Polish Undertow access logs contribution

 - Apply project’s code formatting and conventions
 - Don’t use the IO and worker thread configuration when creating the
   worker for the AccessLogReceiver. The IO and worker thread
   configuration is for HTTP request processing and a worker in its
   default configuration should be sufficient for the access log
   receiver.
 - Don’t use a temporary directory as the default for the access log
   directory. A temporary directory makes (some) sense for Tomcat as it
   requires a directory for its basedir. Undertow has no such
   requirement and using a temporary directory makes it hard to locate
   the logs. The default has been updated to a directory named logs,
   created in the current working directory.
 - Document the new properties in the application properties appendix

Closes gh-3014

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/ServerProperties.java

@@ -582,7 +582,7 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer, Ord
 		/**
 		 * Format pattern for access logs.
 		 */
-		private String accessLogPattern;
+		private String accessLogPattern = "common";
 
 		/**
 		 * Enable access log.
@@ -590,9 +590,9 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer, Ord
 		private boolean accessLogEnabled = false;
 
 		/**
-		 * Undertow access log directory. If not specified a temporary directory will be used.
+		 * Undertow access log directory.
 		 */
-		private File accessLogDir;
+		private File accessLogDir = new File("logs");
 
 		public Integer getBufferSize() {
 			return this.bufferSize;
@@ -635,7 +635,7 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer, Ord
 		}
 
 		public String getAccessLogPattern() {
-			return accessLogPattern;
+			return this.accessLogPattern;
 		}
 
 		public void setAccessLogPattern(String accessLogPattern) {
@@ -643,7 +643,7 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer, Ord
 		}
 
 		public boolean isAccessLogEnabled() {
-			return accessLogEnabled;
+			return this.accessLogEnabled;
 		}
 
 		public void setAccessLogEnabled(boolean accessLogEnabled) {
@@ -651,7 +651,7 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer, Ord
 		}
 
 		public File getAccessLogDir() {
-			return accessLogDir;
+			return this.accessLogDir;
 		}
 
 		public void setAccessLogDir(File accessLogDir) {

spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -95,6 +95,9 @@ content into your application; rather pick only the properties that you need.
 	server.tomcat.max-http-header-size= # maximum size in bytes of the HTTP message header
 	server.tomcat.max-threads = 0 # number of threads in protocol handler
 	server.tomcat.uri-encoding = UTF-8 # character encoding to use for URL decoding
+	server.undertow.access-log-enabled=false # if access logging is enabled
+	server.undertow.access-log-pattern=common # log pattern of the access log
+	server.undertow.access-log-dir=logs # access logs directory
 
 	# SPRING MVC ({sc-spring-boot-autoconfigure}/web/WebMvcProperties.{sc-ext}[WebMvcProperties])
 	spring.mvc.locale= # set fixed locale, e.g. en_UK

spring-boot-samples/spring-boot-sample-undertow/src/test/resources/application.properties → spring-boot-samples/spring-boot-sample-undertow/src/main/resources/application.properties

 server.undertow.access-log-enabled=true
+server.undertow.access-log-dir=target/logs
 server.undertow.access-log-pattern=combined
\ No newline at end of file

spring-boot/src/main/java/org/springframework/boot/context/embedded/AbstractEmbeddedServletContainerFactory.java

@@ -32,7 +32,6 @@ import org.apache.commons.logging.LogFactory;
  *
  * @author Phillip Webb
  * @author Dave Syer
- * @author Marcos Barbero
  */
 public abstract class AbstractEmbeddedServletContainerFactory extends
 		AbstractConfigurableEmbeddedServletContainer implements
@@ -79,25 +78,6 @@ public abstract class AbstractEmbeddedServletContainerFactory extends
 		return file;
 	}
 
-	/**
-	 * Returns the absolute temp dir for given web server.
-	 * @param prefix webserver name
-	 * @return The temp dir for given web server.
-	 */
-	protected File createTempDir(String prefix) {
-		try {
-			File tempFolder = File.createTempFile(prefix + ".", "." + getPort());
-			tempFolder.delete();
-			tempFolder.mkdir();
-			tempFolder.deleteOnExit();
-			return tempFolder;
-		}
-		catch (IOException ex) {
-			throw new EmbeddedServletContainerException(
-					String.format("Unable to create %s tempdir", prefix), ex);
-		}
-	}
-
 	private File getExplodedWarFileDocumentRoot() {
 		File file = getCodeSourceArchive();
 		if (this.logger.isDebugEnabled()) {

spring-boot/src/main/java/org/springframework/boot/context/embedded/tomcat/TomcatEmbeddedServletContainerFactory.java

@@ -79,7 +79,6 @@ import org.springframework.util.StringUtils;
  * @author Brock Mills
  * @author Stephane Nicoll
  * @author Andy Wilkinson
- * @author Marcos Barbero
  * @see #setPort(int)
  * @see #setContextLifecycleListeners(Collection)
  * @see TomcatEmbeddedServletContainer
@@ -388,6 +387,25 @@ public class TomcatEmbeddedServletContainerFactory extends
 		this.resourceLoader = resourceLoader;
 	}
 
+	/**
+	 * Returns the absolute temp dir for given web server.
+	 * @param prefix webserver name
+	 * @return The temp dir for given web server.
+	 */
+	protected File createTempDir(String prefix) {
+		try {
+			File tempFolder = File.createTempFile(prefix + ".", "." + getPort());
+			tempFolder.delete();
+			tempFolder.mkdir();
+			tempFolder.deleteOnExit();
+			return tempFolder;
+		}
+		catch (IOException ex) {
+			throw new EmbeddedServletContainerException(
+					"Unable to create Tomcat tempdir", ex);
+		}
+	}
+
 	/**
 	 * Set the Tomcat base directory. If not specified a temporary directory will be used.
 	 * @param baseDirectory the tomcat base directory

spring-boot/src/main/java/org/springframework/boot/context/embedded/undertow/UndertowEmbeddedServletContainerFactory.java

@@ -22,6 +22,7 @@ import io.undertow.UndertowMessages;
 import io.undertow.server.HandlerWrapper;
 import io.undertow.server.HttpHandler;
 import io.undertow.server.handlers.accesslog.AccessLogHandler;
+import io.undertow.server.handlers.accesslog.AccessLogReceiver;
 import io.undertow.server.handlers.accesslog.DefaultAccessLogReceiver;
 import io.undertow.server.handlers.resource.ClassPathResourceManager;
 import io.undertow.server.handlers.resource.FileResourceManager;
@@ -76,8 +77,8 @@ import org.springframework.util.ResourceUtils;
 import org.xnio.OptionMap;
 import org.xnio.Options;
 import org.xnio.SslClientAuthMode;
-import org.xnio.XnioWorker;
 import org.xnio.Xnio;
+import org.xnio.XnioWorker;
 
 /**
  * {@link EmbeddedServletContainerFactory} that can be used to create
@@ -366,45 +367,38 @@ public class UndertowEmbeddedServletContainerFactory extends
 		deploymentInfo.addInitialHandlerChainWrapper(new HandlerWrapper() {
 			@Override
 			public HttpHandler wrap(HttpHandler handler) {
-				try {
-					String formatString = (accessLogPattern != null) ? accessLogPattern
-							: "common";
-					DefaultAccessLogReceiver accessLogReceiver = new DefaultAccessLogReceiver(
-							createWorker(), getLogsDir(), "access_log");
-					return new AccessLogHandler(handler, accessLogReceiver, formatString,
-							Undertow.class.getClassLoader());
-				}
-				catch (IOException ex) {
-					throw new IllegalStateException(ex);
-				}
+				return createAccessLogHandler(handler);
 			}
 		});
 	}
 
-	private XnioWorker createWorker() throws IOException {
-		Xnio xnio = Xnio.getInstance(Undertow.class.getClassLoader());
-		OptionMap.Builder builder = OptionMap.builder();
-		if(this.ioThreads != null && this.ioThreads > 0) {
-			builder.set(Options.WORKER_IO_THREADS, ioThreads);
+	private AccessLogHandler createAccessLogHandler(HttpHandler handler) {
+		try {
+			createAccessLogDirectoryIfNecessary();
+			AccessLogReceiver accessLogReceiver = new DefaultAccessLogReceiver(
+					createWorker(), this.accessLogDirectory, "access_log");
+			String formatString = (this.accessLogPattern != null) ? this.accessLogPattern
+					: "common";
+			return new AccessLogHandler(handler, accessLogReceiver, formatString,
+					Undertow.class.getClassLoader());
 		}
-		if(this.workerThreads != null && this.workerThreads > 0) {
-			builder.set(Options.WORKER_TASK_CORE_THREADS, workerThreads);
-			builder.set(Options.WORKER_TASK_MAX_THREADS, workerThreads);
+		catch (IOException ex) {
+			throw new IllegalStateException("Failed to create AccessLogHandler", ex);
 		}
-		return xnio.createWorker(builder.getMap());
 	}
 
-	private File getLogsDir() {
-		File logsDir;
-		if (accessLogDirectory != null) {
-			logsDir = accessLogDirectory;
-			if (!logsDir.isDirectory() && !logsDir.mkdirs()) {
-				throw new IllegalStateException("Failed to create logs dir '" + logsDir + "'");
-			}
-		} else {
-			logsDir = createTempDir("undertow");
+	private void createAccessLogDirectoryIfNecessary() {
+		Assert.notNull(this.accessLogDirectory, "accesslogDirectory must not be null");
+		if (!this.accessLogDirectory.isDirectory() && !this.accessLogDirectory.mkdirs()) {
+			throw new IllegalStateException("Failed to create access log directory '"
+					+ this.accessLogDirectory + "'");
 		}
-		return logsDir;
+	}
+
+	private XnioWorker createWorker() throws IOException {
+		Xnio xnio = Xnio.getInstance(Undertow.class.getClassLoader());
+		OptionMap.Builder builder = OptionMap.builder();
+		return xnio.createWorker(builder.getMap());
 	}
 
 	private void registerServletContainerInitializerToDriveServletContextInitializers(
@@ -517,7 +511,7 @@ public class UndertowEmbeddedServletContainerFactory extends
 	}
 
 	public boolean isAccessLogEnabled() {
-		return accessLogEnabled;
+		return this.accessLogEnabled;
 	}
 
 	/**