I am executing a command which returns me the Revision number of a file; 'fileName'. But if there is some problem executing the command, then the application hangs up. What can I do to avoid that condition? Please find below my code.
String cmd= "cmd /C si viewhistory --fields=revision --project="+fileName;
Process p = Runtime.getRuntime().exec(cmd) ;
BufferedReader in = new BufferedReader(new InputStreamReader(p.getInputStream()));
String line = null;
while ((line = in.readLine()) != null) {
System.out.println(line);
}
} catch (Exception e) {
e.printStackTrace();
}
I guess the issue is that you are only reading InputStream and not reading ErrorStream. You also have to take care that both the streams are read in parallel. It may so happen that currently the data piped from the output stream fills up the OS buffer, your exec command will be automatically be suspended to give your reader a chance to empty the buffer. But the program will still be waiting for the output to process. Hence, the hang occurs.
You can create a separate class to handle both the Input and Error Stream as follows,
public class ReadStream implements Runnable {
String name;
InputStream is;
Thread thread;
public ReadStream(String name, InputStream is) {
this.name = name;
this.is = is;
}
public void start () {
thread = new Thread (this);
thread.start ();
}
public void run () {
try {
InputStreamReader isr = new InputStreamReader (is);
BufferedReader br = new BufferedReader (isr);
while (true) {
String s = br.readLine ();
if (s == null) break;
System.out.println ("[" + name + "] " + s);
}
is.close ();
} catch (Exception ex) {
System.out.println ("Problem reading stream " + name + "... :" + ex);
ex.printStackTrace ();
}
}
}
The way you use it is as follows,
String cmd= "cmd /C si viewhistory --fields=revision --project="+fileName;
Process p = Runtime.getRuntime().exec(cmd) ;
s1 = new ReadStream("stdin", p.getInputStream ());
s2 = new ReadStream("stderr", p.getErrorStream ());
s1.start ();
s2.start ();
p.waitFor();
} catch (Exception e) {
e.printStackTrace();
} finally {
if(p != null)
p.destroy();
}
This code is based on the same idea Arham's answer, but is implemented using a java 8 parallel stream, which makes it a little more concise.
public static String getOutputFromProgram(String program) throws IOException {
Process proc = Runtime.getRuntime().exec(program);
return Stream.of(proc.getErrorStream(), proc.getInputStream()).parallel().map((InputStream isForOutput) -> {
StringBuilder output = new StringBuilder();
try (BufferedReader br = new BufferedReader(new InputStreamReader(isForOutput))) {
String line;
while ((line = br.readLine()) != null) {
output.append(line);
output.append("\n");
}
} catch (IOException e) {
throw new RuntimeException(e);
}
return output;
}).collect(Collectors.joining());
}
You can call the method like this
getOutputFromProgram("cmd /C si viewhistory --fields=revision --project="+fileName);
Note that this method will hang if the program you are calling hangs, which will happen if it requires input.
Related
I call the.py file in a basic java project and it takes about 30 seconds to run.
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class Main {
public static void main(String[] args) {
Process proc;
String line ="";
BufferedReader in;
try {
proc = Runtime.getRuntime().exec("D:\\anaconda\\python.exe " +
"D:/2017/Python/pythonProject8/main.py " +
"D:\\2017\\Python\\pythonProject8\\flower1.jpg");
proc.waitFor();
in = new BufferedReader(new InputStreamReader(proc.getInputStream()));
while ((line = in.readLine()) != null) {
System.out.println(line);
}
in.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
result:
enter image description here
But this code is skipped when I use spring-boot.
#GetMapping("test")
public String test(){
System.out.println(1);
Process proc;
String line = "";
String result = "";
try {
proc = Runtime.getRuntime().exec("D:\\anaconda\\python.exe " +
"D:/2017/Python/pythonProject8/main.py " +
"D:\\2017\\Python\\pythonProject8\\flower3.jpg");// 执行py文件
proc.waitFor();
BufferedReader in = new BufferedReader(new InputStreamReader(proc.getInputStream()));
while ((line = in.readLine()) != null) {
System.out.println(line);
result += line;
}
in.close();
} catch (Exception e) {
e.printStackTrace();
}
System.out.println(2);
return result;
}
result:
enter image description here
I want to know how to run spring-boot properly.
thanks.
If your.py file takes a long time to run then you shouldn't use Process and use ProcessBuilder instead.
public ArrayList<String> getPasswords(String path) throws IOException {
String result = "";
ProcessBuilder processBuilder = new ProcessBuilder("D:\\anaconda\\python.exe ", "D:\\2017\\Python\\pythonProject8\\main.py",path);
//The path here is me.py needs to be passed in
processBuilder.redirectErrorStream(true);
final Process process = processBuilder.start();
final BufferedReader in = new BufferedReader(new InputStreamReader(process.getInputStream()));
String s = null;
int i = 0;
while ((s = in.readLine()) != null)//This if is I need to ignore some of the output
{
i++;
if (i >6) {
result += s + '\n';
}
}
if (!result.equals("")){
return new ArrayList<String>(Arrays.asList(result.split("\n")));
}
return new ArrayList<String>();
}
You may run an error "DLL load failed while importing XXXX".
Please update the packages required for python.
I am trying to run a script using Java and ProcessBuilder. When I try to run, I receive the following message: error=2, No such file or directory.
I dont know what I am doing wrong but here is my code (ps: I tried to execute just the script without arguments and the error is the same:
String[] command = {"/teste/teste_back/script.sh, "+argument1+", "+argument+""};
ProcessBuilder p = new ProcessBuilder(command);
try {
// create a process builder to send a command and a argument
Process p2 = p.start();
BufferedReader br = new BufferedReader(new InputStreamReader(p2.getInputStream()));
String line;
log.info("Output of running " + command + " is: ");
System.out.println("Output of running " + command + " is: ");
while ((line = br.readLine()) != null) {
log.info(line);
}
}
Try replacing
String[] command = {"/teste/teste_back/script.sh, "+argument1+", "+argument+""};
with
String[] command = {"/teste/teste_back/script.sh", argument1, argument};
Refer ProcessBuilder for more information.
ProcessBuilder(String... command)
Constructs a process builder with the specified operating system
program and arguments.
You can define a method with ProcessBuilder.
public static Map execCommand(String... str) {
Map<Integer, String> map = new HashMap<>();
ProcessBuilder pb = new ProcessBuilder(str);
pb.redirectErrorStream(true);
Process process = null;
try {
process = pb.start();
} catch (IOException e) {
e.printStackTrace();
}
BufferedReader reader = null;
if (process != null) {
reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
}
String line;
StringBuilder stringBuilder = new StringBuilder();
try {
if (reader != null) {
while ((line = reader.readLine()) != null) {
stringBuilder.append(line).append("\n");
}
}
} catch (IOException e) {
e.printStackTrace();
}
try {
if (process != null) {
process.waitFor();
}
} catch (InterruptedException e) {
e.printStackTrace();
}
if (process != null) {
map.put(0, String.valueOf(process.exitValue()));
}
try {
map.put(1, stringBuilder.toString());
} catch (StringIndexOutOfBoundsException e) {
if (stringBuilder.toString().length() == 0) {
return map;
}
}
return map;
}
You can call the function to execute shell command or script
String cmds = "ifconfig";
String[] callCmd = {"/bin/bash", "-c", cmds};
System.out.println("exit code:\n" + execCommand(callCmd).get(0).toString());
System.out.println();
System.out.println("command result:\n" + execCommand(callCmd).get(1).toString());
Unless your script.sh has a comma in its name, that is the mistake:
String[] command = {"/teste/teste_back/script.sh" , argument1, argument};
A simple example of using phantomJs in Java will block undefinitely:
public void runPhantomJs(String path, String command) {
Process process;
String outFile = "a11.txt";
try {
process = Runtime.getRuntime().exec(path+ " " + command + " > " +outFile);
int exitStatus = process.waitFor();
//String status = (exitStatus == 0 ? "SUCCESS:" : "ERROR:");
File f = new File(outFile);
if (f.exists()) {
BufferedReader in = new BufferedReader(new InputStreamReader(new FileInputStream(f),"UTF-8"));
String str;
while ((str = in.readLine()) != null) {
System.out.println(str);
}
in.close();
System.out.println(str);
}
} catch (IOException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
The script execute is very simple, but it returns a whole page on the console:
var webPage = require('webpage');
var page = webPage.create();
page.open('http://www.google.com/', function(status) {
if (status !== 'success') {
console.log('1');
phantom.exit();
} else {
console.log(page.content);
phantom.exit();
}
});
Note that on the pasted code I've added a "> a11.txt" to see if it worked better to read a file instead of reading the output directly. It should be faster, but for some reason it doesn't work. I suppose the redirection > doesn't work.
So I got my code to work. Apparently the output of phantomjs has to be read or the buffer will fill up completely, blocking further execution.
So I think your code will work if you modify it like so:
process = Runtime.getRuntime().exec(path+ " " + command + " > " +outFile);
BufferedInputStream bis = new BufferedInputStream(process.getInputStream());
bis.close();
process.waitFor();
...
If it doesn't work, try using ProcessBuilder. This is my working code:
try {
String phantomJsExe = configuration.getPhantomJsExe().toString();
String phantomJsScript = configuration.getPhantomJsScript().toString();
String urlsTextFile = configuration.getPhantomJsUrlsTextFile().toString();
Process process = new ProcessBuilder(phantomJsExe, phantomJsScript, urlsTextFile).start();
BufferedInputStream bis = new BufferedInputStream(process.getInputStream());
bis.close();
process.waitFor();
} catch (Exception ex) {
ex.printStackTrace();
}
I'm trying to create a program to find all files by a certain name on a Linux server, and then pipe their absolute paths into an ArrayList for processing. My method of using a Process (with exec) and a BufferedReader seems to have worked for all my other needs (various other commands du -h df-h, etc...) however, it doesn't seem to be working in this case in that I get no data outputted! It does seem to be executing as it takes a minute or two to complete but I never see any data result.
Here is the code: (without try/catch which just prints stack trace)
Process process =
Runtime.getRuntime().exec("find " + Main.serversPath + " -name 'dynmap'");
BufferedReader stdInput = new BufferedReader(
new InputStreamReader(process.getInputStream()));
while ((s = stdInput.readLine()) != null) {
filesToDelete.add(s);
if (Main.debugMode == "High") {
System.out.println("Preprocess: dynmap pass - found " + s);
}
}
process.destroy();
You should always capture the error stream of a process in a separate thread (using a StreamGobbler) to handle the cases where the process throws errors.
class StreamGobbler extends Thread
{
private InputStream is;
private String myMessage;
public StreamGobbler(InputStream istream)
{
this.is = istream;
}
public String getMessage()
{
return this.myMessage;
}
#Override
public void run()
{
StringBuilder buffer = new StringBuilder();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
int size = 1024 * 1024;
char[] ch = new char[size];
int read = 0;
try {
while ((read = br.read(ch, 0, size)) >= 0) {
buffer.append(ch, 0, read);
}
}
catch (Exception ioe) {
ioe.printStackTrace();
}
finally {
try {
br.close();
}
catch (IOException e) {
e.printStackTrace();
}
}
this.myMessage = buffer.toString();
return;
}
}
Then you should use the StreamGobbler to capture error stream as follows:
Process process =
new ProcessBuilder("find", Main.serversPath, "-name", "'dynmap'").start();
StreamGobbler error = new StreamGobbler(process.getErrorStream());
error.start();
BufferedReader stdInput =
new BufferedReader(new InputStreamReader(process.getInputStream()));
while ((s = stdInput.readLine()) != null) {
filesToDelete.add(s);
if (Main.debugMode.equals("High")) {
System.out.println("Preprocess: dynmap pass - found " + s);
}
}
// Get the exit status
int exitStatus = process.waitFor();
if (exitStatus != 0) {
// read the error.getMessage() and handle accordingly.
}
process.destroy();
Also, it is recommended to use the ProcessBuilder to create a process.
This line:
System.out.println("Preprocess: dynmap pass - found " + s);
is likely not getting executed.
When used on Strings the == operator compares the object references instead of the values.
In order to compare the actual values you should use the String.equals() method:
if (Main.debugMode.equals("High")) {
System.out.println("Preprocess: dynmap pass - found " + s);
}
See here for an overview of comparing Objects in Java
I think your problem is that you are not closing your BufferedRreader.
You should ALWAYS close and if nesasary, flush your streams.
So:
Process process = Runtime.getRuntime().exec("find " + Main.serversPath + " -name 'dynmap'");
BufferedReader stdInput = new BufferedReader(new InputStreamReader(process.getInputStream()));
while ((s = stdInput.readLine()) != null) {
filesToDelete.add(s);
if (Main.debugMode == "High") {
System.out.println("Preprocess: dynmap pass - found " + s);
}
}
process.destroy();
//Add this line here!
stdInput.close();
You may also want to change this:
if (Main.debugMode == "High") {
System.out.println("Preprocess: dynmap pass - found " + s);
}
to this:
if (Main.debugMode.equals("High")) {
System.out.println("Preprocess: dynmap pass - found " + s);
}
I am working on an application an have an issue about running shell command from java application. here is the code:
public String execRuntime(String cmd) {
Process proc = null;
int inBuffer, errBuffer;
int result = 0;
StringBuffer outputReport = new StringBuffer();
StringBuffer errorBuffer = new StringBuffer();
try {
proc = Runtime.getRuntime().exec(cmd);
} catch (IOException e) {
return "";
}
try {
response.status = 1;
result = proc.waitFor();
} catch (InterruptedException e) {
return "";
}
if (proc != null && null != proc.getInputStream()) {
InputStream is = proc.getInputStream();
InputStream es = proc.getErrorStream();
OutputStream os = proc.getOutputStream();
try {
while ((inBuffer = is.read()) != -1) {
outputReport.append((char) inBuffer);
}
while ((errBuffer = es.read()) != -1) {
errorBuffer.append((char) errBuffer);
}
} catch (IOException e) {
return "";
}
try {
is.close();
is = null;
es.close();
es = null;
os.close();
os = null;
} catch (IOException e) {
return "";
}
proc.destroy();
proc = null;
}
if (errorBuffer.length() > 0) {
logger
.error("could not finish execution because of error(s).");
logger.error("*** Error : " + errorBuffer.toString());
return "";
}
return outputReport.toString();
}
but when i try to exec command like :
/export/home/test/myapp -T "some argument"
myapp reads "some argument" as two seperated arguments.but I want to read "some argument" as only a argument. when i directly run this command from terminal, it executed successfully. I tried '"some argument"' ,""some argument"" , "some\ argument" but did not work for me. how can i read this argument as one argument.
I recall that the an overload of exec method provides a parameter for the arguments seperately. You need to use that
Yup. Here is it
public Process exec(String[] cmdarray)
throws IOException
Just make the command line and all arguments Seperate elements of the String array
first make a string
String cmd="/export/home/test/myapp -T \"some argument\"";
then run cmd in proc