Protect against available port actually being unavailable

Closes gh-19355

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/tomcat/TomcatServletWebServerFactoryTests.java

@@ -288,7 +288,7 @@ public class TomcatServletWebServerFactoryTests extends AbstractServletWebServer
 	}
 
 	@Test
-	public void primaryConnectorPortClashThrowsWebServerException() throws IOException {
+	public void primaryConnectorPortClashThrowsWebServerException() throws Exception {
 		doWithBlockedPort((port) -> {
 			TomcatServletWebServerFactory factory = getFactory();
 			factory.setPort(port);
@@ -300,7 +300,7 @@ public class TomcatServletWebServerFactoryTests extends AbstractServletWebServer
 	}
 
 	@Test
-	public void startupFailureDoesNotResultInUnstoppedThreadsBeingReported() throws IOException {
+	public void startupFailureDoesNotResultInUnstoppedThreadsBeingReported() throws Exception {
 		super.portClashOfPrimaryConnectorResultsInPortInUseException();
 		String string = this.outputCapture.toString();
 		assertThat(string).doesNotContain("appears to have started a thread named [main]");

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/reactive/server/AbstractReactiveWebServerFactoryTests.java

@@ -23,6 +23,7 @@ import java.nio.charset.StandardCharsets;
 import java.security.KeyStore;
 import java.time.Duration;
 import java.util.Arrays;
+import java.util.concurrent.Callable;
 
 import javax.net.ssl.KeyManagerFactory;
 import javax.net.ssl.SSLException;
@@ -92,12 +93,15 @@ public abstract class AbstractReactiveWebServerFactoryTests {
 	protected abstract AbstractReactiveWebServerFactory getFactory();
 
 	@Test
-	public void specificPort() {
+	public void specificPort() throws Exception {
 		AbstractReactiveWebServerFactory factory = getFactory();
-		int specificPort = SocketUtils.findAvailableTcpPort(41000);
-		factory.setPort(specificPort);
-		this.webServer = factory.getWebServer(new EchoHandler());
-		this.webServer.start();
+		int specificPort = doWithRetry(() -> {
+			int port = SocketUtils.findAvailableTcpPort(41000);
+			factory.setPort(port);
+			this.webServer = factory.getWebServer(new EchoHandler());
+			this.webServer.start();
+			return port;
+		});
 		Mono<String> result = getWebClient().build().post().uri("/test").contentType(MediaType.TEXT_PLAIN)
 				.body(BodyInserters.fromObject("Hello World")).exchange()
 				.flatMap((response) -> response.bodyToMono(String.class));
@@ -113,6 +117,7 @@ public abstract class AbstractReactiveWebServerFactoryTests {
 	@Test
 	public void basicSslFromFileSystem() {
 		testBasicSslWithKeyStore("src/test/resources/test.jks", "password");
+
 	}
 
 	protected final void testBasicSslWithKeyStore(String keyStore, String keyPassword) {
@@ -335,6 +340,19 @@ public abstract class AbstractReactiveWebServerFactoryTests {
 		assertThat(body).isEqualTo("https");
 	}
 
+	private <T> T doWithRetry(Callable<T> action) throws Exception {
+		Exception lastFailure = null;
+		for (int i = 0; i < 10; i++) {
+			try {
+				return action.call();
+			}
+			catch (Exception ex) {
+				lastFailure = ex;
+			}
+		}
+		throw new IllegalStateException("Action was not successful in 10 attempts", lastFailure);
+	}
+
 	protected static class EchoHandler implements HttpHandler {
 
 		public EchoHandler() {

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/servlet/server/AbstractServletWebServerFactoryTests.java

@@ -44,6 +44,7 @@ import java.util.EnumSet;
 import java.util.HashMap;
 import java.util.Locale;
 import java.util.Map;
+import java.util.concurrent.Callable;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.zip.GZIPInputStream;
@@ -248,10 +249,13 @@ public abstract class AbstractServletWebServerFactoryTests {
 	@Test
 	public void specificPort() throws Exception {
 		AbstractServletWebServerFactory factory = getFactory();
-		int specificPort = SocketUtils.findAvailableTcpPort(41000);
-		factory.setPort(specificPort);
-		this.webServer = factory.getWebServer(exampleServletRegistration());
-		this.webServer.start();
+		int specificPort = doWithRetry(() -> {
+			int port = SocketUtils.findAvailableTcpPort(41000);
+			factory.setPort(port);
+			this.webServer = factory.getWebServer(exampleServletRegistration());
+			this.webServer.start();
+			return port;
+		});
 		assertThat(getResponse("http://localhost:" + specificPort + "/hello")).isEqualTo("Hello World");
 		assertThat(this.webServer.getPort()).isEqualTo(specificPort);
 	}
@@ -822,7 +826,7 @@ public abstract class AbstractServletWebServerFactoryTests {
 	}
 
 	@Test
-	public void portClashOfPrimaryConnectorResultsInPortInUseException() throws IOException {
+	public void portClashOfPrimaryConnectorResultsInPortInUseException() throws Exception {
 		doWithBlockedPort((port) -> {
 			assertThatExceptionOfType(RuntimeException.class).isThrownBy(() -> {
 				AbstractServletWebServerFactory factory = getFactory();
@@ -834,7 +838,7 @@ public abstract class AbstractServletWebServerFactoryTests {
 	}
 
 	@Test
-	public void portClashOfSecondaryConnectorResultsInPortInUseException() throws IOException {
+	public void portClashOfSecondaryConnectorResultsInPortInUseException() throws Exception {
 		doWithBlockedPort((port) -> {
 			assertThatExceptionOfType(RuntimeException.class).isThrownBy(() -> {
 				AbstractServletWebServerFactory factory = getFactory();
@@ -1128,19 +1132,28 @@ public abstract class AbstractServletWebServerFactoryTests {
 		return bean;
 	}
 
-	protected final void doWithBlockedPort(BlockedPortAction action) throws IOException {
-		int port = SocketUtils.findAvailableTcpPort(40000);
-		ServerSocket serverSocket = new ServerSocket();
+	private <T> T doWithRetry(Callable<T> action) throws Exception {
+		Exception lastFailure = null;
 		for (int i = 0; i < 10; i++) {
 			try {
-				serverSocket.bind(new InetSocketAddress(port));
-				break;
+				return action.call();
 			}
 			catch (Exception ex) {
+				lastFailure = ex;
 			}
 		}
+		throw new IllegalStateException("Action was not successful in 10 attempts", lastFailure);
+	}
+
+	protected final void doWithBlockedPort(BlockedPortAction action) throws Exception {
+		ServerSocket serverSocket = new ServerSocket();
+		int blockedPort = doWithRetry(() -> {
+			int port = SocketUtils.findAvailableTcpPort(40000);
+			serverSocket.bind(new InetSocketAddress(port));
+			return port;
+		});
 		try {
-			action.run(port);
+			action.run(blockedPort);
 		}
 		finally {
 			serverSocket.close();