[GitHub] [arrow] zhztheplayer commented on pull request #7030: ARROW-7808: [Java][Dataset] Implement Datasets Java API by JNI to C++

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zhztheplayer commented on pull request #7030:
URL: https://github.com/apache/arrow/pull/7030#issuecomment-700390598


   Hi @Sebastiaan-Alvarez-Rodriguez ,
   
   First of all, thanks for the detailed explanation about the issue and your suggestions. Sorry for the late reply.
   
   Actually I don't mind to change approach from `System.load` to `System.loadLibrary` as long as it too works fine or even better. I am just worried about why `getResourceAsStream` returns null in your case.
   
   Just saw your practice on compiling Java code:
   
   > cd <project-root>/java/dataset
   > mvn clean install -Dmaven.test.skip=true # skipping tests to let build succeed
   
   Have you checked if arrow_dataset_jni.so was successfully installed within the jar `arrow-dataset-XXX.jar`? If not, specifying `arrow.cpp.build.dir` may helps.
   
   > Maybe it is a good idea to pick one of the following:
   > 1. Change the 'java.io.FileNotFoundException: libarrow_dataset_jni.so' to display the full path (so people know where your library > looks to find the shared object)
   > 2. Make a small JNI_dataset_dev_install_note.md somewhere on getting this library to work.
   > 3. Use System.loadLibrary(libraryToLoad);
   > 4. Use some other way to find the location of a shared library and copy it to a tmpfile
   
   I did a little try and it appears that `System.loadLibrary` requires for property `java.library.path` to be set to include library locations. If we change to use this way, do users have to do this every time before getting started?
   
   I may intend to pick option 1 here. While we should iterate on multiple resource path roots and display several possible paths to let users find in. 


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