Add troubleshoting indication based on https://github.com/OSGeo/proj.4/issues/380 comments.

1 files changed, 14 insertions, 3 deletions

diff --git a/jniwrap/README.md b/jniwrap/README.md
index 3a6b35be..e5748cda 100644
--- a/jniwrap/README.md
+++ b/jniwrap/README.md
@@ -101,9 +101,9 @@ Of course, real applications would read them from a file or other data source.
 
 
 
-### compile the Main code
+### Compile the Main code
 
-we assume that PROJ was compiled with the right flag to support the bridge to Java
+We assume that PROJ was compiled with the right flag to support the bridge to Java.
 Therefore we have a library called `proj.jar`.
 Thus we compile the `Main.java` with the command:
 
@@ -113,4 +113,15 @@ and execute the created test case with:
 
     java --class-path .:<path to the jar library>/proj.jar -Djava.library.path=<path to the libproj, if needed> Main
 
-That's it, enjoy!
+
+
+### Troubleshooting
+
+If an `java.lang.UnsatisfiedLinkError` is thrown at execution time, add the following line in the Java code:
+
+    System.out.println(System.getProperty("java.library.path"));
+
+Then verify that the `libproj.so` (Linux), `libproj.dylib` (MacOS) or `libproj.dll` (Windows) file is located
+in one of the directories listed by above code. If this is not the case, then try configuring the
+`LD_LIBRARY_PATH` (Linux), `DYLD_LIBRARY_PATH` (MacOS) or `PATH` (Windows) environment variable.
+If the problem persist, adding the `-verbose:jni` option to the `java` command may help more advanced diagnostics.