Add TestSocketUtils to spring-test

Fixes spring-projects#28210

spring-test/src/main/java/org/springframework/test/util/TestSocketUtils.java

@@ -0,0 +1,109 @@
+/*
+ * Copyright 2002-2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.test.util;
+
+import java.net.InetAddress;
+import java.net.ServerSocket;
+import java.util.Random;
+
+import javax.net.ServerSocketFactory;
+
+/**
+ * Simple utility methods for finding available ports on {@code localhost} for
+ * use in integration testing scenarios.
+ *
+ * <p>This is a limited form of {@code SocketUtils} which is deprecated in Spring
+ * Framework 5.3 and removed in Spring Framework 6.0.
+ *
+ * <p>{@code SocketUtils} was introduced in Spring Framework 4.0, primarily to
+ * assist in writing integration tests which start an external server on an
+ * available random port. However, these utilities make no guarantee about the
+ * subsequent availability of a given port and are therefore unreliable (the reason
+ * for deprecation and removal).
+ *
+ * <p>Instead of using {@code TestSocketUtils} to find an available local port for a server,
+ * it is recommended that you rely on a server's ability to start on a random port
+ * that it selects or is assigned by the operating system. To interact with that
+ * server, you should query the server for the port it is currently using.
+ *
+ * @author Sam Brannen
+ * @author Ben Hale
+ * @author Arjen Poutsma
+ * @author Gunnar Hillert
+ * @author Gary Russell
+ * @author Chris Bono
+ * @since 5.3
+ */
+public final class TestSocketUtils {
+
+	/**
+	 * The minimum value for port ranges used when finding an available TCP port.
+	 */
+	private static final int PORT_RANGE_MIN = 1024;
+
+	/**
+	 * The maximum value for port ranges used when finding an available TCP port.
+	 */
+	private static final int PORT_RANGE_MAX = 65535;
+
+	private static final int PORT_RANGE = PORT_RANGE_MAX - PORT_RANGE_MIN;
+
+	private static final int MAX_ATTEMPTS = 1_000;
+
+	private static final Random random = new Random(System.nanoTime());
+
+	private TestSocketUtils() {
+	}
+
+	/**
+	 * Find an available TCP port randomly selected from the range [1024, 65535].
+	 * @return an available TCP port number
+	 * @throws IllegalStateException if no available port could be found within max attempts
+	 */
+	public static int findAvailableTcpPort() {
+		int candidatePort;
+		int searchCounter = 0;
+		do {
+			if (searchCounter > MAX_ATTEMPTS) {
+				throw new IllegalStateException(String.format(
+						"Could not find an available TCP port in the range [%d, %d] after %d attempts",
+						PORT_RANGE_MIN, PORT_RANGE_MAX, MAX_ATTEMPTS));
+			}
+			candidatePort = PORT_RANGE_MIN + random.nextInt(PORT_RANGE + 1);
+			searchCounter++;
+		}
+		while (!isPortAvailable(candidatePort));
+
+		return candidatePort;
+	}
+
+	/**
+	 * Determine if the specified TCP port is currently available on {@code localhost}.
+	 */
+	private static boolean isPortAvailable(int port) {
+		try {
+			ServerSocket serverSocket = ServerSocketFactory.getDefault().createServerSocket(
+					port, 1, InetAddress.getByName("localhost"));
+			serverSocket.close();
+			return true;
+		}
+		catch (Exception ex) {
+			return false;
+		}
+	}
+
+}

spring-test/src/test/java/org/springframework/test/util/TestSocketUtilsTests.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2002-2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.test.util;
+
+import javax.net.ServerSocketFactory;
+
+import org.junit.jupiter.api.Test;
+import org.mockito.MockedStatic;
+import org.mockito.Mockito;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
+
+/**
+ * Unit tests for {@link  TestSocketUtils}.
+ *
+ * @author Sam Brannen
+ * @author Gary Russell
+ * @author Chris Bono
+ */
+class TestSocketUtilsTests {
+
+	@Test
+	void findAvailableTcpPort() {
+		int port = TestSocketUtils.findAvailableTcpPort();
+		assertThat(port >= 1024).as("port [" + port + "] >= " + 1024).isTrue();
+		assertThat(port <= 65535).as("port [" + port + "] <= " + 65535).isTrue();
+	}
+
+	@Test
+	void findAvailableTcpPortWhenNoAvailablePortFoundInMaxAttempts()  {
+		try (MockedStatic<ServerSocketFactory> mockedServerSocketFactory = Mockito.mockStatic(ServerSocketFactory.class)) {
+			mockedServerSocketFactory.when(ServerSocketFactory::getDefault).thenThrow(new RuntimeException("Boom"));
+			assertThatIllegalStateException().isThrownBy(TestSocketUtils::findAvailableTcpPort)
+					.withMessageStartingWith("Could not find an available TCP port")
+					.withMessageEndingWith("after 1000 attempts");
+
+		}
+	}
+
+}

spring-test/src/test/resources/mockito-extensions/org.mockito.plugins.MockMaker

@@ -0,0 +1 @@
+mock-maker-inline