Question

UnsatisifedLinkError with JNI

Asked by: letharion

I have
libBoincResolve.so
and base/Connector.class

Connector.class
has
public static native String BoincResolve(String filename);
and does
System.loadLibrary("BoincResolve");
BoincResolve("in");

When "BoincResolve" executes, I get:
Exception in thread "main" java.lang.UnsatisfiedLinkError: base.Connecter.BoincResolve(Ljava/lang/String;)Ljava/lang/String;

I can see that it's trying to find BoincResolve inside base.Connector, but I'm not sure why that is, and thus not what I can do about it either.

Please advise. Let me know if more information is necessary.

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Asked On
2009-11-04 at 08:49:15ID24871494
Topics

Java Native Interface (JNI)

,

New to Java Programming

,

Java Programming Language

Participating Experts
4
Points
500
Comments
10

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Answers

 

by: dravidnsrPosted on 2009-11-04 at 09:13:00ID: 25741533

 

by: CEHJPosted on 2009-11-04 at 09:31:22ID: 25741724

That error message refers to a method that takes a String *array*, not a String. Make sure your java and native code are in sync, and that the library is in java.library.path

http://technojeeves.com/joomla/index.php/free/54-javasystemproperties

 

by: a_bPosted on 2009-11-04 at 09:45:41ID: 25741856

Are you setting the java.library.path correctly?

 

by: letharionPosted on 2009-11-04 at 10:06:47ID: 25742058

dravidnsr: Thanks, will have a look at them

CEHJ: I don't see that array, could you elaborate? If that was the case, then would the problem be in
public static native String BoincResolve(String filename); ?

a_b:
java -Djava.library.path=/home/letharion/GTBoinc/SQLdb/base/ -cp :/usr/share/jdbc-mysql/lib/jdbc-mysql.jar:./ta-lib.jar base.Connecter

executed from /home/letharion/GTBoinc/SQLdb/
libBoincResolve.so is in both SQLdb/ and base/

 

by: CEHJPosted on 2009-11-04 at 10:24:28ID: 25742227

I would rebuild your native code to be on the safe side. Make sure your packaging is right too

 

by: jb1devPosted on 2009-11-04 at 12:08:36ID: 25743378

> That error message refers to a method that takes a String *array*, not a String.

If this were the case, I would expect to see a "[" in the signature for the parameter right?
I see only
L<fully qualified class name>
Which I would expect to be a String.

See Type Signatures:
http://java.sun.com/j2se/1.5.0/docs/guide/jni/spec/types.html

Is this on a *nix platform? Is LD_LIBRARY_PATH set correctly?


 

by: jb1devPosted on 2009-11-04 at 12:14:24ID: 25743439

Does
ldd /path/to/your/so/libBoincResolve.so
show undefined symbols?
If so, might need to add some switches when linking to specify additional resources are linked properly.




 

by: CEHJPosted on 2009-11-04 at 13:28:03ID: 25744138

>>If this were the case, I would expect to see a "[" in the signature for the parameter right?

Yes - you're right - sorry - misread it

 

by: letharionPosted on 2009-11-05 at 01:27:22ID: 25747830

>I would rebuild your native code to be on the safe side.

This turned out to be the issue. First I build a nativetest project separately from everything else, it worked well. When integrating with the rest of my code, I got this problem. Upon closer examination, it turns out that the header file for c code was incorrect. I had manually updated what I thought was the important parts, but when I created a new header with javah, I noticed that the new header file has a signature with
(JNIEnv *, jclass, jstring), where the old had (JNIEnv *, jobject, jstring)

Not sure why one wants a class and one an object, but that was it.
Lesson learned, make javah -jni part of the build process.

 

by: CEHJPosted on 2009-11-05 at 03:58:01ID: 25748552

:-)

20120131-EE-VQP-002

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