Load the HDF5 JNI library before enum constants read HDF5Constants

src/main/java/ch/systemsx/cisd/hdf5/CharacterEncoding.java

@@ -16,6 +16,7 @@
 
 package ch.systemsx.cisd.hdf5;
 
+import static ch.systemsx.cisd.hdf5.hdf5lib.HDF5NativeLibrary.intConstant;
 import static hdf.hdf5lib.HDF5Constants.H5T_CSET_ASCII;
 import static hdf.hdf5lib.HDF5Constants.H5T_CSET_UTF8;
 
@@ -26,8 +27,8 @@
  */
 public enum CharacterEncoding
 {
-    ASCII("ASCII", H5T_CSET_ASCII, 1), 
-    UTF8("UTF8", H5T_CSET_UTF8, 4);
+    ASCII("ASCII", intConstant(() -> H5T_CSET_ASCII), 1), 
+    UTF8("UTF8", intConstant(() -> H5T_CSET_UTF8), 4);
 
     private final String charSetName;
 

src/main/java/ch/systemsx/cisd/hdf5/HDF5DataClass.java

@@ -16,6 +16,7 @@
 
 package ch.systemsx.cisd.hdf5;
 
+import static ch.systemsx.cisd.hdf5.hdf5lib.HDF5NativeLibrary.intConstant;
 import static hdf.hdf5lib.HDF5Constants.H5T_BITFIELD;
 import static hdf.hdf5lib.HDF5Constants.H5T_COMPOUND;
 import static hdf.hdf5lib.HDF5Constants.H5T_ENUM;
@@ -47,18 +48,23 @@ public enum HDF5DataClass
 {
     // Implementation note: The order matters! ENUM needs to be before INTEGER, as H5Tdetect_class
     // will return TRUE for ENUM arrays when trying to detect an INTEGER class.
-    BITFIELD(H5T_BITFIELD, new BasicJavaTypeProvider(BitSet.class, null, null, null)), ENUM(
-            H5T_ENUM, new BasicJavaTypeProvider(HDF5EnumerationValue.class,
-                    HDF5EnumerationValueArray.class, null, null)), INTEGER(H5T_INTEGER,
-            new IntJavaTypeProvider()), FLOAT(H5T_FLOAT, new FloatJavaTypeProvider()), STRING(
-            H5T_STRING, new BasicJavaTypeProvider(String.class, String[].class, String[][].class,
-                    MDArray.class)), OPAQUE(H5T_OPAQUE, new BasicJavaTypeProvider(byte.class,
-            byte[].class, byte[][].class, MDByteArray.class)), BOOLEAN(-1,
-            new BasicJavaTypeProvider(boolean.class, BitSet.class, null, null)), COMPOUND(
-            H5T_COMPOUND, new BasicJavaTypeProvider(Map.class, Map[].class, Map[][].class,
-                    MDArray.class)), REFERENCE(H5T_REFERENCE, new BasicJavaTypeProvider(
-            String.class, String[].class, String[][].class, MDArray.class)), OTHER(-1,
-            new BasicJavaTypeProvider(null, null, null, null));
+    BITFIELD(intConstant(() -> H5T_BITFIELD),
+            new BasicJavaTypeProvider(BitSet.class, null, null, null)),
+    ENUM(intConstant(() -> H5T_ENUM),
+            new BasicJavaTypeProvider(HDF5EnumerationValue.class, HDF5EnumerationValueArray.class,
+                    null, null)),
+    INTEGER(intConstant(() -> H5T_INTEGER), new IntJavaTypeProvider()),
+    FLOAT(intConstant(() -> H5T_FLOAT), new FloatJavaTypeProvider()),
+    STRING(intConstant(() -> H5T_STRING),
+            new BasicJavaTypeProvider(String.class, String[].class, String[][].class, MDArray.class)),
+    OPAQUE(intConstant(() -> H5T_OPAQUE),
+            new BasicJavaTypeProvider(byte.class, byte[].class, byte[][].class, MDByteArray.class)),
+    BOOLEAN(-1, new BasicJavaTypeProvider(boolean.class, BitSet.class, null, null)),
+    COMPOUND(intConstant(() -> H5T_COMPOUND),
+            new BasicJavaTypeProvider(Map.class, Map[].class, Map[][].class, MDArray.class)),
+    REFERENCE(intConstant(() -> H5T_REFERENCE),
+            new BasicJavaTypeProvider(String.class, String[].class, String[][].class, MDArray.class)),
+    OTHER(-1, new BasicJavaTypeProvider(null, null, null, null));
 
     /**
      * A role that can provide a java type for a data class, rank and element size.

src/main/java/ch/systemsx/cisd/hdf5/HDF5EnumerationType.java

@@ -16,6 +16,7 @@
 
 package ch.systemsx.cisd.hdf5;
 
+import static ch.systemsx.cisd.hdf5.hdf5lib.HDF5NativeLibrary.longConstant;
 import static hdf.hdf5lib.HDF5Constants.H5T_NATIVE_INT16;
 import static hdf.hdf5lib.HDF5Constants.H5T_NATIVE_INT32;
 import static hdf.hdf5lib.HDF5Constants.H5T_NATIVE_INT8;
@@ -43,15 +44,15 @@ public enum EnumStorageForm
         /**
          * One byte, for up to 255 alternatives.
          */
-        BYTE(1, H5T_NATIVE_INT8, H5T_STD_U8LE),
+        BYTE(1, longConstant(() -> H5T_NATIVE_INT8), longConstant(() -> H5T_STD_U8LE)),
         /**
          * Two bytes, for up to 65535 alternatives.
          */
-        SHORT(2, H5T_NATIVE_INT16, H5T_STD_U16LE),
+        SHORT(2, longConstant(() -> H5T_NATIVE_INT16), longConstant(() -> H5T_STD_U16LE)),
         /**
          * Four bytes, for more than 65535 alternatives.
          */
-        INT(4, H5T_NATIVE_INT32, H5T_STD_U32LE);
+        INT(4, longConstant(() -> H5T_NATIVE_INT32), longConstant(() -> H5T_STD_U32LE));
 
         private final byte storageSize;
 

src/main/java/ch/systemsx/cisd/hdf5/HDF5StorageLayout.java

@@ -1,5 +1,6 @@
 package ch.systemsx.cisd.hdf5;
 
+import static ch.systemsx.cisd.hdf5.hdf5lib.HDF5NativeLibrary.intConstant;
 import hdf.hdf5lib.HDF5Constants;
 
 /**
@@ -9,8 +10,8 @@
  */
 public enum HDF5StorageLayout
 {
-    COMPACT(HDF5Constants.H5D_COMPACT), CONTIGUOUS(HDF5Constants.H5D_CONTIGUOUS), CHUNKED(
-            HDF5Constants.H5D_CHUNKED), NOT_APPLICABLE(-1);
+    COMPACT(intConstant(() -> HDF5Constants.H5D_COMPACT)), CONTIGUOUS(intConstant(() -> HDF5Constants.H5D_CONTIGUOUS)), CHUNKED(
+            intConstant(() -> HDF5Constants.H5D_CHUNKED)), NOT_APPLICABLE(-1);
 
     private int id;
 

src/main/java/ch/systemsx/cisd/hdf5/IHDF5WriterConfigurator.java

@@ -16,6 +16,7 @@
 
 package ch.systemsx.cisd.hdf5;
 
+import static ch.systemsx.cisd.hdf5.hdf5lib.HDF5NativeLibrary.intConstant;
 import hdf.hdf5lib.HDF5Constants;
 
 /**
@@ -71,22 +72,22 @@ public enum FileFormatVersion
         /**
          * The library will create objects with the earliest possible format versions.
          */
-        EARLIEST(HDF5Constants.H5F_LIBVER_EARLIEST, false),
+        EARLIEST(intConstant(() -> HDF5Constants.H5F_LIBVER_EARLIEST), false),
 
         /**
          * The library will allow objects to be created with the latest format versions available to the current library release version.
          */
-        LATEST(HDF5Constants.H5F_LIBVER_LATEST, true),
+        LATEST(intConstant(() -> HDF5Constants.H5F_LIBVER_LATEST), true),
 
         /**
          * The library will allow objects to be created with the latest format versions available to HDF5 v1.8.
          */
-        V1_8(HDF5Constants.H5F_LIBVER_V18, false),
+        V1_8(intConstant(() -> HDF5Constants.H5F_LIBVER_V18), false),
 
         /**
          * The library will allow objects to be created with the latest format versions available to HDF5 v1.10.
          */
-        V1_10(HDF5Constants.H5F_LIBVER_V110, true);
+        V1_10(intConstant(() -> HDF5Constants.H5F_LIBVER_V110), true);
 
         private final int hdf5Constant;
 

src/main/java/ch/systemsx/cisd/hdf5/hdf5lib/HDF5NativeLibrary.java

@@ -1,5 +1,8 @@
 package ch.systemsx.cisd.hdf5.hdf5lib;
 
+import java.util.function.IntSupplier;
+import java.util.function.LongSupplier;
+
 import org.bytedeco.hdf5.hdf5_java;
 import org.bytedeco.javacpp.Loader;
 
@@ -18,6 +21,11 @@
  * public entry points ({@code HDF5Factory}, {@code HDF5FactoryProvider}, {@link HDFHelper}) call it
  * from their static initializers. Code that touches {@code hdf.hdf5lib.H5} directly before any of
  * those should call {@link #load()} itself first.
+ * <p>
+ * Enum constants that are initialized from {@code HDF5Constants} need the same guarantee, but they
+ * are created before any static initializer of their enum runs, and their constructor arguments
+ * are evaluated before their constructor. They read the constant through {@link #intConstant} or
+ * {@link #longConstant} instead, which load the library first.
  */
 public final class HDF5NativeLibrary
 {
@@ -43,12 +51,38 @@ public static synchronized void load()
         {
             return;
         }
-        loaded = true;
-        if (isSet(H5_PATH_PROPERTY) || isSet(H5_NAME_PROPERTY))
+        if (isSet(H5_PATH_PROPERTY) == false && isSet(H5_NAME_PROPERTY) == false)
         {
-            return;
+            // Loader.load() returns null when JavaCPP's library loading is disabled.
+            final String path = Loader.load(hdf5_java.class);
+            if (path != null)
+            {
+                System.setProperty(H5_PATH_PROPERTY, path);
+            }
         }
-        System.setProperty(H5_PATH_PROPERTY, Loader.load(hdf5_java.class));
+        // Only now, so that a failed attempt (e.g. no natives for this platform) is retried and
+        // reported again by the next caller, instead of surfacing later as an obscure
+        // UnsatisfiedLinkError from H5's static initializer.
+        loaded = true;
+    }
+
+    /**
+     * Returns {@code constant.getAsInt()}, after {@link #load()}. For initializing enum constants
+     * from {@code HDF5Constants}, e.g. {@code COMPACT(intConstant(() -> H5D_COMPACT))}.
+     */
+    public static int intConstant(IntSupplier constant)
+    {
+        load();
+        return constant.getAsInt();
+    }
+
+    /**
+     * Returns {@code constant.getAsLong()}, after {@link #load()}. See {@link #intConstant}.
+     */
+    public static long longConstant(LongSupplier constant)
+    {
+        load();
+        return constant.getAsLong();
     }
 
     private static boolean isSet(String key)