default unsupported exception.

Author: rmehta19

gax-java/gax-grpc/src/test/java/com/google/api/gax/grpc/testing/LocalChannelProvider.java

@@ -60,7 +60,6 @@ public class LocalChannelProvider implements TransportChannelProvider {
 
   private final List<LocalHeaderInterceptor> interceptors;
   private final String address;
-  private boolean useS2A;
 
   private volatile HeaderProvider headerProvider;
 
@@ -109,7 +108,7 @@ public TransportChannelProvider withEndpoint(String endpoint) {
 
   @Override
   public TransportChannelProvider withUseS2A(boolean useS2A) {
-    this.useS2A = useS2A;
+    // Overriden for technical reasons. This method is a no-op for LocalChannelProvider.
     return this;
   }
 

gax-java/gax-httpjson/src/main/java/com/google/api/gax/httpjson/InstantiatingHttpJsonChannelProvider.java

@@ -65,7 +65,6 @@ public final class InstantiatingHttpJsonChannelProvider implements TransportChan
   private final HeaderProvider headerProvider;
   private final HttpJsonInterceptorProvider interceptorProvider;
   private final String endpoint;
-  private final boolean useS2A;
   private final HttpTransport httpTransport;
   private final MtlsProvider mtlsProvider;
 
@@ -74,14 +73,12 @@ private InstantiatingHttpJsonChannelProvider(
       HeaderProvider headerProvider,
       HttpJsonInterceptorProvider interceptorProvider,
       String endpoint,
-      boolean useS2A,
       HttpTransport httpTransport,
       MtlsProvider mtlsProvider) {
     this.executor = executor;
     this.headerProvider = headerProvider;
     this.interceptorProvider = interceptorProvider;
     this.endpoint = endpoint;
-    this.useS2A = useS2A;
     this.httpTransport = httpTransport;
     this.mtlsProvider = mtlsProvider;
   }
@@ -129,7 +126,7 @@ public TransportChannelProvider withEndpoint(String endpoint) {
 
   @Override
   public TransportChannelProvider withUseS2A(boolean useS2A) {
-    return toBuilder().setUseS2A(useS2A).build();
+    return this;
   }
 
   /** @deprecated REST transport channel doesn't support channel pooling */
@@ -239,7 +236,6 @@ public static final class Builder {
     private HeaderProvider headerProvider;
     private HttpJsonInterceptorProvider interceptorProvider;
     private String endpoint;
-    private boolean useS2A;
     private HttpTransport httpTransport;
     private MtlsProvider mtlsProvider = new MtlsProvider();
 
@@ -249,7 +245,6 @@ private Builder(InstantiatingHttpJsonChannelProvider provider) {
       this.executor = provider.executor;
       this.headerProvider = provider.headerProvider;
       this.endpoint = provider.endpoint;
-      this.useS2A = provider.useS2A;
       this.httpTransport = provider.httpTransport;
       this.mtlsProvider = provider.mtlsProvider;
       this.interceptorProvider = provider.interceptorProvider;
@@ -304,12 +299,6 @@ public Builder setEndpoint(String endpoint) {
       return this;
     }
 
-    /** Sets whether to use S2A */
-    public Builder setUseS2A(boolean useS2A) {
-      this.useS2A = useS2A;
-      return this;
-    }
-
     /** Sets the HTTP transport to be used. */
     public Builder setHttpTransport(HttpTransport httpTransport) {
       this.httpTransport = httpTransport;
@@ -328,13 +317,7 @@ Builder setMtlsProvider(MtlsProvider mtlsProvider) {
 
     public InstantiatingHttpJsonChannelProvider build() {
       return new InstantiatingHttpJsonChannelProvider(
-          executor,
-          headerProvider,
-          interceptorProvider,
-          endpoint,
-          useS2A,
-          httpTransport,
-          mtlsProvider);
+          executor, headerProvider, interceptorProvider, endpoint, httpTransport, mtlsProvider);
     }
   }
 }

gax-java/gax/src/main/java/com/google/api/gax/rpc/FixedTransportChannelProvider.java

@@ -42,7 +42,6 @@
 public class FixedTransportChannelProvider implements TransportChannelProvider {
 
   private final TransportChannel transportChannel;
-  private boolean useS2A;
 
   private FixedTransportChannelProvider(TransportChannel transportChannel) {
     this.transportChannel = Preconditions.checkNotNull(transportChannel);
@@ -91,8 +90,8 @@ public TransportChannelProvider withEndpoint(String endpoint) {
   }
 
   @Override
-  public TransportChannelProvider withUseS2A(boolean useS2A) {
-    this.useS2A = useS2A;
+  public TransportChannelProvider withUseS2A(boolean useS2A) throws UnsupportedOperationException {
+    // Overriden for technical reasons. This method is a no-op for FixedTransportChannelProvider.
     return this;
   }
 

gax-java/gax/src/main/java/com/google/api/gax/rpc/TransportChannelProvider.java

@@ -98,7 +98,9 @@ public interface TransportChannelProvider {
   TransportChannelProvider withEndpoint(String endpoint);
 
   /** Sets whether to use S2A when constructing a new {@link TransportChannel}. */
-  TransportChannelProvider withUseS2A(boolean useS2A);
+  default TransportChannelProvider withUseS2A(boolean useS2A) {
+    throw new UnsupportedOperationException("S2A is not supported");
+  }
 
   /**
    * Reports whether this provider allows pool size customization.