Simplified retrieval of services without types

Author: amitjoy

in.bytehue.messaging.mqtt5.provider/src/main/java/in/bytehue/messaging/mqtt5/provider/helper/MessageHelper.java

@@ -37,6 +37,7 @@
 import java.nio.ByteBuffer;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Comparator;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Optional;
@@ -83,41 +84,43 @@ private MessageHelper() {
 	}
 
 	public static Object getServiceWithoutType(final String clazz, final String filter, final BundleContext context) {
-	    try {
-	        ServiceReference<?>[] references = context.getServiceReferences(clazz, filter);
-	        if (references == null || references.length == 0) {
-	            throw new RuntimeException("'" + clazz + "' service instance cannot be found");
-	        }
-
-	        final ToLongFunction<ServiceReference<?>> srFunc = 
-	            sr -> Optional.ofNullable(((ServiceReference<?>) sr).getProperty(SERVICE_RANKING))
-	                          .filter(Number.class::isInstance)
-	                          .map(Number.class::cast)
-	                          .map(Number::longValue)
-	                          .orElse(0L);
-
-	        return Arrays.stream(references)
-	                     .max(comparingLong(srFunc))  // Finds the reference with the highest ranking
-	                     .map(context::getService)
-	                     .orElseThrow(() -> new RuntimeException("'" + clazz + "' service instance cannot be found"));
-	    } catch (Exception e) {
-	        throw new RuntimeException("Service '" + clazz + "' cannot be retrieved", e);
-	    }
-	}
+        try {
+            ServiceReference<?>[] references = context.getServiceReferences(clazz, filter);
+            
+            if (references == null || references.length == 0) {
+                throw new RuntimeException(String.format("'%s' service instance cannot be found", clazz));
+            }
+
+            return Arrays.stream(references)
+                    .max(Comparator.comparingLong(getServiceRanking()))
+                    .map(context::getService)
+                    .orElseThrow(() -> new RuntimeException(String.format("'%s' service instance cannot be found", clazz)));
+
+        } catch (Exception e) {
+            throw new RuntimeException(String.format("Service '%s' cannot be retrieved", clazz), e);
+        }
+    }
 
-	public static Optional<Object> getOptionalServiceWithoutType(final String clazz, String filter, final BundleContext context, final Logger logger) {
+    public static Optional<Object> getOptionalServiceWithoutType(final String clazz, String filter, final BundleContext context, final Logger logger) {
         try {
-            if (filter.trim().isEmpty()) {
-            	filter = null;
+            if (filter == null || filter.trim().isEmpty()) {
+                filter = null;
             }
-            final Object service = getServiceWithoutType(clazz, filter, context);
-            return Optional.ofNullable(service);
-        } catch (final Exception e) {
-            logger.warn("Service '{}' cannot be retrieved", clazz);
+            return Optional.ofNullable(getServiceWithoutType(clazz, filter, context));
+        } catch (Exception e) {
+            logger.warn("Service '{}' cannot be retrieved", clazz, e);
             return Optional.empty();
         }
     }
 
+    private static ToLongFunction<ServiceReference<?>> getServiceRanking() {
+        return sr -> Optional.ofNullable(sr.getProperty(SERVICE_RANKING))
+                .filter(Number.class::isInstance)
+                .map(Number.class::cast)
+                .map(Number::longValue)
+                .orElse(0L);
+    }
+
 	public static <T> T getService(final Class<T> clazz, final String filter, final BundleContext context) {
 		try {
 			final Collection<ServiceReference<T>> references = context.getServiceReferences(clazz, filter);