Allow C library to be loaded after Nc4Iosp initialization for some cases

netcdf4/src/main/java/ucar/nc2/ffi/netcdf/NetcdfClibrary.java

@@ -32,14 +32,23 @@ public class NetcdfClibrary {
 
   /**
    * Set the path and name of the netcdf c library.
-   * Must be called before load() is called.
+   * <p>
+   * Must be called prior to calling {@link #isLibraryPresent() isLibraryPresent}
+   * or {@link #getForeignFunctionInterface() getForeignFunctionInterface}, as
+   * the C library can only be successfully loaded once.
    *
    * @param jna_path path to shared libraries, may be null. If null, will look for system property
    *        "jna.library.path", then environment variable "JNA_PATH". If set, will set
    *        the environment variable "JNA_PATH".
    * @param lib_name library name, may be null. If null, will use "netcdf".
    */
   public static void setLibraryNameAndPath(@Nullable String jna_path, @Nullable String lib_name) {
+
+    if (nc4 != null) {
+      log.warn("netCDF-C library already set, ignoring.");
+      return;
+    }
+
     lib_name = Strings.emptyToNull(lib_name);
 
     if (lib_name == null) {
@@ -61,6 +70,11 @@ public static void setLibraryNameAndPath(@Nullable String jna_path, @Nullable St
 
     libName = lib_name;
     jnaPath = jna_path;
+
+    if ((isClibraryPresent == null || !isClibraryPresent) && jnaPath != null) {
+      // call load to retry loading, but this time with jnaPath set
+      load();
+    }
   }
 
   /**

netcdf4/src/main/java/ucar/nc2/jni/netcdf/Nc4Iosp.java

@@ -74,16 +74,26 @@ public class Nc4Iosp extends AbstractIOServiceProvider implements IOServiceProvi
   private static final boolean transcodeStrings = Charset.defaultCharset() != StandardCharsets.UTF_8;
 
   /**
-   * set the path and name of the netcdf c library.
-   * must be called before load() is called.
+   * Set the path and name of the netcdf c library.
+   * <p>
+   * This method will only work if the netCDF-C library was not found on the
+   * system path. If you need to use a specific version of the C library, and
+   * you have a different version on a system path, do not use this method.
+   * Instead, call {@link NetcdfClibrary#setLibraryNameAndPath(String, String)
+   * NetcdfClibrary.setLibraryNameAndPath} prior to any uses of
+   * the Nc4Iosp class.
    *
    * @param jnaPath path to shared libraries
    * @param libName library name
    * @deprecated use NetcdfClibrary.setLibraryNameAndPath
    */
   @Deprecated
   public static void setLibraryAndPath(String jnaPath, String libName) {
-    NetcdfClibrary.setLibraryNameAndPath(jnaPath, libName);
+    if (nc4 != null) {
+      log.warn("Library already set, ignoring.");
+    } else {
+      NetcdfClibrary.setLibraryNameAndPath(jnaPath, libName);
+    }
   }
 
   /**