feat: add isShutdown in HttpTransport

google-http-client-appengine/src/main/java/com/google/api/client/extensions/appengine/http/UrlFetchTransport.java

@@ -32,13 +32,12 @@
  *
  * <p>URL Fetch is only available on Google App Engine (not on any other Java environment), and is
  * the underlying HTTP transport used for App Engine. Their implementation of {@link
- * HttpURLConnection} is simply an abstraction layer on top of URL Fetch. By implementing a
- * transport that directly uses URL Fetch, we can optimize the behavior slightly, and can
- * potentially take advantage of features in URL Fetch that are not available in {@link
- * HttpURLConnection}. Furthermore, there is currently a serious bug in how HTTP headers are
- * processed in the App Engine implementation of {@link HttpURLConnection}, which we are able to
- * avoid using this implementation. Therefore, this is the recommended transport to use on App
- * Engine.
+ * HttpURLConnection} is simply an abstraction layer on top of URL Fetch. By implementing transport
+ * that directly uses URL Fetch, we can optimize the behavior slightly, and can potentially take
+ * advantage of features in URL Fetch that are not available in {@link HttpURLConnection}.
+ * Furthermore, there is currently a serious bug in how HTTP headers are processed in the App Engine
+ * implementation of {@link HttpURLConnection}, which we are able to avoid using this
+ * implementation. Therefore, this is the recommended transport to use on App Engine.
  *
  * @since 1.10
  * @author Yaniv Inbar

google-http-client/src/main/java/com/google/api/client/http/HttpRequest.java

@@ -1103,7 +1103,7 @@ public HttpResponse execute() throws IOException {
     span.end(OpenCensusUtils.getEndSpanOptions(response == null ? null : response.getStatusCode()));
 
     if (response == null) {
-      // Retries did not help resolve the execute exception, re-throw it.
+      // Retries did not help resolve the executed exception, re-throw it.
       throw executeException;
     }
     // response interceptor

google-http-client/src/main/java/com/google/api/client/http/HttpTransport.java

@@ -21,7 +21,7 @@
 /**
  * Thread-safe abstract HTTP transport.
  *
- * <p>Implementation is thread-safe, and sub-classes must be thread-safe. For maximum efficiency,
+ * <p>Implementation is thread-safe, and subclasses must be thread-safe. For maximum efficiency,
  * applications should use a single globally-shared instance of the HTTP transport.
  *
  * <p>The recommended concrete implementation HTTP transport library to use depends on what
@@ -158,4 +158,13 @@ public boolean isMtls() {
    * @since 1.4
    */
   public void shutdown() throws IOException {}
+
+  /**
+   * Default implementation of whether the http transport is shutdown or not.
+   *
+   * @since 1.4
+   */
+  public boolean isShutdown() {
+    return true;
+  }
 }

google-http-client/src/main/java/com/google/api/client/http/javanet/NetHttpTransport.java

@@ -41,16 +41,16 @@
  * <p>Users should consider modifying the keep alive property on {@link NetHttpTransport} to control
  * whether the socket should be returned to a pool of connected sockets. More information is
  * available <a
- * href='http://docs.oracle.com/javase/7/docs/technotes/guides/net/http-keepalive.html'>here</a>.
+ * href="http://docs.oracle.com/javase/7/docs/technotes/guides/net/http-keepalive.html">here</a>.
  *
  * <p>We honor the default global caching behavior. To change the default behavior use {@link
  * HttpURLConnection#setDefaultUseCaches(boolean)}.
  *
  * <p>Implementation is thread-safe. For maximum efficiency, applications should use a single
  * globally-shared instance of the HTTP transport.
  *
- * @since 1.0
  * @author Yaniv Inbar
+ * @since 1.0
  */
 public final class NetHttpTransport extends HttpTransport {
   private static Proxy defaultProxy() {