[LOGGING-186] Replace custom code with ServiceLoader call (#171)

* Replace custom code with `ServiceLoader` call

* Files should end with an empty line

* Files should end with an empty line

* Comment empty block

* Comment empty block

---------

Co-authored-by: Gary Gregory <garydgregory@users.noreply.github.com>

src/test/java/org/apache/commons/logging/serviceloader/ServiceLoaderTestCase.java

@@ -0,0 +1,30 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.commons.logging.serviceloader;
+
+import junit.framework.TestCase;
+import org.apache.commons.logging.LogFactory;
+import org.apache.commons.logging.serviceloader.internal.DummyLogFactory;
+
+public class ServiceLoaderTestCase extends TestCase {
+
+    public void testServiceLoader() {
+        final LogFactory factory = LogFactory.getFactory();
+        assertTrue("Wrong factory retrieved through ServiceLoader: " + factory.getClass().getName(),
+                factory instanceof DummyLogFactory);
+    }
+}

src/test/java/org/apache/commons/logging/serviceloader/internal/DummyLogFactory.java

@@ -0,0 +1,58 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.commons.logging.serviceloader.internal;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogConfigurationException;
+import org.apache.commons.logging.LogFactory;
+
+public class DummyLogFactory extends LogFactory {
+    @Override
+    public Object getAttribute(String name) {
+        return null;
+    }
+
+    @Override
+    public String[] getAttributeNames() {
+        return new String[0];
+    }
+
+    @Override
+    public Log getInstance(Class clazz) throws LogConfigurationException {
+        return null;
+    }
+
+    @Override
+    public Log getInstance(String name) throws LogConfigurationException {
+        return null;
+    }
+
+    @Override
+    public void release() {
+        // empty
+    }
+
+    @Override
+    public void removeAttribute(String name) {
+        // empty
+    }
+
+    @Override
+    public void setAttribute(String name, Object value) {
+        // empty
+    }
+}

src/test/java/org/apache/commons/logging/serviceloader/internal/ThrowingLogFactory.java

@@ -0,0 +1,25 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.commons.logging.serviceloader.internal;
+
+/**
+ * A common ServiceLoader error is finding a class that implements LogFactory from a different classloader.
+ * This class should emulate that behavior.
+ */
+public class ThrowingLogFactory {
+  // empty
+}