从Java Servlet执行时Imagemagick无法打开文件

Question

I'm trying to convert files from png's to pdf using imagemagick and Java. I've got everything working to a place when I'm executing imagemagick command to actually merge multiple png's into one pdf. The command itself looks properly, and it works fine when executed in the terminal but my application gives me error showing that imgck can't open the file (even though it exists and I've set permissions to the folder to 777 :

line: convert: unable to open image `"/Users/mk/Documents/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/sch-java/print-1357784001005.png"': No such file or directory @ error/blob.c/OpenBlob/2642.

This is my command :

/opt/local/bin/convert "/Users/mk/Documents/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/sch-java/print-1357784001005.png" "/Users/mk/Documents/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/sch-java/print-1357784001219.png" "/Users/mk/Documents/workspace/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/sch-java/complete-exportedPanel2013-01-1003:13:17.212.pdf"

And my Java code :

String filesString = "";

for (String s : pdfs){
    filesString += "\""+ s + "\" ";
}

Process imgkProcess = null;

BufferedReader br = null;
File f1 = new File(pdfs[0]);

//returns true
System.out.println("OE: "+f1.exists());

String cmd = imgkPath+"convert "+ filesString+ " \""+outputPath+outName+"\"";
try {
    imgkProcess = Runtime.getRuntime().exec(cmd);
    InputStream stderr = imgkProcess.getErrorStream();
    InputStreamReader isr = new InputStreamReader(stderr);
    br = new BufferedReader(isr);
} catch (IOException e1) {
    msg = e1.getMessage(); 
}

imgkProcess.waitFor();

while( (line=br.readLine() ) != null){
    System.out.println("line: "+line);
}

The whole code is executed from a java servlet controller after getting request from a form. Any ideas what can cause this ? I'm using latest imgck, jdk, and osx 10.7 .

Answer 1

A few things:

• When spawning anything but really trivial processes, it's usually better to use ProcessBuilder than Runtime.exec() - it gives you much better control

• Even with ProcessBuilder, it often works better to write a shell script that does what you need. Then spawn a process to run the script. You get a lot more control in shell script than you do in ProcessBuilder

• Remember that a spawned process is not a shell. It can't, for instance, evaluate expressions, or expand shell variables. If you need that, then you must execute a shell (like sh or bash). Better yet, write a shell script as described above

• If all you need to do is to execute some ImageMagick commands, it would probably be easier to jmagick, a Java interface to ImageMagick - see http://www.jmagick.org/

• Actually, since the you're assembling images into a PDF, the iText library - http://itextpdf.com is probably the best tool for the job, as it is native Java code, does not require spawning a native process, and will therefore be much more portable.

Answer 2

Solved it by adding all arguments to an arrayList and then casting it to String array.

ArrayList<String> cmd = new ArrayList<String>();
cmd.add(imgkPath+"convert");

for (int i=0, l=pdfs.length; i<l; i++){
    cmd.add(pdfs[i]);
}
cmd.add(outputPath+outName);

imgkProcess = Runtime.getRuntime().exec(cmd.toArray(new String[cmd.size()]));