updated BatchEntry to be an @AutoValue class

gax/src/main/java/com/google/api/gax/batching/BatchEntry.java

@@ -32,37 +32,40 @@
 import com.google.api.core.BetaApi;
 import com.google.api.core.InternalExtensionOnly;
 import com.google.api.core.SettableApiFuture;
-import java.util.List;
+import com.google.auto.value.AutoValue;
+import javax.annotation.Nullable;
 
 /**
  * This class contains the element and it's corresponding unresolved future, which would be resolved
- * when batch is {@link BatchingDescriptor#splitResponse(Object, List) successful} or {@link
- * BatchingDescriptor#splitException(Throwable, List) failed}.
+ * when batch is {@link BatchingDescriptor#splitResponse successful} or {@link
+ * BatchingDescriptor#splitException failed}.
  *
  * @param <ElementT> The type of each individual element to be batched.
  * @param <ElementResultT> The type of the result for each individual element.
  */
 @BetaApi("The surface for batching is not stable yet and may change in the future.")
 @InternalExtensionOnly("For google-cloud-java client use only.")
-public class BatchEntry<ElementT, ElementResultT> {
-  private final ElementT element;
-  private final SettableApiFuture<ElementResultT> resultFuture;
+@AutoValue
+public abstract class BatchEntry<ElementT, ElementResultT> {
 
-  private BatchEntry(ElementT element, SettableApiFuture<ElementResultT> resultFuture) {
-    this.element = element;
-    this.resultFuture = resultFuture;
+  /** Get a new builder. */
+  public static <ElementT, ElementResultT> Builder<ElementT, ElementResultT> newBuilder() {
+    return new AutoValue_BatchEntry.Builder<>();
   }
 
-  public ElementT getElement() {
-    return element;
-  }
+  @Nullable
+  public abstract ElementT getElement();
 
-  public SettableApiFuture<ElementResultT> getResultFuture() {
-    return resultFuture;
-  }
+  public abstract SettableApiFuture<ElementResultT> getResultFuture();
+
+  @AutoValue.Builder
+  public abstract static class Builder<ElementT, ElementResultT> {
+
+    public abstract Builder<ElementT, ElementResultT> setElement(ElementT element);
+
+    public abstract Builder<ElementT, ElementResultT> setResultFuture(
+        SettableApiFuture<ElementResultT> future);
 
-  static <ElementT, ElementResultT> BatchEntry<ElementT, ElementResultT> create(
-      ElementT element, SettableApiFuture<ElementResultT> future) {
-    return new BatchEntry<>(element, future);
+    public abstract BatchEntry<ElementT, ElementResultT> build();
   }
 }

gax/src/main/java/com/google/api/gax/batching/BatcherImpl.java

@@ -55,6 +55,7 @@
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.logging.Level;
 import java.util.logging.Logger;
+
 /**
  * Queues up the elements until {@link #flush()} is called; once batching is over, returned future
  * resolves.
@@ -225,7 +226,7 @@ public void close() throws InterruptedException {
    */
   private static class Batch<ElementT, ElementResultT, RequestT, ResponseT> {
     private final BatchingRequestBuilder<ElementT, RequestT> builder;
-    private final List<BatchEntry<ElementT, ElementResultT>> results;
+    private final List<BatchEntry<ElementT, ElementResultT>> entries;
     private final BatchingDescriptor<ElementT, ElementResultT, RequestT, ResponseT> descriptor;
     private final BatcherStats batcherStats;
     private final long elementThreshold;
@@ -241,7 +242,7 @@ private Batch(
         BatcherStats batcherStats) {
       this.descriptor = descriptor;
       this.builder = descriptor.newRequestBuilder(prototype);
-      this.results = new ArrayList<>();
+      this.entries = new ArrayList<>();
       Long elementCountThreshold = batchingSettings.getElementCountThreshold();
       this.elementThreshold = elementCountThreshold == null ? 0 : elementCountThreshold;
       Long requestByteThreshold = batchingSettings.getRequestByteThreshold();
@@ -251,26 +252,30 @@ private Batch(
 
     void add(ElementT element, SettableApiFuture<ElementResultT> result) {
       builder.add(element);
-      results.add(BatchEntry.create(element, result));
+      entries.add(
+          BatchEntry.<ElementT, ElementResultT>newBuilder()
+              .setElement(element)
+              .setResultFuture(result)
+              .build());
       elementCounter++;
       byteCounter += descriptor.countBytes(element);
     }
 
     void onBatchSuccess(ResponseT response) {
       try {
-        descriptor.splitResponse(response, results);
-        batcherStats.recordBatchElementsCompletion(results);
+        descriptor.splitResponse(response, entries);
+        batcherStats.recordBatchElementsCompletion(entries);
       } catch (Exception ex) {
         onBatchFailure(ex);
       }
     }
 
     void onBatchFailure(Throwable throwable) {
       try {
-        descriptor.splitException(throwable, results);
+        descriptor.splitException(throwable, entries);
       } catch (Exception ex) {
-        for (BatchEntry<ElementT, ElementResultT> result : results) {
-          result.getResultFuture().setException(ex);
+        for (BatchEntry<ElementT, ElementResultT> batchEntry : entries) {
+          batchEntry.getResultFuture().setException(ex);
         }
       }
       batcherStats.recordBatchFailure(throwable);

gax/src/test/java/com/google/api/gax/batching/BatcherStatsTest.java

@@ -74,14 +74,22 @@ public void testEntryFailureOnly() {
     SettableApiFuture<Integer> batchOneResult = SettableApiFuture.create();
     batchOneResult.setException(new IllegalStateException("local element failure"));
     batcherStats.recordBatchElementsCompletion(
-        ImmutableList.of(BatchEntry.create(1, batchOneResult)));
+        ImmutableList.of(
+            BatchEntry.<Integer, Integer>newBuilder()
+                .setElement(1)
+                .setResultFuture(batchOneResult)
+                .build()));
 
     SettableApiFuture<Integer> batchTwoResult = SettableApiFuture.create();
     batchTwoResult.setException(
         ApiExceptionFactory.createException(
             new RuntimeException(), FakeStatusCode.of(StatusCode.Code.UNAVAILABLE), false));
     batcherStats.recordBatchElementsCompletion(
-        ImmutableList.of(BatchEntry.create(2, batchTwoResult)));
+        ImmutableList.of(
+            BatchEntry.<Integer, Integer>newBuilder()
+                .setElement(2)
+                .setResultFuture(batchTwoResult)
+                .build()));
 
     BatchingException ex = batcherStats.asException();
     assertThat(ex)
@@ -102,7 +110,12 @@ public void testRequestAndEntryFailures() {
         ApiExceptionFactory.createException(
             new RuntimeException(), FakeStatusCode.of(StatusCode.Code.ALREADY_EXISTS), false));
 
-    batcherStats.recordBatchElementsCompletion(ImmutableList.of(BatchEntry.create(1, future)));
+    batcherStats.recordBatchElementsCompletion(
+        ImmutableList.of(
+            BatchEntry.<Integer, Integer>newBuilder()
+                .setElement(1)
+                .setResultFuture(future)
+                .build()));
 
     BatchingException ex = batcherStats.asException();
     assertThat(ex)