HADOOP-16600. StagingTestBase uses methods not available in Mockito 1.8.5 in branch-3.1

Signed-off-by: Steve Loughran <stevel@apache.org>
Signed-off-by: Ayush Saxena <ayushsaxena@apache.org>
Signed-off-by: stack <stack@apache.org>

hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/commit/staging/StagingTestBase.java

@@ -49,6 +49,7 @@ import org.junit.AfterClass;
 import org.junit.Assert;
 import org.junit.Before;
 import org.junit.BeforeClass;
+import org.mockito.invocation.InvocationOnMock;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -514,6 +515,21 @@ public class StagingTestBase {
     }
   }
 
+  /**
+   * InvocationOnMock.getArgumentAt comes and goes with Mockito versions; this
+   * helper method is designed to be resilient to change.
+   * @param invocation invocation to query
+   * @param index argument index
+   * @param clazz class of return type
+   * @param <T> type of return
+   * @return the argument of the invocation, cast to the given type.
+   */
+  @SuppressWarnings("unchecked")
+  private static<T> T getArgumentAt(InvocationOnMock invocation, int index,
+      Class<T> clazz) {
+    return (T)invocation.getArguments()[index];
+  }
+
   /**
    * Instantiate mock client with the results and errors requested.
    * @param results results to accrue
@@ -539,7 +555,7 @@ public class StagingTestBase {
                   "Mock Fail on init " + results.requests.size());
             }
             String uploadId = UUID.randomUUID().toString();
-            InitiateMultipartUploadRequest req = invocation.getArgumentAt(
+            InitiateMultipartUploadRequest req = getArgumentAt(invocation,
                 0, InitiateMultipartUploadRequest.class);
             results.requests.put(uploadId, req);
             results.activeUploads.put(uploadId, req.getKey());
@@ -561,7 +577,7 @@ public class StagingTestBase {
               throw new AmazonClientException(
                   "Mock Fail on upload " + results.parts.size());
             }
-            UploadPartRequest req = invocation.getArgumentAt(
+            UploadPartRequest req = getArgumentAt(invocation,
                 0, UploadPartRequest.class);
             results.parts.add(req);
             String etag = UUID.randomUUID().toString();
@@ -588,7 +604,7 @@ public class StagingTestBase {
               throw new AmazonClientException(
                   "Mock Fail on commit " + results.commits.size());
             }
-            CompleteMultipartUploadRequest req = invocation.getArgumentAt(
+            CompleteMultipartUploadRequest req = getArgumentAt(invocation,
                 0, CompleteMultipartUploadRequest.class);
             results.commits.add(req);
             results.activeUploads.remove(req.getUploadId());
@@ -608,7 +624,7 @@ public class StagingTestBase {
           throw new AmazonClientException(
               "Mock Fail on abort " + results.aborts.size());
         }
-        AbortMultipartUploadRequest req = invocation.getArgumentAt(
+        AbortMultipartUploadRequest req = getArgumentAt(invocation,
             0, AbortMultipartUploadRequest.class);
         String id = req.getUploadId();
         String p = results.activeUploads.remove(id);
@@ -630,7 +646,7 @@ public class StagingTestBase {
     doAnswer(invocation -> {
       LOG.debug("deleteObject for {}", mockClient);
       synchronized (lock) {
-        results.deletes.add(invocation.getArgumentAt(
+        results.deletes.add(getArgumentAt(invocation,
             0, DeleteObjectRequest.class));
         return null;
       }
@@ -643,8 +659,8 @@ public class StagingTestBase {
       LOG.debug("deleteObject for {}", mockClient);
       synchronized (lock) {
         results.deletes.add(new DeleteObjectRequest(
-            invocation.getArgumentAt(0, String.class),
-            invocation.getArgumentAt(1, String.class)
+            getArgumentAt(invocation, 0, String.class),
+            getArgumentAt(invocation, 1, String.class)
         ));
         return null;
       }