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TestSocketUtils.java
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/
TestSocketUtils.java
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/*
* 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;
}
}
}