Add prioritized Logging.load() and tests

Introduce LoggingUtils.load() and load(ClassLoader) to return the highest-priority Logging implementation from SPI (uses Prioritized and ServiceLoaderUtils.loadFirstService). Update Javadoc to clarify priority ordering for loadAll, add unit test (testLoad) asserting the prioritized implementation is returned, and set MAX_PRIORITY in TestingLogging by implementing getPriority(). Minor import adjustments.

Author: mercyblitz

microsphere-logging-commons/src/main/java/io/microsphere/logging/DefaultLoggingLevelsResolver.java

@@ -57,4 +57,4 @@ public Set<String> resolve(Class<?> levelClass) {
                 .map(field -> field.getName())
                 .collect(toSet()));
     }
-}
+}

microsphere-logging-commons/src/main/java/io/microsphere/logging/LoggingLevelsResolver.java

@@ -38,4 +38,4 @@ public interface LoggingLevelsResolver {
      */
     @Nonnull
     Set<String> resolve(Class<?> levelClass);
-}
+}

microsphere-logging-commons/src/main/java/io/microsphere/logging/LoggingUtils.java

@@ -19,10 +19,12 @@
 
 import io.microsphere.annotation.Nonnull;
 import io.microsphere.annotation.Nullable;
+import io.microsphere.lang.Prioritized;
 
 import java.util.List;
 
 import static io.microsphere.util.ClassLoaderUtils.getClassLoader;
+import static io.microsphere.util.ServiceLoaderUtils.loadFirstService;
 import static io.microsphere.util.ServiceLoaderUtils.loadServicesList;
 
 /**
@@ -35,17 +37,17 @@
 public abstract class LoggingUtils {
 
     /**
-     * Load all {@link Logging} implementations from SPI
+     * Load all {@link Logging} implementations in priority from SPI
      *
-     * @return
+     * @return non-null
      */
     @Nonnull
     public static List<Logging> loadAll() {
         return loadAll(getClassLoader(LoggingUtils.class));
     }
 
     /**
-     * Load all {@link Logging} implementations from SPI
+     * Load all {@link Logging} implementations in priority from SPI
      *
      * @param classLoader the {@link ClassLoader} which is used to load {@link Logging} implementations
      * @return non-null
@@ -56,6 +58,29 @@ public static List<Logging> loadAll(@Nullable ClassLoader classLoader) throws Il
         return loadServicesList(Logging.class, classLoader, true);
     }
 
+    /**
+     * Load the highest {@link Prioritized priority} {@link Logging} from SPI
+     *
+     * @return non-null
+     * @throws IllegalArgumentException
+     */
+    @Nonnull
+    public static Logging load() throws IllegalArgumentException {
+        return load(getClassLoader(LoggingUtils.class));
+    }
+
+    /**
+     * Load the highest {@link Prioritized priority} {@link Logging} from SPI
+     *
+     * @param classLoader the {@link ClassLoader} which is used to load {@link Logging} implementations
+     * @return non-null
+     * @throws IllegalArgumentException
+     */
+    @Nonnull
+    public static Logging load(@Nullable ClassLoader classLoader) throws IllegalArgumentException {
+        return loadFirstService(Logging.class, classLoader, true);
+    }
+
     private LoggingUtils() {
     }
-}
+}

microsphere-logging-commons/src/test/java/io/microsphere/logging/LoggingUtilsTest.java

@@ -22,8 +22,10 @@
 
 import java.util.List;
 
+import static io.microsphere.logging.LoggingUtils.load;
 import static io.microsphere.logging.LoggingUtils.loadAll;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
 
 /**
  * {@link LoggingUtils}
@@ -40,4 +42,10 @@ void testLoadAll() {
         assertEquals(2, loggings.size());
         assertEquals(loadAll(), loggings);
     }
+
+    @Test
+    void testLoad() {
+        Logging logging = load();
+        assertInstanceOf(TestingLogging.class, logging);
+    }
 }

microsphere-logging-commons/src/test/java/io/microsphere/logging/TestingLogging.java

@@ -70,4 +70,9 @@ public void init(String... loggerNamesAndLevels) {
     public String getName() {
         return "Testing";
     }
+
+    @Override
+    public int getPriority() {
+        return MAX_PRIORITY;
+    }
 }