Load DockerClientProviderStrategy via ServiceLoader (#434) (#435)

Author: srempfer

core/src/main/java/org/testcontainers/DockerClientFactory.java

@@ -25,13 +25,13 @@
 import java.io.InputStream;
 import java.net.Socket;
 import java.nio.charset.Charset;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
+import java.util.ServiceLoader;
 import java.util.function.BiFunction;
 import java.util.function.Consumer;
 
-import static java.util.Arrays.asList;
-
 /**
  * Singleton class that provides initialized Docker clients.
  * <p>
@@ -46,13 +46,6 @@ public class DockerClientFactory {
     // Cached client configuration
     private DockerClientProviderStrategy strategy;
     private boolean preconditionsChecked = false;
-
-    private static final List<DockerClientProviderStrategy> CONFIGURATION_STRATEGIES =
-            asList(new EnvironmentAndSystemPropertyClientProviderStrategy(),
-                    new UnixSocketClientProviderStrategy(),
-                    new ProxiedUnixSocketClientProviderStrategy(),
-                    new DockerMachineClientProviderStrategy(),
-                    new WindowsClientProviderStrategy());
     private String activeApiVersion;
     private String activeExecutionDriver;
 
@@ -91,7 +84,10 @@ public DockerClient client() {
             return strategy.getClient();
         }
 
-        strategy = DockerClientProviderStrategy.getFirstValidStrategy(CONFIGURATION_STRATEGIES);
+        List<DockerClientProviderStrategy> configurationStrategies = new ArrayList<DockerClientProviderStrategy>();
+        ServiceLoader.load(DockerClientProviderStrategy.class).forEach( cs -> configurationStrategies.add( cs ) );
+
+        strategy = DockerClientProviderStrategy.getFirstValidStrategy(configurationStrategies);
 
         String hostIpAddress = strategy.getDockerHostIpAddress();
         log.info("Docker host IP address is {}", hostIpAddress);

core/src/main/java/org/testcontainers/dockerclient/DockerClientProviderStrategy.java

@@ -170,16 +170,4 @@ protected void ping(DockerClient client, int timeoutInSeconds) {
     public String getDockerHostIpAddress() {
         return DockerClientConfigUtils.getDockerHostIpAddress(this.config);
     }
-
-
-    class InvalidConfigurationException extends RuntimeException {
-
-        public InvalidConfigurationException(String s) {
-            super(s);
-        }
-
-        public InvalidConfigurationException(String message, Throwable cause) {
-            super(message, cause);
-        }
-    }
 }

core/src/main/java/org/testcontainers/dockerclient/InvalidConfigurationException.java

@@ -0,0 +1,15 @@
+package org.testcontainers.dockerclient;
+
+/**
+ * Exception to indicate that a {@link DockerClientProviderStrategy} fails.
+ */
+public class InvalidConfigurationException extends RuntimeException {
+
+    public InvalidConfigurationException(String s) {
+        super(s);
+    }
+
+    public InvalidConfigurationException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}

core/src/main/resources/META-INF/services/org.testcontainers.dockerclient.DockerClientProviderStrategy

@@ -0,0 +1,5 @@
+org.testcontainers.dockerclient.EnvironmentAndSystemPropertyClientProviderStrategy
+org.testcontainers.dockerclient.UnixSocketClientProviderStrategy
+org.testcontainers.dockerclient.ProxiedUnixSocketClientProviderStrategy
+org.testcontainers.dockerclient.DockerMachineClientProviderStrategy
+org.testcontainers.dockerclient.WindowsClientProviderStrategy