Refactor: apply best practices and coding guidelines globally (OpenEMS#2209)

The PR contains strictly **NO LOGIC CHANGES**, but applies best practices and coding guidelines (https://openems.github.io/openems.io/openems/latest/contribute/coding-guidelines.html) globally in OpenEMS Edge/Backend, e.g.

- Use separate Interface and Implementation files for OpenEMS Edge Components
- Move ChannelIds to Interfaces ("Natures" - https://openems.github.io/openems.io/openems/latest/coreconcepts.html#_nature)
- Rename Component files equal to Factory-ID (makes Ctrl+R in Eclipse IDE much more convenient to use)
- Reduce variable scope; use `private` wherever possible (e.g. for the `activate()`-method). This is enforced by adding and applying Checkstyle `VisibilityModifierCheck` (see https://checkstyle.sourceforge.io/apidocs/com/puppycrawl/tools/checkstyle/checks/design/VisibilityModifierCheck.html)
- Sort variables in code (from `public static final` to `private`; @reference to constructor to @activate, @Modifed, @deactivate)
- Use short JavaDoc for single-line comments
- Use `@EventTopics`
- Always implement @deactivate
- Remove `package-info.java` if not necessary (i.e. reduce package scope)
- Add (at least simple) JUnit tests
- Update BND Bundle templates

Author: sfeilmeier

cnf/checkstyle.xml

@@ -188,7 +188,9 @@
       <message key="name.invalidPattern" value="Method name ''{0}'' must match pattern ''{1}''."/>
     </module>
     <module name="SingleLineJavadoc">
+      <property name="severity" value="ignore"/>
       <property name="ignoreInlineTags" value="false"/>
+      <metadata name="net.sf.eclipsecs.core.lastEnabledSeverity" value="inherit"/>
     </module>
     <module name="EmptyCatchBlock">
       <property name="exceptionVariableName" value="expected"/>
@@ -206,6 +208,11 @@
       <property name="ignoreMethodNamesRegex" value="doc|set.+|build"/>
       <property name="tokens" value="METHOD_DEF"/>
     </module>
+    <module name="VisibilityModifier">
+      <property name="protectedAllowed" value="true"/>
+      <property name="allowPublicFinalFields" value="true"/>
+      <property name="allowPublicImmutableFields" value="true"/>
+    </module>
   </module>
   <module name="LineLength">
     <property name="severity" value="ignore"/>

io.openems.backend.alerting/src/io/openems/backend/alerting/Alerting.java

@@ -41,8 +41,9 @@ public class Alerting extends AbstractOpenemsBackendComponent implements EventHa
 	private static final byte THREAD_POOL_SIZE = 2;
 	private static final byte THREAD_QUEUE_WARNING_THRESHOLD = 50;
 
-	private final Logger log = LoggerFactory.getLogger(Alerting.class);
+	protected final Scheduler scheduler;
 
+	private final Logger log = LoggerFactory.getLogger(Alerting.class);
 	private final ThreadPoolExecutor executor;
 
 	@Reference
@@ -51,7 +52,6 @@ public class Alerting extends AbstractOpenemsBackendComponent implements EventHa
 	@Reference
 	protected Mailer mailer;
 
-	protected final Scheduler scheduler;
 	protected Handler<?>[] handlers = {};
 
 	protected Alerting(Scheduler scheduler) {

io.openems.backend.alerting/test/io/openems/backend/alerting/AlertingTest.java

@@ -79,7 +79,7 @@ public void testHandleEvent() {
 
 	/* ********** */
 	static class DummyAlerting extends Alerting {
-		Event lastEvent;
+		private Event lastEvent;
 
 		public DummyAlerting() {
 			super.metadata = new DummyMetadata();

io.openems.backend.alerting/test/io/openems/backend/alerting/Dummy.java

@@ -21,8 +21,9 @@
 import io.openems.backend.common.test.DummyMetadata;
 
 public class Dummy {
+
 	public static class MailerImpl implements Mailer {
-		public Map<ZonedDateTime, String> sentMails = new HashMap<>();
+		public final Map<ZonedDateTime, String> sentMails = new HashMap<>();
 
 		@Override
 		public void sendMail(ZonedDateTime sendAt, String template, JsonElement params) {
@@ -67,8 +68,8 @@ public EventAdmin getEventAdmin() {
 	}
 
 	public static class MetadataImpl extends SimpleMetadataImpl {
-		public List<Edge> edges;
-		public Map<String, List<AlertingSetting>> settings;
+		private List<Edge> edges;
+		private Map<String, List<AlertingSetting>> settings;
 
 		/**
 		 * Initialize Metadata with test data.
@@ -86,6 +87,10 @@ public boolean isInitialized() {
 			return true;
 		}
 
+		public Map<String, List<AlertingSetting>> getSettings() {
+			return this.settings;
+		}
+
 		@Override
 		public Optional<Edge> getEdge(String edgeId) {
 			return this.edges.stream().filter(e -> e.getId() == edgeId).findFirst();
@@ -103,7 +108,7 @@ public List<AlertingSetting> getUserAlertingSettings(String edgeId) {
 	}
 
 	public static class EventAdminImpl implements EventAdmin {
-		public List<Event> lastEvents = new ArrayList<>();
+		private List<Event> lastEvents = new ArrayList<>();
 
 		public EventAdminImpl() {
 

io.openems.backend.alerting/test/io/openems/backend/alerting/handler/TestOfflineEdgeHandler.java

@@ -98,7 +98,7 @@ public void checkmetadata() {
 		final var msgsch = new Dummy.MessageSchedulerServiceImpl();
 		final var handler = new OfflineEdgeHandler(msgsch, null, this.metadata, 0);
 
-		final var expected = (int) this.metadata.settings.values().stream().filter(e -> e.stream()
+		final var expected = (int) this.metadata.getSettings().values().stream().filter(e -> e.stream()
 				.filter(s -> s.getDelayTime() > 0).filter(s -> s.getLastNotification().isBefore(this.now)).count() != 0)
 				.count();
 		assertEquals(expected, msgsch.find(handler).size());

io.openems.backend.alerting/test/io/openems/backend/alerting/scheduler/SchedulerTest.java

@@ -117,8 +117,8 @@ private void testHandle() {
 	}
 
 	/* *********************************************** */
-	static class DummyMessage extends Message {
-		ZonedDateTime timeStamp;
+	private static class DummyMessage extends Message {
+		private ZonedDateTime timeStamp;
 
 		public DummyMessage(String messageId, int timeShift) {
 			super(messageId);
@@ -140,9 +140,7 @@ public JsonObject getParams() {
 		}
 	}
 
-	static class DummyHandler implements Handler<DummyMessage> {
-		ZonedDateTime wasSentAt = null;
-
+	private static class DummyHandler implements Handler<DummyMessage> {
 		@Override
 		public Runnable getEventHandler(EventReader event) {
 			throw new UnsupportedOperationException();
@@ -155,7 +153,6 @@ public void stop() {
 
 		@Override
 		public void send(ZonedDateTime sentAt, List<DummyMessage> messages) {
-			this.wasSentAt = sentAt;
 		}
 
 		@Override

io.openems.backend.b2brest/src/io/openems/backend/b2brest/B2bRest.java

@@ -0,0 +1,94 @@
+package io.openems.backend.b2brest;
+
+import org.eclipse.jetty.server.Server;
+import org.osgi.service.component.annotations.Activate;
+import org.osgi.service.component.annotations.Component;
+import org.osgi.service.component.annotations.ConfigurationPolicy;
+import org.osgi.service.component.annotations.Deactivate;
+import org.osgi.service.component.annotations.Reference;
+import org.osgi.service.component.annotations.ReferenceCardinality;
+import org.osgi.service.component.annotations.ReferencePolicy;
+import org.osgi.service.metatype.annotations.Designate;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import io.openems.backend.common.component.AbstractOpenemsBackendComponent;
+import io.openems.backend.common.jsonrpc.JsonRpcRequestHandler;
+import io.openems.backend.common.metadata.Metadata;
+import io.openems.common.exceptions.OpenemsException;
+
+@Designate(ocd = Config.class, factory = true)
+@Component(//
+		name = "Backend2Backend.Rest", //
+		immediate = true, //
+		configurationPolicy = ConfigurationPolicy.REQUIRE //
+)
+public class Backend2BackendRest extends AbstractOpenemsBackendComponent {
+
+	public static final int DEFAULT_PORT = 8075;
+
+	private final Logger log = LoggerFactory.getLogger(Backend2BackendRest.class);
+
+	@Reference(cardinality = ReferenceCardinality.MANDATORY, policy = ReferencePolicy.DYNAMIC)
+	protected volatile JsonRpcRequestHandler jsonRpcRequestHandler;
+
+	@Reference(cardinality = ReferenceCardinality.MANDATORY, policy = ReferencePolicy.DYNAMIC)
+	protected volatile Metadata metadata;
+
+	private Server server = null;
+
+	public Backend2BackendRest() {
+		super("Backend2Backend.Rest");
+	}
+
+	@Activate
+	private void activate(Config config) throws OpenemsException {
+		this.startServer(config.port());
+	}
+
+	@Deactivate
+	private void deactivate() {
+		this.stopServer();
+	}
+
+	/**
+	 * Create and start new server.
+	 *
+	 * @param port the port
+	 * @throws OpenemsException on error
+	 */
+	private synchronized void startServer(int port) throws OpenemsException {
+		try {
+			this.server = new Server(port);
+			this.server.setHandler(new RestHandler(this));
+			this.server.start();
+			this.logInfo(this.log, "Backend2Backend.Rest started on port [" + port + "].");
+		} catch (Exception e) {
+			throw new OpenemsException("Backend2Backend.Rest failed on port [" + port + "].", e);
+		}
+	}
+
+	/**
+	 * Stop existing server.
+	 */
+	private synchronized void stopServer() {
+		if (this.server != null) {
+			try {
+				this.server.stop();
+			} catch (Exception e) {
+				this.logWarn(this.log, "Backend2Backend.Rest failed to stop: " + e.getMessage());
+			}
+		}
+	}
+
+	@Override
+	protected void logInfo(Logger log, String message) {
+		super.logInfo(log, message);
+	}
+
+	@Override
+	protected void logWarn(Logger log, String message) {
+		super.logWarn(log, message);
+	}
+
+}

io.openems.backend.b2brest/src/io/openems/backend/b2brest/Backend2BackendRest.java

@@ -9,7 +9,7 @@
 @interface Config {
 
 	@AttributeDefinition(name = "Port", description = "The port of the REST server.")
-	int port() default B2bRest.DEFAULT_PORT;
+	int port() default Backend2BackendRest.DEFAULT_PORT;
 
 	String webconsole_configurationFactory_nameHint() default "Backend2Backend Rest";
 

io.openems.backend.b2brest/src/io/openems/backend/b2brest/Config.java

@@ -37,9 +37,9 @@ public class RestHandler extends AbstractHandler {
 
 	private final Logger log = LoggerFactory.getLogger(RestHandler.class);
 
-	private final B2bRest parent;
+	private final Backend2BackendRest parent;
 
-	public RestHandler(B2bRest parent) {
+	public RestHandler(Backend2BackendRest parent) {
 		this.parent = parent;
 	}