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Ecplise Java JNI, java.lang.UnsatisfiedLinkError loading dll

I'm having a problem with loading printer dll. I have a dll file from the printer manufacturer (JniPrinterStatusLib.dll). I wrote code like printer manufacturer suggested. The code is:
package com.printer.test
public class JniPrinterStatus {
static{
System.loadLibrary("JniPrinterStatusLib");
}
public native int GetStatus(String printer);
}
package com.printer.test
public class TestSample {
public static void main(String[] args) {
int status;
String printer = "MY PRINTER";
JniPrinterStatus jps = new JniPrinterStatus();
System.out.println("PRINTER NAME = " + printer);
status = jps.GetStatus(printer);
if (status == -1) {
System.out.println("status = -1");
}
else if (status == 0) {
System.out.println("status = NORMAL");
}
else if ((status & 0x00000080) != 0) {
System.out.println("status = PRINTER_STATUS_OFFLINE");
}
else if ((status & 0x00400000) != 0) {
System.out.println("status = PRINTER_STATUS_DOOR_OPEN");
}
else if ((status & 0x00000010) != 0) {
System.out.println("status = PRINTER_STATUS_PAPER_OUT");
}
else if ((status & 0x00000800) != 0) {
System.out.println("status = PRINTER_STATUS_OUTPUT_BIN_FULL");
}
else if ((status & 0x00000040) != 0) {
System.out.println("status = PRINTER_STATUS_PAPER_PROBLEM");
}
}
}
I used Eclipse to run the code, i put the dll library in the folder project and the error is
PRINTER NAME = MY PRINTER
Exception in thread "main" java.lang.UnsatisfiedLinkError: com.printer.test.JniPrinterStatus.GetStatus(Ljava/lang/String;)I
at com.printer.test.JniPrinterStatus.GetStatus(Native Method)
at com.printer.test.TestSample.main(TestSample.java:10)
If i move the source from the package "com.printer.test" to default package the code works and show:
PRINTER NAME = MY PRINTER
status = -1
I don't know how it's possible. If i compile and run the code from command prompt without package it works.
Where is the problem?
Thank you

From the javadoc for class UnsatisfiedLinkError...
Thrown if the Java Virtual Machine cannot find an appropriate
native-language definition of a method declared native.
That means that function Java_com_printer_test_JniPrinterStatus_GetStatus is not found.
Method loadLibrary in class java.lang.System usually searches the directories listed in the [System] property "java.library.path". For Windows machines, the value of this property is generally the value of the PATH environment variable.
So I suggest printing out the value of that property in your code to see whether it includes the directory containing your DLL. If it doesn't then you need to fix that, either by relocating the DLL or changing the PATH environment variable or launching your java program with the -Djava.library.path=... option. After that you need to check the signature of the native method. Dependency Walker is a tool I use at my work to accomplish this.
EDIT
Having re-read your question, I feel I did not accurately address your question, so let me add...
The default behaviour of Eclipse is to copy resource files, like DLLs, to the output folder. So if you put your DLL in folder src\com\printer\test, it will get copie to folder bin\com\printer\test. My guess is that the current, working directory, i.e. . is in your "java.library.path" which is why it works when your java code is in the default package.

Sorry, actually I wanted to write a comment, but as I'm still low on reputation, I have to try and guess an answer.
There should be no need to recompile the dll - it's just some native code to be invoked.
The java package of the class loading the dll should not make a difference, either.
You have to take care about your system architecture: A 64-bit dll file will fail in a 32-bit JRE and vice versa. Make sure, your JRE architecture matches the dll architecture.
Another thing to take into account is your working directory. Eclipse may use a working directory different from what you used when you ran you program from console.
Last but not least, please have a look at your java.library.path variable.
This page might also help: https://www.chilkatsoft.com/java-loadLibrary-Windows.asp
I covers all the details.

The expected package of the Java classes is hard-coded in the JNI library. In your case, it's the default package.
Let me expand on that. When one implements a native method in a JNI library, one has to create a public C function with a name in the following format:
Java_com_mypackage_MyClass_MyMethod
In other words, the JNI library can't provide methods for the classes in arbitrary packages - only for classes in packages that the JNI library authors had in mind.
In your case, it's the default one. The C function goes Java_JniPrinterStatus_GetStatus. If you call your class MyPrinterStatus, or place it into package com.foobar, the JNI run-time won't be able to associate the C function with the declared Java native method. That's just how JNI was designed.

How to get static final variables using JNA

I am using the GLEW library glew32.dll (standard download from the GLEW website) and I am trying to load the variable GLEW_OK. This variable is defined in the glew.h file (as a uint of 0), so I am assuming it would be included in the glew32.dll file. However, when I use the Java JNA code :
NativeLibrary glew = NativeLibrary.getInstance("glew.dll");
Pointer p = glew.getGlobalVariableAddress("GLEW_OK");
System.out.println(p.getInt(0));
I am given an error of Exception in thread "main" java.lang.UnsatisfiedLinkError: Error looking up 'GLEW_OK': The specified procedure could not be found.
at com.sun.jna.NativeLibrary.getGlobalVariableAddress(NativeLibrary.java:587)
at mcclean.opengl.glew.GLEWUtils.init(GLEWUtils.java:22)
The library is loaded fine, but it appears the static variable could not be found. Why is the static variable not being loaded?

Looking at the header file glew.h, GLEW_OK is found as such:
/* error codes */
#define GLEW_OK 0
This is a preprocessor definition. This is not a "static final variable" as you would conceive in the Java world. When a C++ project is compiled, preprocessor #defines are essentially "copypasted" by the preprocessor into the code. This means that if (val == GLEW_OK) is literally changed into if (val == 0).
Since the preprocessor simply replaces the text, there is no information about the names or the origins of the values originating from defines in the .dll file.
You need to manually find the values. You can do this by downloading the binaries from GLEW and navigating to the include/GL/glew.h file. After this, you could create a class for the constants in Java:
class GlewConstants {
public static final int GLEW_OK = 0;
// ...
}

Java: Protocol Buffer does not generate parsing functions

I've the following .proto file:
message MediatorMessageMsg{
required double speed = 1;
required double heading = 2;
required string sender = 3;
}
and I use Eclipse Mars with Protocol Buffer 2.5.0 version. It generates the necessary file (which we are not supposed to edit) however I cannot use the important functions of
writeDelimitedTo()
parseDelimitedFrom()
newBuilder().set...
without these there is simply no point in using the entire thing. I checked the file and I can see parseDelimitedFrom() there, however I cannot call it in my own project (Yes, imported already). When I hover my mouse on the error, it gives me the following:
The method parseDelimitedFrom(ByteArrayInputStream) is undefined for the type MediatorMessage
Anyone has an idea why is this the case?
EDIT: Some more details regarding the question.
I cannot use the function below, for instance, to build my message. It raises an error.
MediatorMessage mediatorMessage = MediatorMessage.newBuilder().
or I cannot do this
ByteArrayOutputStream output = new ByteArrayOutputStream(bufferSize);
mediatorMessage.writeDelimitedTo(output);
or this
ByteArrayInputStream firstInput = new ByteArrayInputStream(buf);
mediatorMessageOne = MediatorMessage.parseDelimitedFrom(firstInput);
So these functions are not recognized for some reason.

As you still have not answered how your MediatorMessageMsg from the *.proto file becomes MediatorMessage.java find below a stripped down example. Which should point you in the right direction.
Assume following directory and file structure, protoc is assumed to be installed and in your PATH.
bin/
lib/protobuf-java-2.5.0.jar
src/Check.java
MediatorMessage.proto
src/Check.java
import com.google.protobuf.TextFormat;
import sub.optimal.MediatorMessage.MediatorMessageMsg;
class Check {
public static void main(String...args) {
MediatorMessageMsg.Builder builder = MediatorMessageMsg.newBuilder();
MediatorMessageMsg msg = builder.setSpeed(42.0)
.setHeading(0.0)
.setSender("foobar")
.build();
System.out.println(TextFormat.shortDebugString(msg));
}
}
MediatorMessage.proto
option java_package = "sub.optimal";
option java_outer_classname = "MediatorMessage";
message MediatorMessageMsg{
required double speed = 1;
required double heading = 2;
required string sender = 3;
}
generate Java source from proto file
protoc --java_out=src/ MediatorMessage.proto
this generates the Java source file src/sub/optimal/MediatorMessage.java.
compile the Java sources
javac -cp lib/protobuf-java-2.5.0.jar:src/. -d bin/ src/Check.java
this generates the files
bin/Check.class
bin/sub/optimal/MediatorMessage$1.class
bin/sub/optimal/MediatorMessage$MediatorMessageMsg$1.class
bin/sub/optimal/MediatorMessage$MediatorMessageMsg$Builder.class
bin/sub/optimal/MediatorMessage$MediatorMessageMsg.class
bin/sub/optimal/MediatorMessage$MediatorMessageMsgOrBuilder.class
bin/sub/optimal/MediatorMessage.class
run the simple check
java -cp lib/protobuf-java-2.5.0.jar:bin/ Check
output
speed: 42.0 heading: 0.0 sender: "foobar"

Class not found error on Jpype

I have read and searched all stack overflow .. I also found JPype class not found but it didn't help me although it is solved! I have the same problem ! I am using Mac , python 2.7.6
My both python code and A.java are on desktop. But I keep receiving this error :
Traceback (most recent call last): File
"/Users/jeren/Desktop/aa.py", line 13, in
A = jpype.JClass("A") File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/jpype/_jclass.py",
line 54, in JClass
raise _RUNTIMEEXCEPTION.PYEXC("Class %s not found" % name) java.lang.ExceptionPyRaisable: java.lang.Exception: Class A not found
aa.py :
import jpype
import os
jpype.startJVM(jpype.getDefaultJVMPath(), "-ea", "-Djava.class.path=/Users/jeren/Desktop/")
A = jpype.JClass("A")
a = A()
jpype.shutdownJVM()
A.java :
class A
{
public A()
{
super();
}
public String sayHi()
{
return("Hello");
}
public static void main(String[] argv)
{
System.out.println ("Hello ");
}
public static int add(int a, int b)
{
return(a+b);
}
}
My mac , java and python are all 64bit ! where the problem can be?

everything was ok just needed to add a 'public' to the beginning of class A:
public class A
{
public A()
{
super();
}
public String sayHi()
{
return("Hello");
}

Here are some further nodes on specifying the class path for jpype.
A. Check JDK path
I had several versions of Java JDK installed and getDefaultJVMPath did not yield the expected path. I needed to replace
jpype.getDefaultJVMPath()
with the path to the JDK, that actually has been used to compile the code, e.g
D:/jdk11/bin/server/jvm.dll
B. relative paths
It is possible to use relative paths. If my python file is for example in a package folder "pkg" and my java class file is in a sub folder "foo" of a "bin" folder:
parentFolder
pkg/main.py
bin/foo/Foo.class
jpype.startJVM(jvmPath, '-Djava.class.path=../bin")
link = jpype.JClass('foo.Foo')
For this example, the working directory of the java application will be the pkg folder. With other words, inside a main method of Foo class, you might want to use "../" to access the parentFolder.
C. -cp option does not work
I tried to use -cp option instead of -Djava.class.path, which I would found more induitive. However, the following code does not work:
jpype.startJVM(jvmPath, '-cp', classPath)
D. jars need to be included individually
I tried to include a folder with several jar files.
parentFolder
foo/main.py
lib/foo.jar
Following code does not work:
jpype.startJVM(jvmPath, '-Djava.class.path=../lib/*")
link = jpype.JClass('foo.Foo')
Each jar file needs to be included individually, e.g.:
libOath = '../lib'
libJarPaths = str.join(';', [libPath + '/' + name for name in os.listdir(libPath)])
jpype.startJVM(jvmPath, '-Djava.class.path=../lib/*")
link = jpype.JClass('foo.Foo')
(Solution from JPype (Python): importing folder of jar's )

this.getClass().getResource("").getPath() returns an incorrect path

I am currently making a small simple Java program for my Computer Science Final, which needs to get the path of the current running class. The class files are in the C:\2013\game\ folder.
To get this path, I call this code segment in my main class constructor:
public game(){
String testPath = this.getClass().getResource("").getPath();
//Rest of game
}
However, this command instead returns this String: "/" despite the correct output being "C:/2013/game"
Additionally, I attempted to rectify this by using this code:
public game(){
String testPath = this.getClass().getClassLoader().getResource("").getPath();
}
This returns a NullPointerException, which originates from the fact that getClassLoader() returns null, despite working on my Eclipse IDE. Any Ideas?

If you want to load a file in the same path as the code then I suggest you put it in the same root folder as the code and not the same path as the class.
Reason : class can be inside a jar, data file can be put in same jar but its more difficult to edit and update then.
Also suggest you see the preferences class suggested in comments : http://www.javacodegeeks.com/2011/09/use-javautilprefspreferences-instead-of.html though in some cases I think its okay to have your own data/ excel/csv/ java.util.Properties file
Not sure about why it is working in eclipse but I would suggest you focus on running it from a command prompt/ terminal as that is the 'real mode' when it goes live
You could just ask for your class
String s = getClass().getName();
int i = s.lastIndexOf(".");
if(i > -1) s = s.substring(i + 1);
s = s + ".class";
System.out.println("name " +s);
Object testPath = this.getClass().getResource(s);
System.out.println(testPath);
This will give you
name TstPath.class
file:/java/Projects/tests3b/build/classes/s/TstPath.class
Which is my eclipse build path ...
need to parse this to get the path where the class was loaded.
Remember:
App could be started from elsewhere
class can be in jar then path will be different (will point to a jar and file inside that
classpaths can be many at runtime and point 1
a class might be made at runtime via network/ Proxy / injection etc and thus not have a file source, so this is not a generic solution.
think what you want to acheive at a higher level and post that question. meaning why do you want this path?
do you want the app path :-
File f = new File("./");
f.getCanonicalPath();//...
So an app can be started from folder c:\app1\run\
The jar could be at c:\app1\libsMain\myapp.jar
and a helper jar could be at c:\commonlibs\set1
So this will only tell you where the JVM found your class, that may or maynot be what you need.
if inside a jar will give you some thing like this in unix or windows
jar:file:c:\app\my.jar!/s/TstPath.class
If package is s and class is TstPath, you can be sure this will work as the class has to be there ...
now to parse this you can look for your class name and remove / or \ till you get path you want. String lastIndexOf will help

You can use :
URL classURL = getClass().getProtectionDomain().getCodeSource().getLocation();

The call to getResource([String]) requires a path relative to the folder that contains the class it is being called from. So, if you have the following, anything you pass into MyClass.class.getResource([path]); must be a valid path relative to the com/putable/ package folder and it must point to a real file:
package com.putable;
public class MyClass{}
Using the empty string simply isn't valid, because there can never be a file name that equals the empty string. But, you could do getResource(getClass().getSimpleName()). Just remove the file name from the end of the path returned by that call and you will have the class directory you want.

ClassLoader loader = Test.class.getClassLoader();
System.out.println(loader.getResource("Test.class"));
also
Test.class.getProtectionDomain().getCodeSource().getLocation().getPath());

Try this.
import java.io.File;
public class TT {
/**
* #param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
String path = TT.class.getResource("").getPath();
File file = new File(path);
System.out.println(file.getAbsolutePath());
}
}

Try use this code
public game()
{
String className = this.getClass().getSimpleName();
String testPath = this.getClass().getResource(className+".class");
System.out.println("Current Running Location is :"+testPath);
}
visit the link for more information
Find where java class is loaded from

Print out absolute path for a file in your classpath i.e. build/resources/main/someFileInClassPath.txt Disclaimer, this is similar to another solution on this page that used TT.class..., but this did not work for me instead TT..getClassLoader()... did work for me.
import java.io.File;
public class TT {
/**
* #param args
*/
public static void main(String[] args) {
String path = TT.getClassLoader().getResource("someFileInClassPath.txt").getPath();
File file = new File(path);
System.out.println(file.getAbsolutePath());
}
}

Because you used class.getResource(filePath).getpath() in a *.jar file. So the path includes "!". If you want to get content of file in *.jar file, use the following code:
MyClass.class.getResourceAsStream("/path/fileName")