JMuPDF class loading trouble

dubstep · August 19, 2011, 7:02am

Hello all.

I am trying to access the JMuPDF java library from jruby and am having
some trouble. As I am not a Java expert and only have a little
experience accessing java functionality from jruby I was hoping someone
could point out what I am doing wrong.

The JMuPDF library can be found here:

The JMuPDF tutorial I am trying to port to JRuby along with the error
can be read here: Directory contents · GitHub

Requiring the jar file causes no trouble ; it is when I try to actually
use the Java classes that things go wrong.

I have used the same setup with iText without trouble so I am not sure
why it is failing with this one.

Could anyone point out what I am doing wrong? If anyone has any examples
of using JMuPDF from JRuby I would be grateful if they could be shared.

Cheers

Jeff

jeffrey25 · August 20, 2011, 2:33am

You need to use java_import to be able to access the class you are
trying to
access. So after your require statements, do something like this:

java_import ‘com.jmupdf.PdfDocument’
pdf_file = PdfDocument.new(File.read(‘test.pdf’).to_java_bytes)

That should work for you.

jeffrey25 · August 20, 2011, 9:36pm

Actually, since he was using the com.jmupdf.PdfDocument inline he does
not need to do an import (although it is never a bad practice). This
sort of error is usually from one of two things:

Dependent jar on the library you are using is not in the CLASSPATH
You are using some native library that needs java.library.path set.

-Tom

On Fri, Aug 19, 2011 at 7:32 PM, Joseph A. [email protected]
wrote:

I am trying to access the JMuPDF java library from jruby and am having
use the Java classes that things go wrong.

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mail: [email protected]

jeffrey25 · August 22, 2011, 2:25am

Hello all

I went for the full inline call to reduce moving parts in the
application.

The .jar file does rely on a .so / .dll file (pick your poison) so I had
a look at java.library.path and changed the command line invocation to
be:

jruby -J-Djava.library.path=/path/to/dir/with/so/file/in/it/ test.rb

Which, as far as I have read, should make sure that the .so file in that
directory is being picked up. However the same error is still appearing.

As far as I have read from the documentation there are no other
dependencies in terms of Jars. Does anyone have another other ideas /
suggestions?

Cheers

Jeff

jeffrey25 · August 26, 2011, 2:13am

Hello Charles,

Thanks for the suggestions. I should have tried the -d option earlier
but my mind tends to turn off once I am out of ruby-land. I have added
the full output of that command to the gist at

gist.github.com

https://gist.github.com/rurounijones/1156073

Directory contents

-rw-r--r--  1 jjones jjones   45812 2011-08-24 10:05 jmupdf.jar
-rw-r--r--  1 jjones jjones 6912164 2011-08-24 10:05 libjmupdf32.so
-rw-r--r--  1 jjones jjones 7150456 2011-08-24 10:16 libjmupdf64.so
-rw-r--r--  1 jjones jjones 2006604 2011-08-18 13:55 test.pdf
-rw-r--r--  1 jjones jjones     479 2011-10-31 15:38 test.rb

Full Error Output.txt

jruby -d -J-Djava.library.path=/home/jjones/Projects/jmupdftest/ test.rb 
java.lang.ClassNotFoundException: com.jmupdf.PdfDocument
        at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
        at org.jruby.util.JRubyClassLoader.findClass(JRubyClassLoader.java:86)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:247)

This file has been truncated. show original

Pdf_2_BufferedImage.java

# The example file I am working from

package com.examples.convert;

import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

import com.jmupdf.PdfDocument;

This file has been truncated. show original

There are more than three files. show original

Not sure if it is important but the directory I am adding to the
java.library.path has two .so files in it. One for 32bit
(libjmupdf32.so) and one for 64 bit operating systems (libjmupdf64.so),
I am currently on a 64bit Linux.

Thanks

Jeff

jeffrey25 · October 19, 2011, 10:55am

Hello all,

Apologies for dragging up an old thread but I haven’t been able to make
any progress on this and thought I would ask again since my last email
included new information (output from the -d option for a full stack
trace).

I don’t suppose there are any Java guys in the room willing to give it
another look?

cheers

Jeff

jeffrey25 · November 4, 2011, 1:53am

It appeared that the .so files were not being loaded.

Copying the .so files (and the jar, not sure if necessary) into the
linux /lib directory sorted it.

Information here:
https://sourceforge.net/tracker/?func=detail&aid=3430998&group_id=383710&atid=1595531

jeffrey25 · August 25, 2011, 3:49pm

On Sun, Aug 21, 2011 at 7:23 PM, Jeffrey J. [email protected]
wrote:

The .jar file does rely on a .so / .dll file (pick your poison) so I had a
look at java.library.path and changed the command line invocation to be:

jruby -J-Djava.library.path=/path/to/dir/with/so/file/in/it/ test.rb

Which, as far as I have read, should make sure that the .so file in that
directory is being picked up. However the same error is still appearing.

If it is indeed a problem loading the .so, it could be due to JRuby
itself being loaded into the bootstrap classloader. Can you run the
same test with -d? We may be able to get more information out of the
load process, such as the actual error it’s getting loading the class
in question.

Charlie