我正在尝试使用Java SDK v2从S3 Bucket下载文件。我能够成功上传和列出存储桶中的对象，但是当我尝试下载以前上传的对象时，我得到下面列出的错误堆栈跟踪。我已经通过UI检查了存储桶内容，并且对象都已就位，也不是空对象。请指教。
这是获取对象的代码片段：
GetObjectRequest getRequest = GetObjectRequest.builder()
.bucket(bucketName)
.key(objKey)
.build();
s3.getObject(getRequest,
ResponseTransformer.toFile(Paths.get(fileName)));
这是错误堆栈跟踪：
software.amazon.awssdk.core.exception.SdkClientException: Unable to unmarshall response (null). Response Code: 200, Response Text: OK
at software.amazon.awssdk.core.exception.SdkClientException$BuilderImpl.build(SdkClientException.java:97)
at software.amazon.awssdk.core.internal.http.pipeline.stages.HandleResponseStage.handleSuccessResponse(HandleResponseStage.java:100)
at software.amazon.awssdk.core.internal.http.pipeline.stages.HandleResponseStage.handleResponse(HandleResponseStage.java:70)
at software.amazon.awssdk.core.internal.http.pipeline.stages.HandleResponseStage.execute(HandleResponseStage.java:58)
at software.amazon.awssdk.core.internal.http.pipeline.stages.HandleResponseStage.execute(HandleResponseStage.java:41)
at software.amazon.awssdk.core.internal.http.pipeline.RequestPipelineBuilder$ComposingRequestPipelineStage.execute(RequestPipelineBuilder.java:206)
at software.amazon.awssdk.core.internal.http.pipeline.stages.ApiCallAttemptTimeoutTrackingStage.execute(ApiCallAttemptTimeoutTrackingStage.java:64)
at software.amazon.awssdk.core.internal.http.pipeline.stages.ApiCallAttemptTimeoutTrackingStage.execute(ApiCallAttemptTimeoutTrackingStage.java:36)
at software.amazon.awssdk.core.internal.http.pipeline.stages.TimeoutExceptionHandlingStage.execute(TimeoutExceptionHandlingStage.java:77)
at software.amazon.awssdk.core.internal.http.pipeline.stages.TimeoutExceptionHandlingStage.execute(TimeoutExceptionHandlingStage.java:39)
at software.amazon.awssdk.core.internal.http.pipeline.stages.RetryableStage$RetryExecutor.doExecute(RetryableStage.java:113)
at software.amazon.awssdk.core.internal.http.pipeline.stages.RetryableStage$RetryExecutor.execute(RetryableStage.java:86)
at software.amazon.awssdk.core.internal.http.pipeline.stages.RetryableStage.execute(RetryableStage.java:62)
at software.amazon.awssdk.core.internal.http.pipeline.stages.RetryableStage.execute(RetryableStage.java:42)
at software.amazon.awssdk.core.internal.http.pipeline.RequestPipelineBuilder$ComposingRequestPipelineStage.execute(RequestPipelineBuilder.java:206)
at software.amazon.awssdk.core.internal.http.StreamManagingStage.execute(StreamManagingStage.java:57)
at software.amazon.awssdk.core.internal.http.StreamManagingStage.execute(StreamManagingStage.java:37)
at software.amazon.awssdk.core.internal.http.pipeline.stages.ApiCallTimeoutTrackingStage.executeWithTimer(ApiCallTimeoutTrackingStage.java:80)
at software.amazon.awssdk.core.internal.http.pipeline.stages.ApiCallTimeoutTrackingStage.execute(ApiCallTimeoutTrackingStage.java:60)
at software.amazon.awssdk.core.internal.http.pipeline.stages.ApiCallTimeoutTrackingStage.execute(ApiCallTimeoutTrackingStage.java:42)
at software.amazon.awssdk.core.internal.http.pipeline.RequestPipelineBuilder$ComposingRequestPipelineStage.execute(RequestPipelineBuilder.java:206)
at software.amazon.awssdk.core.internal.http.pipeline.RequestPipelineBuilder$ComposingRequestPipelineStage.execute(RequestPipelineBuilder.java:206)
at software.amazon.awssdk.core.internal.http.pipeline.stages.ExecutionFailureExceptionReportingStage.execute(ExecutionFailureExceptionReportingStage.java:37)
at software.amazon.awssdk.core.internal.http.pipeline.stages.ExecutionFailureExceptionReportingStage.execute(ExecutionFailureExceptionReportingStage.java:26)
at software.amazon.awssdk.core.internal.http.AmazonSyncHttpClient$RequestExecutionBuilderImpl.execute(AmazonSyncHttpClient.java:240)
at software.amazon.awssdk.core.client.handler.BaseSyncClientHandler.invoke(BaseSyncClientHandler.java:96)
at software.amazon.awssdk.core.client.handler.BaseSyncClientHandler.execute(BaseSyncClientHandler.java:120)
at software.amazon.awssdk.core.client.handler.BaseSyncClientHandler.execute(BaseSyncClientHandler.java:61)
at software.amazon.awssdk.core.client.handler.SdkSyncClientHandler.execute(SdkSyncClientHandler.java:51)
at software.amazon.awssdk.awscore.client.handler.AwsSyncClientHandler.execute(AwsSyncClientHandler.java:62)
at software.amazon.awssdk.services.s3.DefaultS3Client.getObject(DefaultS3Client.java:1597)
at com.alshaya.phoenix.integration.s3.ObjectOperations.getObject(ObjectOperations.java:43)
at com.alshaya.phoenix.integration.s3.ObjectOperationsTestCase.tc4FileDownload(ObjectOperationsTestCase.java:100)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:89)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:41)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:541)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:763)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:463)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209)
Caused by: software.amazon.awssdk.core.exception.NonRetryableException
at software.amazon.awssdk.core.exception.NonRetryableException$BuilderImpl.build(NonRetryableException.java:91)
at software.amazon.awssdk.core.client.handler.BaseSyncClientHandler$HttpResponseHandlerAdapter.transformResponse(BaseSyncClientHandler.java:161)
at software.amazon.awssdk.core.client.handler.BaseSyncClientHandler$HttpResponseHandlerAdapter.handle(BaseSyncClientHandler.java:142)
at software.amazon.awssdk.core.internal.http.pipeline.stages.HandleResponseStage.handleSuccessResponse(HandleResponseStage.java:89)
... 56 more
Caused by: java.io.IOException: Failed to read response into file: C:\u04\out\test_file_0.bin
at software.amazon.awssdk.core.sync.ResponseTransformer.lambda$toFile$1(ResponseTransformer.java:113)
at software.amazon.awssdk.core.client.handler.BaseSyncClientHandler$HttpResponseHandlerAdapter.transformResponse(BaseSyncClientHandler.java:154)
... 58 more
Caused by: java.nio.file.FileAlreadyExistsException: C:\u04\out\test_file_0.bin
at sun.nio.fs.WindowsException.translateToIOException(Unknown Source)
at sun.nio.fs.WindowsException.rethrowAsIOException(Unknown Source)
at sun.nio.fs.WindowsException.rethrowAsIOException(Unknown Source)
at sun.nio.fs.WindowsFileSystemProvider.newByteChannel(Unknown Source)
at java.nio.file.spi.FileSystemProvider.newOutputStream(Unknown Source)
at java.nio.file.Files.newOutputStream(Unknown Source)
at java.nio.file.Files.copy(Unknown Source)
at software.amazon.awssdk.core.sync.ResponseTransformer.lambda$toFile$1(ResponseTransformer.java:106)
... 59 more
由于您本地驱动器上的文件已存在，因此您的代码会引发异常。如果您的意图是尝试使用不同的文件名或启用覆盖。
Caused by: java.nio.file.FileAlreadyExistsException: C:\u04\out\test_file_0.bin