Implement TimedDownloaderService.

Fix #665

No functional changes.

src/main/java/ru/mystamps/web/config/ServicesConfig.java

@@ -93,13 +93,21 @@ public CronService getCronService() {
 
 	@Bean
 	public DownloaderService getImageDownloaderService() {
-		return new HttpURLConnectionDownloaderService(new String[]{"image/jpeg", "image/png"});
+		return new TimedDownloaderService(
+			LoggerFactory.getLogger(TimedDownloaderService.class),
+			new HttpURLConnectionDownloaderService(
+				new String[]{"image/jpeg", "image/png"}
+			)
+		);
 	}
 
 	@Bean
 	public DownloaderService getSeriesDownloaderService() {
-		return new HttpURLConnectionDownloaderService(
-			new String[]{"text/html", "image/jpeg", "image/png"}
+		return new TimedDownloaderService(
+			LoggerFactory.getLogger(TimedDownloaderService.class),
+			new HttpURLConnectionDownloaderService(
+				new String[]{"text/html", "image/jpeg", "image/png"}
+			)
 		);
 	}
 

src/main/java/ru/mystamps/web/service/TimedDownloaderService.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2009-2018 Slava Semushin <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+package ru.mystamps.web.service;
+
+import org.apache.commons.lang3.time.StopWatch;
+
+import org.slf4j.Logger;
+
+import lombok.RequiredArgsConstructor;
+
+import ru.mystamps.web.service.dto.DownloadResult;
+
+@RequiredArgsConstructor
+public class TimedDownloaderService implements DownloaderService {
+
+	private final Logger log;
+	private final DownloaderService service;
+
+	// @todo #665 TimedDownloaderService: add unit tests
+	@Override
+	public DownloadResult download(String url) {
+		// Why we don't use Spring's StopWatch?
+		// 1) because its javadoc says that it's not intended for production
+		// 2) because we don't want to have strong dependencies on the Spring Framework
+		StopWatch timer = new StopWatch();
+
+		// start() and stop() may throw IllegalStateException and in this case it's possible
+		// that we won't generate anything or lose already generated result. I don't want to
+		// make method body too complicated by adding many try/catches and I believe that such
+		// exception will never happen because it would mean that we're using API in a wrong way.
+		timer.start();
+		DownloadResult result = service.download(url);
+		timer.stop();
+
+		if (result.hasSucceeded()) {
+			log.debug(
+				"{} bytes have been downloaded in {} msecs",
+				result.getData().length,
+				timer.getTime()
+			);
+		}
+
+		return result;
+	}
+
+}

src/main/java/ru/mystamps/web/service/dto/DownloadResult.java

@@ -45,6 +45,10 @@ public boolean hasFailed() {
 		return code != Code.SUCCESS;
 	}
 
+	public boolean hasSucceeded() {
+		return code == Code.SUCCESS;
+	}
+
 	public String getDataAsString() {
 		return new String(data, StandardCharsets.UTF_8);
 	}