extend AutoClosable and add reset method

src/main/java/com/dumbster/smtp/SimpleSmtpServer.java

@@ -35,30 +35,46 @@
 
 /** Dummy SMTP server for testing purposes. */
 @Slf4j
-public final class SimpleSmtpServer {
-
-	/** When stopping wait this long for any still ongoing transmission */
-	private static final int STOP_TIMEOUT = 20000;
+public final class SimpleSmtpServer implements AutoCloseable {
 
 	/** Default SMTP port is 25. */
 	public static final int DEFAULT_SMTP_PORT = 25;
 
 	/** pick any free port. */
 	public static final int AUTO_SMTP_PORT = 0;
 
+	/** When stopping wait this long for any still ongoing transmission */
+	private static final int STOP_TIMEOUT = 20000;
+
+	private static final Pattern CRLF = Pattern.compile("\r\n");
+
 	/** Stores all of the email received since this instance started up. */
 	private final List<SmtpMessage> receivedMail;
 
-	/** Indicates the server thread that it should stop */
-	private volatile boolean stopped = false;
-
 	/** The server socket this server listens to. */
 	private final ServerSocket serverSocket;
+
 	/** Thread that does the work. */
 	private final Thread workerThread;
 
-	private static final Pattern CRLF = Pattern.compile("\r\n");
+	/** Indicates the server thread that it should stop */
+	private volatile boolean stopped = false;
 
+	/**
+	 * Creates an instance of a started SimpleSmtpServer.
+	 *
+	 * @param port port number the server should listen to
+	 * @return a reference to the running SMTP server
+	 */
+	public static SimpleSmtpServer start(int port) throws IOException {
+		return new SimpleSmtpServer(new ServerSocket(Math.max(port, 0)));
+	}
+
+	/**
+	 * private constructor because factory method {@link #start(int)} better indicates that
+	 * the created server is already running
+	 * @param serverSocket socket to listen on
+	 */
 	private SimpleSmtpServer(ServerSocket serverSocket) {
 		this.receivedMail = new ArrayList<>();
 		this.serverSocket = serverSocket;
@@ -72,6 +88,62 @@ public void run() {
 		this.workerThread.start();
 	}
 
+	/**
+	 * @return the port the server is listening on
+	 */
+	public int getPort() {
+		return serverSocket.getLocalPort();
+	}
+
+	/**
+	 * @return list of {@link SmtpMessage}s received by since start up or last reset.
+	 */
+	public List<SmtpMessage> getReceivedEmails() {
+		synchronized (receivedMail) {
+			return Collections.unmodifiableList(new ArrayList<>(receivedMail));
+		}
+	}
+
+	/**
+	 * forgets all received emails
+	 */
+	public void reset() {
+		synchronized (receivedMail) {
+			receivedMail.clear();
+		}
+	}
+
+	/**
+	 * Stops the server. Server is shutdown after processing of the current request is complete.
+	 */
+	public void stop() {
+		if (stopped) {
+			return;
+		}
+		// Mark us closed
+		stopped = true;
+		try {
+			// Kick the server accept loop
+			serverSocket.close();
+		} catch (IOException e) {
+			log.warn("trouble closing the server socket", e);
+		}
+		// and block until worker is finished
+		try {
+			workerThread.join(STOP_TIMEOUT);
+		} catch (InterruptedException e) {
+			log.warn("interrupted when waiting for worker thread to finish", e);
+		}
+	}
+
+	/**
+	 * synonym for {@link #stop()}
+	 */
+	@Override
+	public void close() {
+		stop();
+	}
+
 	/**
 	 * Main loop of the SMTP server.
 	 */
@@ -107,29 +179,6 @@ private void performWork() {
 		}
 	}
 
-	/**
-	 * Stops the server. Server is shutdown after processing of the current request is complete.
-	 */
-	public void stop() {
-		if (stopped) {
-			return;
-		}
-		// Mark us closed
-		stopped = true;
-		try {
-			// Kick the server accept loop
-			serverSocket.close();
-		} catch (IOException e) {
-			log.warn("trouble closing the server socket", e);
-		}
-		// and block until worker is finished
-		try {
-			workerThread.join(STOP_TIMEOUT);
-		} catch (InterruptedException e) {
-			log.warn("interrupted when waiting for worker thread to finish", e);
-		}
-	}
-
 	/**
 	 * Handle an SMTP transaction, i.e. all activity between initial connect and QUIT command.
 	 *
@@ -197,29 +246,4 @@ private static void sendResponse(PrintWriter out, SmtpResponse smtpResponse) {
 			out.flush();
 		}
 	}
-
-	/**
-	 * Get email received by this instance since start up.
-	 *
-	 * @return List of String
-	 */
-	public List<SmtpMessage> getReceivedEmails() {
-		synchronized (receivedMail) {
-			return Collections.unmodifiableList(new ArrayList<>(receivedMail));
-		}
-	}
-
-	/**
-	 * Creates an instance of SimpleSmtpServer and starts it.
-	 *
-	 * @param port port number the server should listen to
-	 * @return a reference to the running SMTP server
-	 */
-	public static SimpleSmtpServer start(int port) throws IOException {
-		return new SimpleSmtpServer(new ServerSocket(port));
-	}
-
-	public int getPort() {
-		return serverSocket.getLocalPort();
-	}
 }

src/test/java/com/dumbster/smtp/SimpleSmtpServerTest.java

@@ -38,6 +38,7 @@
 import static org.junit.Assert.assertTrue;
 
 public class SimpleSmtpServerTest {
+
 	private SimpleSmtpServer server;
 
 	@Before
@@ -67,6 +68,18 @@ public void testSend() throws MessagingException {
 		assertThat(email.getHeaderValue("To"), is("[email protected]"));
 	}
 
+	@Test
+	public void testSendAndReset() throws MessagingException {
+		sendMessage(server.getPort(), "[email protected]", "Test", "Test Body", "[email protected]");
+		assertThat(server.getReceivedEmails(), hasSize(1));
+
+		server.reset();
+		assertThat(server.getReceivedEmails(), hasSize(0));
+
+		sendMessage(server.getPort(), "[email protected]", "Test", "Test Body", "[email protected]");
+		assertThat(server.getReceivedEmails(), hasSize(1));
+	}
+
 	@Test
 	public void testSendMessageWithCR() throws MessagingException {
 		String bodyWithCR = "\n\nKeep these pesky carriage returns\n\n";

version.txt

@@ -6,6 +6,8 @@ Use Generics and unmodifiable collections to improve usability.
 Reduce visibility of everything that's not public API.
 Add option to auto-pick server port and get picked port from running server.
 Update all kinds of dependencies. (junit4 and hamcrest for testing, slf4j for logging, lombok for coding)
+Extend AutoClosable to enable use in try-with-resource.
+Add reset method to allow using one server in multiple tests.
 
 1.6 (2005-04-04)
 Fixed threading and synchronization problems (sourceforge tracker id: 1111796). Thanks to Charles Hudak for pointing