use reflection instead of relying on sun.misc.Cleaner being available.

Author: NathanSweet

src/com/esotericsoftware/kryo/util/UnsafeUtil.java

@@ -23,12 +23,12 @@
 
 import java.lang.reflect.Constructor;
 import java.lang.reflect.Field;
+import java.lang.reflect.Method;
 import java.nio.ByteBuffer;
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.List;
 
-import sun.misc.Cleaner;
 import sun.misc.Unsafe;
 import sun.nio.ch.DirectBuffer;
 
@@ -92,6 +92,18 @@ public class UnsafeUtil {
 		_unsafe = tmpUnsafe;
 	}
 
+	static private Method cleanerMethod, cleanMethod;
+	static {
+		try {
+			cleanerMethod = DirectBuffer.class.getMethod("cleaner");
+			cleanerMethod.setAccessible(true);
+			cleanMethod = cleanerMethod.getReturnType().getMethod("clean");
+		} catch (Exception ex) {
+			if (DEBUG) debug("kryo", "No direct ByteBuffer clean method is available.", ex);
+			cleanerMethod = null;
+		}
+	}
+
 	static {
 		ByteBuffer buf = ByteBuffer.allocateDirect(1);
 		try {
@@ -154,11 +166,13 @@ final static public ByteBuffer getDirectBufferAt (long address, int size) {
 	 * 
 	 * NOTE: If Cleaner is not accessible due to SecurityManager restrictions, reflection could be used to obtain the "clean"
 	 * method and then invoke it. */
-	static public void releaseBuffer (ByteBuffer niobuffer) {
-		if (niobuffer != null && niobuffer.isDirect()) {
-			Object cleaner = ((DirectBuffer)niobuffer).cleaner();
-			if (cleaner != null) ((Cleaner)cleaner).clean();
-			niobuffer = null;
+	static public void releaseBuffer (ByteBuffer buffer) {
+		if (!(buffer instanceof DirectBuffer)) return;
+		if (cleanerMethod != null) {
+			try {
+				cleanMethod.invoke(cleanerMethod.invoke(buffer));
+			} catch (Throwable ignored) {
+			}
 		}
 	}
 }