feat(Datastore): Swap the default transport from HttpJson to gRPC

Author: lqiu96

java-datastore/google-cloud-datastore/src/main/java/com/google/cloud/datastore/DatastoreOptions.java

@@ -131,21 +131,26 @@ public static class Builder extends ServiceOptions.Builder<Datastore, DatastoreO
 
     @Nullable private DatastoreOpenTelemetryOptions openTelemetryOptions = null;
 
-    private Builder() {}
+    private Builder() {
+      this.transportOptions = new DatastoreDefaults().getDefaultTransportOptions();
+    }
 
     private Builder(DatastoreOptions options) {
       super(options);
       this.namespace = options.namespace;
       this.databaseId = options.databaseId;
       this.openTelemetryOptions = options.openTelemetryOptions;
       this.channelProvider = validateChannelProvider(options.channelProvider);
+      this.host = options.getHost();
+      this.transportOptions = options.getTransportOptions();
     }
 
     @Override
     public Builder setTransportOptions(TransportOptions transportOptions) {
-      if (!(transportOptions instanceof HttpTransportOptions)) {
+      if (!(transportOptions instanceof HttpTransportOptions)
+          && !(transportOptions instanceof GrpcTransportOptions)) {
         throw new IllegalArgumentException(
-            "Only http transport is allowed for " + API_SHORT_NAME + ".");
+            "Only http and grpc transport are allowed for " + API_SHORT_NAME + ".");
       }
       this.transportOptions = transportOptions;
       return super.setTransportOptions(transportOptions);
@@ -308,8 +313,8 @@ public TransportOptions getDefaultTransportOptions() {
       return TRANSPORT_OPTIONS;
     }
 
-    public static HttpTransportOptions.Builder getDefaultTransportOptionsBuilder() {
-      return HttpTransportOptions.newBuilder();
+    public static GrpcTransportOptions.Builder getDefaultTransportOptionsBuilder() {
+      return GrpcTransportOptions.newBuilder();
     }
   }
 

java-datastore/google-cloud-datastore/src/test/java/com/google/cloud/datastore/DatastoreOptionsTest.java

@@ -281,8 +281,17 @@ public void testInvalidConfigForHttp() {
 
   @Test
   public void testTransport() {
-    // default http transport
-    assertThat(options.build().getTransportOptions()).isInstanceOf(HttpTransportOptions.class);
+    // default grpc transport
+    assertThat(options.build().getTransportOptions()).isInstanceOf(GrpcTransportOptions.class);
+
+    // custom http transport
+    DatastoreOptions httpTransportOptions =
+        DatastoreOptions.newBuilder()
+            .setTransportOptions(HttpTransportOptions.newBuilder().build())
+            .setProjectId(PROJECT_ID)
+            .setCredentials(NoCredentials.getInstance())
+            .build();
+    assertThat(httpTransportOptions.getTransportOptions()).isInstanceOf(HttpTransportOptions.class);
 
     // custom grpc transport
     DatastoreOptions grpcTransportOptions =
@@ -317,15 +326,24 @@ public void testHostWithGrpcAndHttp() {
             .build();
     assertThat(grpcTransportOptionsCustomHost.getHost()).isEqualTo(customHost);
 
+    DatastoreOptions defaultTransportOptions =
+        DatastoreOptions.newBuilder()
+            .setProjectId(PROJECT_ID)
+            .setCredentials(NoCredentials.getInstance())
+            .build();
+    assertThat(defaultTransportOptions.getHost()).isEqualTo(DatastoreSettings.getDefaultEndpoint());
+
     DatastoreOptions httpTransportOptions =
         DatastoreOptions.newBuilder()
+            .setTransportOptions(HttpTransportOptions.newBuilder().build())
             .setProjectId(PROJECT_ID)
             .setCredentials(NoCredentials.getInstance())
             .build();
     assertThat(httpTransportOptions.getHost()).isEqualTo(DatastoreFactory.DEFAULT_HOST);
 
     DatastoreOptions httpTransportOptionsCustomHost =
         DatastoreOptions.newBuilder()
+            .setTransportOptions(HttpTransportOptions.newBuilder().build())
             .setHost(customHost)
             .setProjectId(PROJECT_ID)
             .setCredentials(NoCredentials.getInstance())