code:
String cmdStr = "java -jar somejar.jar /home/username/outputdir 000000001";
try
{
Runtime.getRuntime().exec(cmdStr);
Runtime.getRuntime().runFinalization();
Runtime.getRuntime().freeMemory();
log.info("Done");
}
catch (IOException e)
{
log.error(System.err);
}
Not sure if I really need everything here but, hey, it works. Note: no waitFor seems to be necessary in my case.
process input (actually output of the process!) and error streams has to be handled before waiting for the process termination.
This should work better
try
{
Process proc = Runtime.getRuntime().exec("anycomand");
BufferedReader outSt = new BufferedReader(new InputStreamReader(proc.getInputStream()));
BufferedReader errSt = new BufferedReader(new InputStreamReader(proc.getErrorStream()));
String line;
while ((line = outSt.readLine()) != null)
{
System.out.println(line);
}
while ((line = errSt.readLine()) != null)
{
System.err.println(line);
}
proc.waitFor();
}
catch (final IOException e)
{
e.printStackTrace();
}
but to understand better how Runtime exec works it is worth reading
the classic article
When Runtime.exec() won't
which provide useful sample code (better than the one above!)
Sorry for this odd-sounding title...
I have the following situation: I want my Java program to interact with an external console. In order to "send" the individual commands to that console, I need to simulate what would be an "enter key pressed" on a normal console. To clarify what I want, imagine mysql had no other API and I would need to interact via console. Although this is not my actual problem, it is close enough.
I have the following code:
String command = "/usr/local/mysql/bin/mysql";
Process child = Runtime.getRuntime().exec(command);
StreamGobbler gobbler = new StreamGobbler(child.getInputStream());
gobbler.start();
BufferedWriter out = new BufferedWriter(new OutputStreamWriter(child.getOutputStream()));
out.write("help");
// here enter key needs to be pressed
out.flush();
// out.close();
If the call to out.close() is executed, everything is fine. But of course, this way I can only send a single command, which is not what I want. But if out.close() is omitted, the other program never executes the command. My guess is that it still waits for the command to "finish", which on a normal console would be done by pressing enter. out.write(System.getProperty("line.separator")); and out.newLine(); (which are the same) do not solve the problem, neither does out.write("\r\n"); and out.write((char) 26); (EOF).
Of course, it might be, that I am doing it completely wrong (i.e., wrong approach). Then I would appreciate a pointer into the right direction...
Any help on this highly appreciated.
The following code works fine on both Windows 7 using Java 1.6.0_23 and on Ubuntu 8.04 using Java 1.6.0_22:
public class Laj {
private static class ReadingThread extends Thread {
private final InputStream inputStream;
private final String name;
public ReadingThread(InputStream inputStream, String name) {
this.inputStream = inputStream;
this.name = name;
}
public void run() {
try {
BufferedReader in = new BufferedReader(
new InputStreamReader(inputStream));
for (String s = in.readLine(); s != null; s = in.readLine()) {
System.console().writer().println(name + ": " + s);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
public static void main(String[] args) throws Exception {
String command = "psql -U archadm arch";
final Process child = Runtime.getRuntime().exec(command);
new ReadingThread(child.getInputStream(), "out").start();
new ReadingThread(child.getErrorStream(), "err").start();
BufferedWriter out = new BufferedWriter(
new OutputStreamWriter(child.getOutputStream()));
out.write("\\h");
out.newLine();
out.flush();
out.write("\\q");
out.newLine();
out.flush();
}
}
newLine() is the same as writing the platform line separator. As one would expect, it prints help preceded with "out: ", then exits. If I don't send "\q", it doesn't exit (obviously) but still prints help. Using "\r\n" or "\r" instead of the platform line separator doesn't look like a good idea to me, because such command-line utilities will usually detect that they don't get input from the terminal and assume it is in the native text format (think "psql < script.sql"). Good software should properly detect and accept all reasonable line endings though.
What about out.write((char) 13)? See this Wikipedia article. I don't have enough code to test this for you.
You also might want to try looking at this API
http://download.oracle.com/javase/6/docs/api/java/io/Console.html
From my experience, I've never tried doing anything more than running one process from the Process API. It seems like you want to enter multiple commands I think this API might let you do that.
EDIT: Found a tutorial on it to help you further.
http://download.oracle.com/javase/tutorial/essential/io/cl.html
Hope this helps,
Im trying to get console output from an external application in my application. When i call the externall app from my code it hangs with the message:
Configuring logging...
Configuring log4j from: C:\GPAT\log4j.cfg
and nothing happens. I searched through internet and it seems that it might be thread issue. But i cant modify this external application and i must go through log4j. I read the external app like this:
StringBuffer output = new StringBuffer();
try {
Runtime rt = Runtime.getRuntime();
Process proc = rt.exec(GSATCommand);
BufferedReader input = new BufferedReader(new InputStreamReader(proc.getInputStream()));
System.out.println("Test running...");
String line = null;
while ((line = input.readLine()) != null) {
System.out.println(line); // Writes the test output to console
output.append(line); output.append("\n");
}
int exitVal = proc.waitFor();
System.out.println("Process exitValue: " + exitVal);
System.out.println("Test successfully executed");
} catch (Throwable t) {
t.printStackTrace();
}
Thanks for reading.
You need to consume both stdout and stderr from a spawned process in separate threads, to prevent blocking behaviour (your spawned process will write to buffers, and block if those buffers aren't being emptied by your consuming process).
See the 2nd paragraph of this answer for more details and a link to a suitable fix.
I am using a thread to capture stream output from a process, and then outputting that stream to the eclipse console. The question I have is when to terminate the thread that is doing the stream output.
Thread t = new Thread(new Runnable(){
private boolean isProcessDone(Process p)
{
//not sure what to do here
}
public void run()
{
Process p = Runtime.getRuntime().exec("executable with output");
BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
BufferedReader error = new BufferedReader (new InputStreamReader(p.getErrorStream()));
while ( !isProcessDone(p) ) {
String line;
if( (line = input.readLine()) != null )
{
System.out.println(line);
}
if( (line = error.readLine()) != null )
{
System.out.println(line);
}
}
input.close();
error.close();
}
});
t.start();
My question is what belongs in the isProcessDone() function. The example I am basing this off of uses the stream's ready() function, but I am unclear whether this will work for programs that either std::err and std::out, but not both. I also tried using
try{
p.exitValue();
return true;
}catch(IllegalThreadStateException e){}
return false;
but then the thread finishes before the while loop has a chance to act on the streams, and the output is lost.
You need to use Process.waitFor() to wait for process completion.
Additionally, you need to consume stdout and stderr concurrently in order to avoid blocking and a possible process hang. Consequently you need two threads to read these streams, and to continue reading whilst the streams are available.
See this Javaworld article for more info and a StreamGobbler implementation to consume the stdout/err.
You can use VerboseProcess from jcabi-log (I'm a developer):
String name = new VerboseProcess(
new ProcessBuilder("executable with output")
).stdout();
The only dependency you need:
<dependency>
<groupId>com.jcabi</groupId>
<artifactId>jcabi-log</artifactId>
<version>0.7.5</version>
</dependency>
You will need to have two threads. One to handle the I/O and another to wait for process completion (Process.waitFor()) and set a flag telling the I/O thread to quit when it exhausts the data.
You need to process reading the output in a separate thread, theres an example here