Bootstrap may now return nul for single services.

Bootstrap weas simplified.
Added priority method to bootstrap to enable replacement of bootstrap without any additinional dep.
Removed former ServicePriority (duplicated) annotation.

Author: atsticks

src/main/java/javax/money/MonetaryCurrencies.java

@@ -52,7 +52,7 @@ private static MonetaryCurrenciesSingletonSpi loadMonetaryCurrenciesSingletonSpi
                     () -> new DefaultMonetaryCurrenciesSingletonSpi());
         } catch (Exception e) {
             Logger.getLogger(MonetaryCurrencies.class.getName())
-                    .log(Level.SEVERE, "Failed to load MonetaryCurrenciesSingletonSpi, using default.", e);
+                    .log(Level.INFO, "Failed to load MonetaryCurrenciesSingletonSpi, using default.", e);
             return new DefaultMonetaryCurrenciesSingletonSpi();
         }
     }

src/main/java/javax/money/spi/Bootstrap.java

@@ -111,17 +111,16 @@ public static <T> Collection<T> getServices(Class<T> serviceType) {
      * Delegate method for {@link ServiceProvider#getServices(Class)}.
      *
      * @param serviceType the service type.
-     * @return the service found, never {@code null}.
+     * @return the service found, or {@code null}.
      * @see ServiceProvider#getServices(Class)
      */
     public static <T> T getService(Class<T> serviceType) {
         List<T> services = getServiceProvider().getServices(serviceType);
 		return services
 				.stream()
-				.findFirst()
-				.orElseThrow(
-						() -> new MonetaryException("No such service found: "
-								+ serviceType));
+                .sorted((o1, o2) -> o1.getClass().getSimpleName().compareTo(o2.getClass().getSimpleName()))
+                .findFirst()
+                .orElse(null);
     }
 
 }

src/main/java/javax/money/spi/DefaultServiceProvider.java

@@ -26,6 +26,11 @@ class DefaultServiceProvider implements ServiceProvider {
     /** List of services loaded, per class. */
     private final ConcurrentHashMap<Class, List<Object>> servicesLoaded = new ConcurrentHashMap<>();
 
+    @Override
+    public int getPriority() {
+        return 0;
+    }
+
     /**
      * Loads and registers services.
      *

src/main/java/javax/money/spi/ServiceProvider.java

@@ -20,9 +20,16 @@
  * @author Anatole Tresch
  * @author Werner Keil
  */
-@FunctionalInterface
 public interface ServiceProvider {
 
+    /**
+     * This method allows to define a priority for a registered ServiceProvider instance. When multiple providers are
+     * registered in the system the provider with the highest priority value is taken.
+     *
+     * @return the provider's priority (default is 0).
+     */
+    public int getPriority();
+
 	/**
 	 * Access a list of services, given its type. The bootstrap mechanism should
 	 * order the instance for precedence, hereby the most significant should be
@@ -35,4 +42,17 @@ public interface ServiceProvider {
 	 */
     <T> List<T> getServices(Class<T> serviceType);
 
+    /**
+     * Access a single services, given its type. The bootstrap mechanism should
+     * order the instance for precedence, hereby the most significant should be
+     * first in order and returned. If no such services are found, null is
+     * returned.
+     *
+     * @param serviceType the service type.
+     * @return The instance, (with highest precedence) or {@code null}, if no such service is available.
+     */
+    default <T> T getService(Class<T> serviceType) {
+        return getServices(serviceType).stream().findFirst().orElse(null);
+    }
+
 }

src/test/java/javax/money/spi/BootstrapTest.java

@@ -1,10 +1,5 @@
 package javax.money.spi;
 
-import static org.testng.Assert.assertEquals;
-import static org.testng.Assert.assertFalse;
-import static org.testng.Assert.assertNotNull;
-import static org.testng.Assert.assertTrue;
-
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
@@ -14,6 +9,8 @@
 
 import javax.money.MonetaryException;
 
+import static org.testng.Assert.*;
+
 /**
  * Created by Anatole on 04.03.14.
  */
@@ -65,9 +62,9 @@ public void testGetService() throws Exception {
         assertTrue(num.equals(5));
     }
 
-    @Test(expectedExceptions = {MonetaryException.class})
+    @Test
     public void testGetService_BadCase() throws Exception {
-        Bootstrap.getService(Locale.class);
+        assertNull(Bootstrap.getService(Locale.class));
     }
 
     public final static class TestServiceProvider extends DefaultServiceProvider