fix: expect contextClassLoader to be null

Thread.currentThread().getContextClassLoader() may be null

delight-core/src/main/java/de/dfki/delight/Delight.java

@@ -27,6 +27,8 @@ import de.dfki.delight.common.ParameterConversionManager;
 import de.dfki.delight.di.GuiceUtils;
 import de.dfki.delight.transport.MethodCallSender;
 
+import static de.dfki.delight.server.util.ClassLoaderUtil.getContextClassLoader;
+
 /**
  * Client part of delight. - allows to connect to some host and to use specific
  * apis
@@ -180,8 +182,7 @@ public class Delight {
 
 	public <API> API usingApi(final String handlerName, final Class<API> apiClass, final Class<?>[] parameterTypes,
 		final Object[] baseCtorArgs) {
-	    return usingApi(handlerName, apiClass, parameterTypes, baseCtorArgs,
-		    Thread.currentThread().getContextClassLoader());
+	    return usingApi(handlerName, apiClass, parameterTypes, baseCtorArgs, getContextClassLoader());
 	}
 
 	public <API> API usingApi(final String handlerName, final Class<API> apiClass, final Class<?>[] parameterTypes,

delight-core/src/main/java/de/dfki/delight/DelightConfigFinder.java

 package de.dfki.delight;
 
+import static de.dfki.delight.server.util.ClassLoaderUtil.getContextClassLoader;
+
 import java.io.IOException;
 import java.net.URL;
 import java.util.Enumeration;
@@ -30,7 +32,7 @@ public class DelightConfigFinder {
 	DelightConfigBuilder defaultConfig = null;
 	Class<? extends ConfigProvider> defaultConfigProviderClass = null;
 	String defaultLocation = null;
-	ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
+	ClassLoader classLoader = getContextClassLoader();
 	try {
 	    Enumeration<URL> resources = classLoader.getResources(DEFAULT_CONFIG_RESOURCE);
 	    if (!resources.hasMoreElements()) {

delight-core/src/main/java/de/dfki/delight/server/util/ClassLoaderUtil.java

+package de.dfki.delight.server.util;
+
+public class ClassLoaderUtil {
+    /**
+     * Get the current thread's context ClassLoader. If it is null, the ClassLoader of this class is used.
+     */
+    public static ClassLoader getContextClassLoader() {
+        ClassLoader cl = Thread.currentThread().getContextClassLoader();
+        if (cl == null) {
+            cl = ClassLoaderUtil.class.getClassLoader();
+        }
+        return cl;
+    }
+}
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