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

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

@@ -35,6 +35,7 @@
 import com.google.cloud.grpc.GrpcTransportOptions;
 import com.google.cloud.http.HttpTransportOptions;
 import com.google.common.base.MoreObjects;
+import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableSet;
 import java.io.IOException;
 import java.lang.reflect.Method;
@@ -129,7 +130,10 @@ public static class Builder extends ServiceOptions.Builder<Datastore, DatastoreO
     private String databaseId;
     private TransportChannelProvider channelProvider = null;
     private String host;
-    private TransportOptions transportOptions;
+
+    @Nonnull
+    private TransportOptions transportOptions =
+        new DatastoreDefaults().getDefaultTransportOptions();
 
     @Nullable private DatastoreOpenTelemetryOptions openTelemetryOptions = null;
 
@@ -141,13 +145,35 @@ private Builder(DatastoreOptions options) {
       this.databaseId = options.databaseId;
       this.openTelemetryOptions = options.openTelemetryOptions;
       this.channelProvider = validateChannelProvider(options.channelProvider);
+      this.host = options.getHost();
+      this.transportOptions = options.getTransportOptions();
+    }
+
+    private TransportChannelProvider validateChannelProvider(
+        TransportChannelProvider channelProvider) {
+      Preconditions.checkNotNull(channelProvider, "TransportChannelProvider cannot be null");
+      if (!(channelProvider instanceof InstantiatingGrpcChannelProvider)) {
+        throw new IllegalArgumentException(
+            "Only GRPC channels are allowed for " + API_SHORT_NAME + ".");
+      }
+      return channelProvider;
     }
 
+    /**
+     * Sets the transport options.
+     *
+     * @param transportOptions the transport options to set, must be {@link HttpTransportOptions} or
+     *     {@link GrpcTransportOptions}
+     * @return the builder
+     * @throws IllegalArgumentException if the transport options are not supported
+     */
     @Override
-    public Builder setTransportOptions(TransportOptions transportOptions) {
-      if (!(transportOptions instanceof HttpTransportOptions)) {
+    public Builder setTransportOptions(@Nonnull TransportOptions transportOptions) {
+      Preconditions.checkNotNull(transportOptions, "TransportOptions cannot be null");
+      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);
@@ -185,10 +211,28 @@ public Builder setChannelProvider(TransportChannelProvider channelProvider) {
       return this;
     }
 
+    /**
+     * Builds the {@link DatastoreOptions} instance.
+     *
+     * <p>If the host is not explicitly set, it defaults to the transport-specific default host:
+     *
+     * <ul>
+     *   <li>gRPC: {@code datastore.googleapis.com:443}
+     *   <li>HTTP: {@code https://datastore.googleapis.com}
+     * </ul>
+     *
+     * @return the {@link DatastoreOptions} instance
+     */
     @Override
     public DatastoreOptions build() {
-      if (this.host == null && this.transportOptions instanceof GrpcTransportOptions) {
-        this.setHost(DatastoreSettings.getDefaultEndpoint());
+      if (this.host == null) {
+        // Use whatever host value the user passes in, otherwise use the transport specific default
+        // host values
+        if (this.transportOptions instanceof GrpcTransportOptions) {
+          this.setHost(DatastoreSettings.getDefaultEndpoint());
+        } else if (this.transportOptions instanceof HttpTransportOptions) {
+          this.setHost(com.google.datastore.v1.client.DatastoreFactory.DEFAULT_HOST);
+        }
       }
       return new DatastoreOptions(this);
     }
@@ -218,15 +262,6 @@ public Builder setOpenTelemetryOptions(
     }
   }
 
-  private static TransportChannelProvider validateChannelProvider(
-      TransportChannelProvider channelProvider) {
-    if (channelProvider != null && !(channelProvider instanceof InstantiatingGrpcChannelProvider)) {
-      throw new IllegalArgumentException(
-          "Only GRPC channels are allowed for " + API_SHORT_NAME + ".");
-    }
-    return channelProvider;
-  }
-
   private DatastoreOptions(Builder builder) {
     super(DatastoreFactory.class, DatastoreRpcFactory.class, builder, new DatastoreDefaults());
 
@@ -310,8 +345,8 @@ 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())