Make ClientTransport extend Closeable

client/client-api/src/main/java/software/amazon/smithy/java/client/core/Client.java

@@ -5,6 +5,9 @@
 
 package software.amazon.smithy.java.client.core;
 
+import java.io.Closeable;
+import java.io.IOException;
+import java.io.UncheckedIOException;
 import java.util.List;
 import java.util.concurrent.CompletionException;
 import java.util.function.Predicate;
@@ -29,7 +32,7 @@
 /**
  * Base Smithy client class.
  */
-public abstract class Client {
+public abstract class Client implements Closeable {
 
     private final ClientConfig config;
     private final ClientPipeline<?, ?> pipeline;
@@ -130,6 +133,18 @@ public ClientConfig config() {
         return config;
     }
 
+    /**
+     * Closes the transport used by this client.
+     */
+    @Override
+    public void close() {
+        try {
+            config.transport().close();
+        } catch (IOException e) {
+            throw new UncheckedIOException(e);
+        }
+    }
+
     /**
      * Builder for Clients and request overrides.
      *

client/client-api/src/main/java/software/amazon/smithy/java/client/core/ClientTransport.java

@@ -5,6 +5,8 @@
 
 package software.amazon.smithy.java.client.core;
 
+import java.io.Closeable;
+import java.io.IOException;
 import java.net.ConnectException;
 import java.net.ProtocolException;
 import java.net.SocketException;
@@ -25,7 +27,7 @@
  * @implNote To be discoverable by dynamic clients and client code generators,
  * ClientTransport's should implement a {@link ClientTransportFactory} service provider.
  */
-public interface ClientTransport<RequestT, ResponseT> {
+public interface ClientTransport<RequestT, ResponseT> extends Closeable {
     /**
      * Send a prepared request.
      *
@@ -46,6 +48,14 @@ public interface ClientTransport<RequestT, ResponseT> {
      */
     MessageExchange<RequestT, ResponseT> messageExchange();
 
+    /**
+     * {@inheritDoc}
+     *
+     * <p>Default implementation is a no-op.
+     */
+    @Override
+    default void close() throws IOException {}
+
     /**
      * Remaps a thrown exception to an appropriate {@link TransportException} or {@link CallException}.
      *

client/client-http/src/main/java/software/amazon/smithy/java/client/http/JavaHttpClientTransport.java

@@ -207,6 +207,11 @@ private static HttpVersion javaToSmithyVersion(HttpClient.Version version) {
         };
     }
 
+    @Override
+    public void close() {
+        client.close();
+    }
+
     public static final class Factory implements ClientTransportFactory<HttpRequest, HttpResponse> {
         @Override
         public String name() {