 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Java Forum / General / November 2005NoClassDefFoundError
Hi everyone, here I come again with Visual Age for Java troubles. I have created java class that uses JNI and everything is ok when I run my class from command line.What the problem is: when I create the same class using Visual Age I can not run it because of exception: Exception in thread "main" java.lang.NoClassDefFoundError Can anyone tell me what the problem is? Thanks! The NoClassDefFoundError occurs because the JVM can't find the .class file for the program you are trying to run. Usually this is because of the CLASSPATH. But when I write code in Notepad and compile and run it from command line,everything is ok. Problem is, when I write the same code in Visual Age, that is not working.It looks like Visual Age making some troubles. > But when I write code in Notepad and compile and run it from command > line,everything is ok. Problem is, when I write the same code in Visual > Age, that is not working.It looks like Visual Age making some troubles. Yes, and like the previous poster states, that trouble seems to be the classpath. So either fix VAJ classpath, or at least post it here so people can have a clue about what is really wrong. Thank you everyone. I think I've found my error. I think problem is with my header file. From begining: I wrote java code (VAJ 4.0) that uses JNI and compiled it fine.I did't Know how to create header file from VAJ, so I' ve exported my project from VAJ and made header file from command promt using javah -jni command.I wrote native methods in C++ (Visual Studio 6.0). I included java header file and I made dll successfully. In java I called System.loadLibrary to load my dll.First I have tried to run java class file from command line and that was successful try. When I' ve tried to run it from VAJ I got the NoClassDefFoundError. Then I chaged System.loadLibrary with System.load and used absoluth path to my dll. Now I am getting UnsatisfiedLinkError. I' ve searched this forum and I think I have found my error. In my tutorial i read: "The name of the native language function that implements the native method consists of the prefix Java_, the package name, the class name, and the name of the native method." But I don't have the package name in any function name in header file I' ve created, so in my C code, even I have package. So I think it makes me troubles. But I don't know how to fix it, because I am not familiar with VAJ. I hope you can understand my English and what my problem is, and would be very thankfull for any advice. >>Roedy Green >>see http://mindprod.com/jgloss/cac.html I can not open any of links that you posted in this forum?! > I' ve searched this forum and I think I have found my error. In my > tutorial i read: "The name of the native language function that > implements the native method consists of the prefix Java_, the package > name, the class name, and the name of the native method." The rule may be correct but I don't think it's complete. However instead of trying to figure it out yourself, use javah properly and you will get the correct names every time. > But I don't have the package name in any function name in header > file I' ve created, so in my C code, even I have package. When you run javah, you must specify the fully qualified classname (i.e. including the package name). The generated header file will show you exactly how to declare your native methods. E.g.: javah my.package.MyClass ( -jni is no longer necessary ) /gordon  Signature[ do not email me copies of your followups ] g o r d o n + n e w s @ b a l d e r 1 3 . s e Ok, now everything is fine with header file. When I made new header file with package name I also executed my java class file successfully (from command prompt). I am getting just what I've wanted, something like this: Some message from java before calling native.... Native message...from C Some message fro java after calling native... Here we go again VAJ troubles! I can't run the same code from VAJ. Actually, I can run it and it seems like java goes fine but with no C code executing. Result: Some message from java before calling native.... Some message fro java after calling native... I don't know what to do now, because I don't get any error. And I have to use VAJ. Does anyone know what can be wrong? > Here we go again VAJ troubles! I can't run the same code from VAJ. > Actually, I can run it and it seems like java goes fine but with no C [quoted text clipped - 6 lines] > I don't know what to do now, because I don't get any error. And I have > to use VAJ. Does anyone know what can be wrong? First, I don't know VAJ so this is just a guess... Where should printf output (i.e. stdout) go when running from VAJ? I'm guessing you aren't in a console. You didn't get an exception, so my theory is that your native method *is* being called, but you just don't see the output. Try returning a value that the caller can check instead. /gordon Signature[ do not email me copies of your followups ] g o r d o n + n e w s @ b a l d e r 1 3 . s e Thank you Gordon, you were right. VAJ has it's own console and there I can see java answers. Whwn I returned some string from native method to java and print it, I could see it also. So, native method is being called but I can't see the output. Now I have to inform better about VAJ. Thank you everyone! But when I write code in Notepad and compile and run it from command line,everything is ok. Problem is, when I write the same code in Visual Age, that is not working.It looks like Visual Age making some troubles. >NoClassDefFoundError see http://mindprod.com/jgloss/cac.html VAJ was replaced by Eclipse. How come you are still using the code code? SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. > Hi everyone, here I come again with Visual Age for Java troubles. I > have created java class that uses JNI and everything is ok when I run > my class from command line.What the problem is: when I create the same > class using Visual Age I can not run it because of exception: > > Exception in thread "main" java.lang.NoClassDefFoundError Does the exception refer to the class with native methods ? (I assume it does, but you haven't said). What happens if you change the class definition so that it doesn't use native methods (just dummy them out temporarily) or try to load the library ? If that starts to work (it can suddenly find the class with only those changes) then it seems to be a problem with either VAJ's internal JVM not being able to find the DLL (which can be fixed my putting the DLL in the right place -- whereever that might be ;-) or it may be that the internal JVM just isn't able to do JNI. VAJ uses a non-standard JVM implementation which /might/ not support JNI. I can't remember one way or the other, but I wouldn't be /too/ surprised if it didn't -- check the documentation unless you already know for sure that it can. -- chris Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
|
Reply to this Message
|
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2009 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.