Merge pull request #1474 from lesserwhirls/gh-1473

Fix netCDF-C loading in RuntimeConfigParser

Author: lesserwhirls

cdm/core/src/main/java/ucar/nc2/NetcdfFileWriter.java

@@ -194,7 +194,6 @@ protected NetcdfFileWriter(Version version, String location, boolean isExisting,
     if (version.useJniIosp()) {
       IOServiceProviderWriter spi;
       try {
-        // Nc4Iosp.setLibraryAndPath(path, name);
         Class iospClass = this.getClass().getClassLoader().loadClass("ucar.nc2.jni.netcdf.Nc4Iosp");
         Constructor<IOServiceProviderWriter> ctor = iospClass.getConstructor(Version.class);
         spi = ctor.newInstance(version);

cdm/core/src/main/java/ucar/nc2/util/xml/RuntimeConfigParser.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998-2018 John Caron and University Corporation for Atmospheric Research/Unidata
+ * Copyright (c) 1998-2025 John Caron and University Corporation for Atmospheric Research/Unidata
  * See LICENSE for license information.
  */
 
@@ -269,7 +269,7 @@ public static void read(org.jdom2.Element root, StringBuilder errlog) {
           // so we cannot refer to the Nc4Iosp.class and NetcdfClibrary.class object.
           String nc4IospClassName = "ucar.nc2.jni.netcdf.Nc4Iosp";
           // The setLibraryAndPath method from Nc4Iosp has been deprecated
-          // and splited into separated class: NetcdfClibrary
+          // and split into separated class: NetcdfClibrary
           String netcdfClibraryClassName = "ucar.nc2.ffi.netcdf.NetcdfClibrary";
           /*
            * <Netcdf4Clibrary>
@@ -285,8 +285,9 @@ public static void read(org.jdom2.Element root, StringBuilder errlog) {
           if (path != null && name != null) {
             // reflection is used to decouple optional jars
             try {
-              Class netcdfClibraryClass = RuntimeConfigParser.class.getClassLoader().loadClass(netcdfClibraryClassName);
-              Method method = netcdfClibraryClass.getMethod("setLibraryAndPath", String.class, String.class);
+              Class<?> netcdfClibraryClass =
+                  RuntimeConfigParser.class.getClassLoader().loadClass(netcdfClibraryClassName);
+              Method method = netcdfClibraryClass.getMethod("setLibraryNameAndPath", String.class, String.class);
               method.invoke(null, path, name); // static method has null for object
             } catch (Throwable e) {
               errlog.append(netcdfClibraryClassName + " is not on classpath\n");

docs/src/site/pages/netcdfJava/netcdf4Clibrary.md

@@ -101,7 +101,8 @@ For standalone CDM library use, you can:
 * create a system environment variable: `JNA_PATH=/path/to/library`
 * set a Java property on the command line: `-Djna.library.path=/path/to/library`
 * set the library path and name in the runtime configuration file
-* directly call `Nc4Iosp.setLibraryAndPath()` from your Java program
+* directly call `ucar.nc2.ffi.netcdf.NetcdfClibrary.setLibraryNameAndPath` from your Java program
+  (Note: this must be called prior to calling `isLibraryPresent()` or `getForeignFunctionInterface()` as the C library can only be successfully loaded once)
 
 In all cases, we recommended that you use an absolute path to specify the library location.
 

docs/src/site/pages/netcdfJava_tutorial/runtime/runtimeloading.md

@@ -1,6 +1,6 @@
 ---
 title: Runtime loading
-last_updated: 2021-06-08
+last_updated: 2025-08-12
 sidebar: netcdfJavaTutorial_sidebar
 permalink: runtime_loading.html
 toc: false

netcdf4/build.gradle

@@ -19,6 +19,7 @@ dependencies {
   testImplementation project(':cdm-test-utils')
 
   testImplementation 'com.google.truth:truth'
+  testImplementation 'org.jdom:jdom2'
 
   testRuntimeOnly 'ch.qos.logback:logback-classic'
 }

netcdf4/src/test/java/ucar/nc2/util/xml/TestRuntimeConfigParser.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2025 University Corporation for Atmospheric Research/Unidata
+ * See LICENSE.txt for license information.
+ */
+
+package ucar.nc2.util.xml;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.nio.file.Paths;
+import org.junit.Test;
+
+public class TestRuntimeConfigParser {
+  @Test
+  public void testReflection() throws IOException {
+    // not testing that the loading actually work, but testing that the reflection
+    // calls in the RuntimeConfigParser work
+    File nj22config =
+        Paths.get("src/test/resources/runtimeConfig/nj22Config.xml").toAbsolutePath().normalize().toFile();
+    StringBuilder errlog = new StringBuilder();
+    try (FileInputStream fis = new FileInputStream(nj22config)) {
+      RuntimeConfigParser.read(fis, errlog);
+    }
+    String err = errlog.toString();
+    assertThat(err).isNotEmpty();
+    // since this test lives in the netcdf4 subproject, we should only see
+    // the "is not on classpath" message if the reflection call used in the
+    // RuntimeConfigParser code fails
+    assertThat(err).doesNotContain("is not on classpath");
+  }
+}

netcdf4/src/test/resources/runtimeConfig/nj22Config.xml

@@ -0,0 +1,7 @@
+<nj22Config>
+  <Netcdf4Clibrary>
+    <libraryPath>/not/a/real/path</libraryPath>
+    <libraryName>netcdf</libraryName>
+    <useForReading>false</useForReading>
+  </Netcdf4Clibrary>
+</nj22Config>