I'm trying to run a piece of sample code to connect to a specific DVR. I've got the SDK from the DVR manufacturer. The code tries to call a native library like this:
DHNetSDKLib INSTANCE = (DHNetSDKLib)Native.loadLibrary("dhnetsdk", DHNetSDKLib.class);
But, no matter where I put the dll file, I always get this error:
Exception in thread "main" java.lang.UnsatisfiedLinkError: Unable to load library 'dhnetsdk': Specified module could not be found.
This being a piece of demo code, I feel this should work. The dll files are placed in the root folder as standard. I've tried copying them to the windows dll folders, gave them a folder of their own (C:\dll), adding this folder to the PATH variable, editing project properties to include the various folders to the build path, pointing to it like this:
DHNetSDKLib INSTANCE = (DHNetSDKLib)Native.loadLibrary("C:\\dll\\dhnetsdk.dll", DHNetSDKLib.class);
But nothing works. I've searched a lot but I have yet to find a solution. Most threads I come across however usually don't have the module bit in the error. Perhaps there is something wrong with the dll?
I'm trying to do this in java because I want to build an Android application using this dll, but now I'm wondering if that is even possible. The only search results I find are related to native Android code (I think). This project is being run as a standard application for testing purposes however.
Related
I am trying to build a small personal project with opencv. I included the path to the opencv jar file in visual studio using the java dependencies then referenced libraries but i get the linker error: Exception in thread "main" java.lang.UnsatisfiedLinkError: no opencv_java430 in java.library.path. I have no idea what else i could do
UnsatisfiedLinkError isn't about jar files.
It's about 'native' files. These are generally stored as a .jnilib file on mac, as a .DLL on windows, and as a .so file on on most unixen.
They cannot be in jar files.
Some libraries will put in some effort and ship a whole bevy of them (as each architecture and OS has a unique dll/jnilib/so file that is needed) inside the jar, will find the 'right' one for your arch/os combo, unpack it someplace, and try to load it live.
This is either not working, or this library isn't doing that. Presumably the opencv site contains a tutorial on how to get it running; as native files are required, it's a bit more involved than 'just download, add to classpath, and voila'. I suggest you follow it precisely.
If you do have something that seems suitable (probably called opencv_java430.dll or whatnot), start java with java -Djava.library.path=/directory/containing/that/file the.rest.of.your.java.args - that should help.
I'm trying to do some template matching with the Java binding of OpenCV 4.3.0 in Eclipse, but attempting to load the template image always results in this error:
Exception in thread "main" java.lang.UnsatisfiedLinkError: org.opencv.imgcodecs.Imgcodecs.imread_0(Ljava/lang/String;I)J
The line of code where this exception is thrown is this:
flowerTemplate = Imgcodecs.imread("/templates/flowerpot_white.png", Imgcodecs.IMREAD_COLOR);
I have tried a number of solutions suggested on similar questions on StackOverflow and elsewhere on the internet, including:
Pointing at the native library folder with the "Native library location" variable in the user library definition in Eclipse.
Adding the native library folder location to my PATH variable.
Adding the native library .dll location to my PATH variable.
Setting up the Eclipse run configuration to add the native library folder & .dll locations to the PATH and CLASSPATH variables.
Loading the library with the appropriate Java code, in each of the three ways I saw it suggested, in three different places which all run before the code that throws the exception.
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
System.load(<path_to_the_dll>);
File opencvLibrary = new File(System.mapLibraryName(Core.NATIVE_LIBRARY_NAME));
System.load(opencvLibrary.getAbsolutePath());
Placing the .dll in question into my source folder and every subfolder. I am running it from within Eclipse, so this is also the program's working directory.
UnsatisfiedLinkError is a runtime exception that happens when running your Java program. So placing your file in the source folder will not work.
You need it to be available in a place that your program can find it.
See this article for example:
https://www.javaworld.com/article/2077520/java-tip-23--write-native-methods.html
In it they place the library in Linux's library path. In windows you'd similarly place it in the current directory (where you're running from) or in some shared location.
This article explains Window's dll search order: https://learn.microsoft.com/en-us/windows/win32/dlls/dynamic-link-library-search-order
You shouldn't need to explicitly call System.loadLibrary() yourself. That's the library's responsibility.
Your problem is that OpenCV is improperly installed on your machine or inaccessible from Eclipse.
For instructions on how to make in work in Eclipse see:
Add .dll to java.library.path in Eclipse/PyDev Jython project
After removing every load method and then adding them back one-by-one, I determined that the issue was most likely caused by Eclipse loading the native library folder twice.
I've found a bunch of Stack Overflow Questions and Answers, but so far I haven't found any that work for me. I am trying to make an executable jar in Eclipse from a program which requires an extra jar and a dll. The way I got this to work properly in Eclipse is by configuring the Build Path as shown in
this image. The hierarchy of the project is this. I've tried messing with the Manifest file a bit, but I haven't made any progress with that.
I've been running the jar by using java -jar /path/to/jar and I keep getting an error saying Exception in thread "main" java.lang.NoClassDefFoundError: com/jacob/activeX/ActiveXComponent .... I've tried defining a path to the jar using -Djava.library.path=/path/to/jar and I get an error saying Error: Could not find or loaded main class outlook_dl_2.jar.
Is there any way to solve this without using a third-party application like One JAR? That's the only thing I can find that I haven't tried and I'm trying to avoid it if possible, since I feel like it really shouldn't be necessary. I'll use it as a worst-case scenario, but I would like to get this working without it.
Anyone know what I'm doing wrong here?
I'm a little confused by this error. I'm new to Java and the error seems pretty self explanatory, but I've checked my paths (even defined my own) and it still fails to find this library. Is there something I'm doing wrong? See directory screenshot and error screenshot below:
UPDATE
UPDATE 2
If I create a new NetBeans project this works fine. Same code and everything. If I create new IntelliJ project I get this error above. I must be missing something in IntelliJ
UPDATE 3
Found the solution. Adding dependencies is a bit different in IntelliJ. Thanks all for the help.
http://www.jetbrains.com/idea/webhelp/configuring-module-dependencies-and-libraries.html
Obidisc4j is a .jar file. You just dont see its extension in the explorer.
Regular jar files are not loaded by System.loadLibrary. They are automatically loaded by the JVM's classLoader.
You are using a native library. It doen't matter if that library is in the classpath. There are 4 ways you can make the Java runtime load your shared library at runtime:
Call System.load to load the .so from an explicitly specified absolute path.
Copy the shared library to one of the paths already listed in java.library.path
Modify the LD_LIBRARY_PATH environment variable to include the directory where the shared library is located.
Specify the java.library.path on the command line by using the -D option.
Seems like your application is trying to find out a obidisc4j.dll (for Windows) or obidisc4j.so (for Linux). The file must be present on the PATH (but not the classpath). If you are not sure what PATH is your Java application searching in, you can write the following statement, before the point where the exception takes place, to find out the PATH.
System.out.println(System.getProperty("java.library.path"));
This will tell you about the paths where your DLL or SO file should be placed. You just need to place the file in ONE of those N-paths.
(It might be an obvious mistake I'm making, but I couldn't get it to work after 6 hours now.)
I'm trying to get CPU information using the sigar.jar in my eclipse project (just testing the sigar API for now).
It runs in eclipse without problems:
what made it work in eclipse was to put the dll in the same folder as
the sigar.jar
I tested that adding a path to the dll as the "native code property"
in the build path config dialog has no effect.
Adding vm arguments in the run configuration also has no effect.
I tested putting 2 fake paths in those 2 places and as long as I have the
dll in the same folder as the sigar.jar... it runs well in eclipse.
The problem is when I try to export a runnable .jar file for my project. I tried 2 things:
I modified the MANIFEST.MF file with Bundle-NativeCode: libs/sigar-amd64-winnt.dll (I'm assuming here the path is relative to the project folder) --> no success:
main starting!! no sigar-amd64-winnt.dll in java.library.path
org.hyperic.sigar.SigarException: no sigar-amd64-winnt.dll in
java.library.path
at org.hyperic.sigar.Sigar.loadLibrary(Sigar.java:172)
at org.hyperic.sigar.Sigar.<clinit>(Sigar.java:100)
at CpuData.main(CpuData.java:59)
cpudata(sigar s) starting!!! cpuInfo() starting!!!
Exception in thread
"main" java.lang.UnsatisfiedLinkError:
org.hyperic.sigar.Sigar.getCpuInfoList()[Lorg/hyperic/sigar/C puInfo;
at org.hyperic.sigar.Sigar.getCpuInfoList(Native Method)
at CpuData.cpuInfo(CpuData.java:103)
at CpuData.<init>(CpuData.java:29)
at CpuData.main(CpuData.java:59)
Then I decided to put the .dll in the same folder as my project.jar, and used in the command line: java -Djava.library.path=./native/ -jar C:\cpu_usage_log\cpu3.jar (I'm assuming here the path is relative to the folder that contains the project.jar) ...but again no success:
Error: impossible to find or load the main class .library.path=..native
(I suspected that I should give a main class name as a second argument after the -Djava.library.path=./path/ but I can't find that supposed "main class" name, or any examples on the web that do specify such a class ...is it a main class from within the .dll?)
I don't really know what else to try at this point. I read those 2 solutions worked for others, and it makes it even more frustrating because I imagine it could something obvious that I missed or didn't understand when reading other posts and that I just can't find (it's the first time I deal with native dlls in a java project).
For me it was always the best to modify the way how Java loads the library.
Usually you call System.loadLibrary("mylib"); which searches the library on the library path.
IMHO it is much better loading the library using it's absolute path. This allows you to implement a custom search logic in your program:
// Extends the name to mylib.so or mylib.dll
mylibname = System.mapLibraryName("mylib");
// Load the library via its absolute path
System.load(new File(path, mylibname).getAbsolutePath());
Note that each library can only be loaded once, therefore if you load the library as shown above, calls of System.loadLibrary("mylib"); afterwards will be ignored as the library is already loaded.