Hello everybody..
I have a tipical problem.. I need to run a c , java or a command from a
servlet.. I tried using Runtime class as shown below :
.
Runtime rt = Runtime.getRuntime();
Process p = rt.exec("<command / c program>");
. . .
But this code works fine on a stand alone java program.. when i put the
same code inside the servlet.. i don't get even the data from the error
stream..
pls help!
You'll need to drain the standard error and output streams of the Process p.
The following class does this for you: it copies the output of the
process to Java's System.out and System.err. If you need the output for
further processing in your servlet, you'll have to modify method
flush(boolean).
// Begin of OutputAbsorber.java
import java.io.*;
public class OutputAbsorber implements Runnable {
public static void main(String[] args) {
// Example usage
final String command = "cmd.exe /c dir";
try {
Process p = Runtime.getRuntime().exec(command);
OutputAbsorber.absorb(p);
p.waitFor();
} catch (InterruptedException ex) {
ex.printStackTrace();
} catch (IOException ex) {
ex.printStackTrace();
}
}
public static void absorb(Process p) {
if (p != null) {
Thread outAbsorb = new Thread(new OutputAbsorber(
p.getInputStream(), false));
Thread errAbsorb = new Thread(new OutputAbsorber(
p.getErrorStream(), true));
// outAbsorb.setPriority(Thread.MIN_PRIORITY);
// errAbsorb.setPriority(Thread.MIN_PRIORITY);
outAbsorb.start();
errAbsorb.start();
}
}
private final static int MAX_BUF = 512;
private final boolean dropCR;
private final boolean dropNL;
private int limit;
private final byte[] outbuf;
private final InputStream stream;
private final boolean toStdErr;
private OutputAbsorber(InputStream stream, boolean isStdErr) {
this.stream = stream instanceof BufferedInputStream ? stream
: new BufferedInputStream(stream);
this.toStdErr = isStdErr;
this.outbuf = new byte[MAX_BUF];
this.limit = 0;
String lineSeparator = System.getProperty("line.separator");
if ("\n".equals(lineSeparator)) {
this.dropNL = false;
this.dropCR = true;
} else if ("\r".equals(lineSeparator)) {
this.dropNL = true;
this.dropCR = false;
} else {
this.dropNL = false;
this.dropCR = true;
}
}
private int absorb(final int b) {
if (b >= 0) {
switch (b) {
case '\n':
if (!dropNL) {
flush(true);
}
break;
case '\r':
if (!dropCR) {
flush(true);
}
break;
default:
append((byte) b);
break;
}
}
return b;
}
private void append(final byte b) {
if (limit >= MAX_BUF) {
flush(false);
}
outbuf[limit++] = b;
}
private void flush(final boolean addNewline) {
try {
String s = new String(outbuf, 0, limit);
if (toStdErr) {
if (addNewline) {
System.err.println(s);
} else {
System.err.print(s);
}
} else {
if (addNewline) {
System.out.println(s);
} else {
System.out.print(s);
}
}
} finally {
limit = 0;
}
}
private void maybeFlush() {
if (limit > 0) {
flush(true);
}
}
public void run() {
try {
while (absorb(stream.read()) != -1) {
Thread.yield();
}
} catch (IOException ex) {
ex.printStackTrace();
} finally {
try {
stream.close();
} catch (IOException ex) {
ex.printStackTrace();
}
try {
maybeFlush();
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
}
// End of OutputAbsorber.java
