HV-1689 Log an error when a service cannot be loaded

We used to ignore entirely the exception but it can be a legitimate
error.

Unfortunately, we don't have enough information about why this was
ignored in the first place, otherwise we could have tried to use a finer
grained approach.

Author: asutosh936

engine/src/main/java/org/hibernate/validator/internal/util/logging/Log.java

@@ -7,6 +7,7 @@
 package org.hibernate.validator.internal.util.logging;
 
 import static org.jboss.logging.Logger.Level.DEBUG;
+import static org.jboss.logging.Logger.Level.ERROR;
 import static org.jboss.logging.Logger.Level.INFO;
 import static org.jboss.logging.Logger.Level.WARN;
 
@@ -21,6 +22,7 @@
 import java.util.Collection;
 import java.util.List;
 import java.util.Locale;
+import java.util.ServiceConfigurationError;
 import java.util.Set;
 import java.util.regex.PatternSyntaxException;
 
@@ -881,4 +883,8 @@ ConstraintDefinitionException getConstraintValidatorDefinitionConstraintMismatch
 
 	@Message(id = 250, value = "Uninitialized locale: %s. Please register your locale as a locale to initialize when initializing your ValidatorFactory.")
 	ValidationException uninitializedLocale(Locale locale);
+
+	@LogMessage(level = ERROR)
+	@Message(id = 251, value = "An error occurred while loading an instance of service %s.")
+	void unableToLoadInstanceOfService(String serviceName, @Cause ServiceConfigurationError e);
 }

engine/src/main/java/org/hibernate/validator/internal/util/privilegedactions/GetInstancesFromServiceLoader.java

@@ -6,6 +6,10 @@
  */
 package org.hibernate.validator.internal.util.privilegedactions;
 
+import org.hibernate.validator.internal.util.logging.Log;
+import org.hibernate.validator.internal.util.logging.LoggerFactory;
+
+import java.lang.invoke.MethodHandles;
 import java.security.PrivilegedAction;
 import java.util.ArrayList;
 import java.util.Iterator;
@@ -22,6 +26,8 @@ public class GetInstancesFromServiceLoader<T> implements PrivilegedAction<List<T
 
 	private final Class<T> clazz;
 
+	private static final Log LOG = LoggerFactory.make( MethodHandles.lookup() );
+
 	private GetInstancesFromServiceLoader(ClassLoader primaryClassLoader, Class<T> clazz) {
 		this.primaryClassLoader = primaryClassLoader;
 		this.clazz = clazz;
@@ -57,6 +63,8 @@ private List<T> loadInstances(ClassLoader classloader) {
 				// ignore, because it can happen when multiple
 				// services are present and some of them are not class loader
 				// compatible with our API.
+				// log an error still as it can hide a legitimate issue (see HV-1689)
+				LOG.unableToLoadInstanceOfService( loader.getClass().getName(), e );
 			}
 		}
 		return instances;