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Version 6.1 by Pascal Robert on 2012/08/11 18:16
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1 = The Project Wonder way =
2
3 Project Wonder, in the ERExtensions framework, have a utility class to help you run command-line applications, [[ERXRuntimeUtilities>>http://jenkins.wocommunity.org/job/Wonder/javadoc/er/extensions/foundation/ERXRuntimeUtilities.html]]. This utility class is used inside Wonder, for example ERAttachment use it to call ImageMagick when you want to resize images.
4
5 Check the Javadoc for the [[execute>>http://jenkins.wocommunity.org/job/Wonder/javadoc/er/extensions/foundation/ERXRuntimeUtilities.html#execute]] method to see examples.
6
7 = The Java way =
8
9 Here, the "cat" and "outputCat" are debugging output categories:
10
11 {{code}}
12
13 Process process=null;
14 try {
15 process = Runtime.getRuntime().exec(commandLine);
16 OutputStream output = process.getOutputStream();
17 output.write(inputString.getBytes());
18 output.close();
19 process.waitFor();
20 DataInputStream dis=new DataInputStream(process.getInputStream());
21 String output;
22 do {
23 output = dis.readLine();
24 if (output != null)
25 outputCat.debug(output);
26 } while (output != null);
27 dis.close();
28 } catch (IOException e) {
29 cat.error("IOException: " + e.toString());
30 } catch (InterruptedException e) {
31 cat.error("Interrupted process: " + e.toString());
32 } finally {
33 if (process != null)
34 process.destroy();
35 outputCat.debug("Process finished.");
36 }
37
38 {{/code}}
39
40 Note: A number of people have reported problems with process.waitFor() on Windows. The WebObjects Development List at Omnigroup has a number of people's workaround code for this problem.
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42 **Note 2:** The procedure given here, of course, is to call anything executable from the command line from your Java program, not just Perl scripts.
43
44 === Mike Schrag ===
45
46 process.waitFor() is not just a problem on Windows. This code //will// cause problems. Process maintains buffers for stdout and stderr. If you do not consume those streams, you will run into deadlocks. The proper way to use Runtime.exec is to setup a thread for stderr and a thread for stdout and consume them yourself into your own buffer that does not have the same restrictions that the stock VM has.
47
48 There's a good example of this technique on [[JavaWorld>>http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html]].