Package com.azure.storage.blob

Class BlobAsyncClient

java.lang.Object
com.azure.storage.blob.specialized.BlobAsyncClientBase
com.azure.storage.blob.BlobAsyncClient
public class BlobAsyncClient extends BlobAsyncClientBase
This class provides a client that contains generic blob operations for Azure Storage Blobs. Operations allowed by the client are uploading and downloading, copying a blob, retrieving and setting metadata, retrieving and setting HTTP headers, and deleting and un-deleting a blob.

This client is instantiated through BlobClientBuilder or retrieved via getBlobAsyncClient.

For operations on a specific blob type (i.e. append, block, or page) use getAppendBlobAsyncClient, getBlockBlobAsyncClient, or getPageBlobAsyncClient to construct a client that allows blob specific operations.

Please refer to the Azure Docs for more information.

  • Field Details

    • BLOB_DEFAULT_UPLOAD_BLOCK_SIZE

      public static final int BLOB_DEFAULT_UPLOAD_BLOCK_SIZE
      The block size to use if none is specified in parallel operations.
      See Also:

    • BLOB_DEFAULT_NUMBER_OF_BUFFERS

      public static final int BLOB_DEFAULT_NUMBER_OF_BUFFERS
      The number of buffers to use if none is specified on the buffered upload method.
      See Also:

    • BLOB_DEFAULT_HTBB_UPLOAD_BLOCK_SIZE

      public static final int BLOB_DEFAULT_HTBB_UPLOAD_BLOCK_SIZE
      If a blob is known to be greater than 100MB, using a larger block size will trigger some server-side optimizations. If the block size is not set and the size of the blob is known to be greater than 100MB, this value will be used.
      See Also:

  • Constructor Details

    • BlobAsyncClient

      protected BlobAsyncClient(com.azure.core.http.HttpPipeline pipeline, String url, BlobServiceVersion serviceVersion, String accountName, String containerName, String blobName, String snapshot, CpkInfo customerProvidedKey)
      Protected constructor for use by BlobClientBuilder.
      Parameters:
      pipeline - The pipeline used to send and receive service requests.
      url - The endpoint where to send service requests.
      serviceVersion - The version of the service to receive requests.
      accountName - The storage account name.
      containerName - The container name.
      blobName - The blob name.
      snapshot - The snapshot identifier for the blob, pass null to interact with the blob directly.
      customerProvidedKey - Customer provided key used during encryption of the blob's data on the server, pass null to allow the service to use its own encryption.

    • BlobAsyncClient

      protected BlobAsyncClient(com.azure.core.http.HttpPipeline pipeline, String url, BlobServiceVersion serviceVersion, String accountName, String containerName, String blobName, String snapshot, CpkInfo customerProvidedKey, com.azure.storage.blob.implementation.models.EncryptionScope encryptionScope)
      Protected constructor for use by BlobClientBuilder.
      Parameters:
      pipeline - The pipeline used to send and receive service requests.
      url - The endpoint where to send service requests.
      serviceVersion - The version of the service to receive requests.
      accountName - The storage account name.
      containerName - The container name.
      blobName - The blob name.
      snapshot - The snapshot identifier for the blob, pass null to interact with the blob directly.
      customerProvidedKey - Customer provided key used during encryption of the blob's data on the server, pass null to allow the service to use its own encryption.
      encryptionScope - Encryption scope used during encryption of the blob's data on the server, pass null to allow the service to use its own encryption.

    • BlobAsyncClient

      protected BlobAsyncClient(com.azure.core.http.HttpPipeline pipeline, String url, BlobServiceVersion serviceVersion, String accountName, String containerName, String blobName, String snapshot, CpkInfo customerProvidedKey, com.azure.storage.blob.implementation.models.EncryptionScope encryptionScope, String versionId)
      Protected constructor for use by BlobClientBuilder.
      Parameters:
      pipeline - The pipeline used to send and receive service requests.
      url - The endpoint where to send service requests.
      serviceVersion - The version of the service to receive requests.
      accountName - The storage account name.
      containerName - The container name.
      blobName - The blob name.
      snapshot - The snapshot identifier for the blob, pass null to interact with the blob directly.
      customerProvidedKey - Customer provided key used during encryption of the blob's data on the server, pass null to allow the service to use its own encryption.
      encryptionScope - Encryption scope used during encryption of the blob's data on the server, pass null to allow the service to use its own encryption.
      versionId - The version identifier for the blob, pass null to interact with the latest blob version.

  • Method Details

    • getSnapshotClient

      public BlobAsyncClient getSnapshotClient(String snapshot)
      Creates a new BlobAsyncClient linked to the snapshot of this blob resource.
      Overrides:
      getSnapshotClient in class BlobAsyncClientBase
      Parameters:
      snapshot - the identifier for a specific snapshot of this blob
      Returns:
      A BlobAsyncClient used to interact with the specific snapshot.

    • getVersionClient

      public BlobAsyncClient getVersionClient(String versionId)
      Creates a new BlobAsyncClient linked to the versionId of this blob resource.
      Overrides:
      getVersionClient in class BlobAsyncClientBase
      Parameters:
      versionId - the identifier for a specific version of this blob, pass null to interact with the latest blob version.
      Returns:
      A BlobAsyncClient used to interact with the specific version.

    • getEncryptionScopeAsyncClient

      public BlobAsyncClient getEncryptionScopeAsyncClient(String encryptionScope)
      Creates a new BlobAsyncClient with the specified encryptionScope.
      Overrides:
      getEncryptionScopeAsyncClient in class BlobAsyncClientBase
      Parameters:
      encryptionScope - the encryption scope for the blob, pass null to use no encryption scope.
      Returns:
      a BlobAsyncClient with the specified encryptionScope.

    • getCustomerProvidedKeyAsyncClient

      public BlobAsyncClient getCustomerProvidedKeyAsyncClient(CustomerProvidedKey customerProvidedKey)
      Creates a new BlobAsyncClient with the specified customerProvidedKey.
      Overrides:
      getCustomerProvidedKeyAsyncClient in class BlobAsyncClientBase
      Parameters:
      customerProvidedKey - the CustomerProvidedKey for the blob, pass null to use no customer provided key.
      Returns:
      a BlobAsyncClient with the specified customerProvidedKey.

    • getAppendBlobAsyncClient

      public AppendBlobAsyncClient getAppendBlobAsyncClient()
      Creates a new AppendBlobAsyncClient associated with this blob.
      Returns:
      A AppendBlobAsyncClient associated with this blob.

    • getBlockBlobAsyncClient

      public BlockBlobAsyncClient getBlockBlobAsyncClient()
      Creates a new BlockBlobAsyncClient associated with this blob.
      Returns:
      A BlockBlobAsyncClient associated with this blob.

    • getPageBlobAsyncClient

      public PageBlobAsyncClient getPageBlobAsyncClient()
      Creates a new PageBlobAsyncClient associated with this blob.
      Returns:
      A PageBlobAsyncClient associated with this blob.

    • upload

      public Mono<BlockBlobItem> upload(Flux<ByteBuffer> data, ParallelTransferOptions parallelTransferOptions)
      Creates a new block blob. By default, this method will not overwrite an existing blob.

      Updating an existing block blob overwrites any existing metadata on the blob. Partial updates are not supported with this method; the content of the existing blob is overwritten with the new content. To perform a partial update of a block blob's, use stageBlock and commitBlockList. For more information, see the Azure Docs for Put Block and the Azure Docs for Put Block List.

      The data passed need not support multiple subscriptions/be replayable as is required in other upload methods when retries are enabled, and the length of the data need not be known in advance. Therefore, this method does support uploading any arbitrary data source, including network streams. This behavior is possible because this method will perform some internal buffering as configured by the blockSize and numBuffers parameters, so while this method may offer additional convenience, it will not be as performant as other options, which should be preferred when possible.

      Typically, the greater the number of buffers used, the greater the possible parallelism when transferring the data. Larger buffers means we will have to stage fewer blocks and therefore require fewer IO operations. The trade-offs between these values are context-dependent, so some experimentation may be required to optimize inputs for a given scenario.

      Code Samples

       ParallelTransferOptions parallelTransferOptions = new ParallelTransferOptions()
     .setBlockSizeLong(blockSize)
     .setMaxConcurrency(maxConcurrency);
 client.upload(data, parallelTransferOptions).subscribe(response ->
     System.out.printf("Uploaded BlockBlob MD5 is %s%n",
         Base64.getEncoder().encodeToString(response.getContentMd5())));
      Parameters:
      data - The data to write to the blob. Unlike other upload methods, this method does not require that the Flux be replayable. In other words, it does not have to support multiple subscribers and is not expected to produce the same values across subscriptions.
      parallelTransferOptions - ParallelTransferOptions used to configure buffered uploading.
      Returns:
      A reactive response containing the information of the uploaded block blob.

    • upload

      public Mono<BlockBlobItem> upload(Flux<ByteBuffer> data, ParallelTransferOptions parallelTransferOptions, boolean overwrite)
      Creates a new block blob, or updates the content of an existing block blob.

      Updating an existing block blob overwrites any existing metadata on the blob. Partial updates are not supported with this method; the content of the existing blob is overwritten with the new content. To perform a partial update of a block blob's, use stageBlock and commitBlockList. For more information, see the Azure Docs for Put Block and the Azure Docs for Put Block List.

      The data passed need not support multiple subscriptions/be replayable as is required in other upload methods when retries are enabled, and the length of the data need not be known in advance. Therefore, this method does support uploading any arbitrary data source, including network streams. This behavior is possible because this method will perform some internal buffering as configured by the blockSize and numBuffers parameters, so while this method may offer additional convenience, it will not be as performant as other options, which should be preferred when possible.

      Typically, the greater the number of buffers used, the greater the possible parallelism when transferring the data. Larger buffers means we will have to stage fewer blocks and therefore require fewer IO operations. The trade-offs between these values are context-dependent, so some experimentation may be required to optimize inputs for a given scenario.

      Code Samples

       ParallelTransferOptions parallelTransferOptions = new ParallelTransferOptions()
     .setBlockSizeLong(blockSize)
     .setMaxConcurrency(maxConcurrency);
 boolean overwrite = false; // Default behavior
 client.upload(data, parallelTransferOptions, overwrite).subscribe(response ->
     System.out.printf("Uploaded BlockBlob MD5 is %s%n",
         Base64.getEncoder().encodeToString(response.getContentMd5())));
      Parameters:
      data - The data to write to the blob. Unlike other upload methods, this method does not require that the Flux be replayable. In other words, it does not have to support multiple subscribers and is not expected to produce the same values across subscriptions.
      parallelTransferOptions - ParallelTransferOptions used to configure buffered uploading.
      overwrite - Whether to overwrite, should the blob already exist.
      Returns:
      A reactive response containing the information of the uploaded block blob.

    • upload

      public Mono<BlockBlobItem> upload(com.azure.core.util.BinaryData data)
      Creates a new block blob. By default, this method will not overwrite an existing blob.

      Code Samples

       client.upload(BinaryData.fromString("Data!")).subscribe(response ->
     System.out.printf("Uploaded BlockBlob MD5 is %s%n",
         Base64.getEncoder().encodeToString(response.getContentMd5())));
      Parameters:
      data - The data to write to the blob.
      Returns:
      A reactive response containing the information of the uploaded block blob.

    • upload

      public Mono<BlockBlobItem> upload(com.azure.core.util.BinaryData data, boolean overwrite)
      Creates a new block blob, or updates the content of an existing block blob.

      Code Samples

       boolean overwrite = false; // Default behavior
 client.upload(BinaryData.fromString("Data!"), overwrite).subscribe(response ->
     System.out.printf("Uploaded BlockBlob MD5 is %s%n",
         Base64.getEncoder().encodeToString(response.getContentMd5())));
      Parameters:
      data - The data to write to the blob.
      overwrite - Whether to overwrite, should the blob already exist.
      Returns:
      A reactive response containing the information of the uploaded block blob.

    • uploadWithResponse

      public Mono<com.azure.core.http.rest.Response<BlockBlobItem>> uploadWithResponse(Flux<ByteBuffer> data, ParallelTransferOptions parallelTransferOptions, BlobHttpHeaders headers, Map<String,String> metadata, AccessTier tier, BlobRequestConditions requestConditions)
      Creates a new block blob, or updates the content of an existing block blob.

      Updating an existing block blob overwrites any existing metadata on the blob. Partial updates are not supported with this method; the content of the existing blob is overwritten with the new content. To perform a partial update of a block blob's, use stageBlock and commitBlockList. For more information, see the Azure Docs for Put Block and the Azure Docs for Put Block List.

      The data passed need not support multiple subscriptions/be replayable as is required in other upload methods when retries are enabled, and the length of the data need not be known in advance. Therefore, this method does support uploading any arbitrary data source, including network streams. This behavior is possible because this method will perform some internal buffering as configured by the blockSize and numBuffers parameters, so while this method may offer additional convenience, it will not be as performant as other options, which should be preferred when possible.

      Typically, the greater the number of buffers used, the greater the possible parallelism when transferring the data. Larger buffers means we will have to stage fewer blocks and therefore require fewer IO operations. The trade-offs between these values are context-dependent, so some experimentation may be required to optimize inputs for a given scenario.

      To avoid overwriting, pass "*" to BlobRequestConditions.setIfNoneMatch(String).

      Code Samples

       BlobHttpHeaders headers = new BlobHttpHeaders()
     .setContentMd5("data".getBytes(StandardCharsets.UTF_8))
     .setContentLanguage("en-US")
     .setContentType("binary");

 Map<String, String> metadata = Collections.singletonMap("metadata", "value");
 BlobRequestConditions requestConditions = new BlobRequestConditions()
     .setLeaseId(leaseId)
     .setIfUnmodifiedSince(OffsetDateTime.now().minusDays(3));

 ParallelTransferOptions parallelTransferOptions = new ParallelTransferOptions()
     .setBlockSizeLong(blockSize)
     .setMaxConcurrency(maxConcurrency);

 client.uploadWithResponse(data, parallelTransferOptions, headers, metadata, AccessTier.HOT, requestConditions)
     .subscribe(response -> System.out.printf("Uploaded BlockBlob MD5 is %s%n",
         Base64.getEncoder().encodeToString(response.getValue().getContentMd5())));

      Using Progress Reporting

       BlobHttpHeaders headers = new BlobHttpHeaders()
     .setContentMd5("data".getBytes(StandardCharsets.UTF_8))
     .setContentLanguage("en-US")
     .setContentType("binary");

 Map<String, String> metadata = Collections.singletonMap("metadata", "value");
 BlobRequestConditions requestConditions = new BlobRequestConditions()
     .setLeaseId(leaseId)
     .setIfUnmodifiedSince(OffsetDateTime.now().minusDays(3));

 ParallelTransferOptions parallelTransferOptions = new ParallelTransferOptions()
     .setBlockSizeLong(blockSize)
     .setMaxConcurrency(maxConcurrency)
     .setProgressListener(bytesTransferred -> System.out.printf("Upload progress: %s bytes sent", bytesTransferred));

 client.uploadWithResponse(data, parallelTransferOptions, headers, metadata, AccessTier.HOT, requestConditions)
     .subscribe(response -> System.out.printf("Uploaded BlockBlob MD5 is %s%n",
         Base64.getEncoder().encodeToString(response.getValue().getContentMd5())));
      Parameters:
      data - The data to write to the blob. Unlike other upload methods, this method does not require that the Flux be replayable. In other words, it does not have to support multiple subscribers and is not expected to produce the same values across subscriptions.
      parallelTransferOptions - ParallelTransferOptions used to configure buffered uploading.
      headers - BlobHttpHeaders
      metadata - Metadata to associate with the blob. If there is leading or trailing whitespace in any metadata key or value, it must be removed or encoded.
      tier - AccessTier for the destination blob.
      requestConditions - BlobRequestConditions
      Returns:
      A reactive response containing the information of the uploaded block blob.

    • uploadWithResponse

      public Mono<com.azure.core.http.rest.Response<BlockBlobItem>> uploadWithResponse(BlobParallelUploadOptions options)
      Creates a new block blob, or updates the content of an existing block blob.

      Updating an existing block blob overwrites any existing metadata on the blob. Partial updates are not supported with this method; the content of the existing blob is overwritten with the new content. To perform a partial update of a block blob's, use stageBlock and commitBlockList. For more information, see the Azure Docs for Put Block and the Azure Docs for Put Block List.

      The data passed need not support multiple subscriptions/be replayable as is required in other upload methods when retries are enabled, and the length of the data need not be known in advance. Therefore, this method does support uploading any arbitrary data source, including network streams. This behavior is possible because this method will perform some internal buffering as configured by the blockSize and numBuffers parameters, so while this method may offer additional convenience, it will not be as performant as other options, which should be preferred when possible.

      Typically, the greater the number of buffers used, the greater the possible parallelism when transferring the data. Larger buffers means we will have to stage fewer blocks and therefore require fewer IO operations. The trade-offs between these values are context-dependent, so some experimentation may be required to optimize inputs for a given scenario.

      To avoid overwriting, pass "*" to BlobRequestConditions.setIfNoneMatch(String).

      Code Samples

       BlobHttpHeaders headers = new BlobHttpHeaders()
     .setContentMd5("data".getBytes(StandardCharsets.UTF_8))
     .setContentLanguage("en-US")
     .setContentType("binary");

 Map<String, String> metadata = Collections.singletonMap("metadata", "value");
 Map<String, String> tags = Collections.singletonMap("tag", "value");
 BlobRequestConditions requestConditions = new BlobRequestConditions()
     .setLeaseId(leaseId)
     .setIfUnmodifiedSince(OffsetDateTime.now().minusDays(3));

 ParallelTransferOptions parallelTransferOptions = new ParallelTransferOptions().setBlockSizeLong(blockSize)
     .setMaxConcurrency(maxConcurrency).setProgressListener(bytesTransferred ->
         System.out.printf("Upload progress: %s bytes sent", bytesTransferred));

 client.uploadWithResponse(new BlobParallelUploadOptions(data)
     .setParallelTransferOptions(parallelTransferOptions).setHeaders(headers).setMetadata(metadata).setTags(tags)
     .setTier(AccessTier.HOT).setRequestConditions(requestConditions))
     .subscribe(response -> System.out.printf("Uploaded BlockBlob MD5 is %s%n",
         Base64.getEncoder().encodeToString(response.getValue().getContentMd5())));

      Using Progress Reporting

       BlobHttpHeaders headers = new BlobHttpHeaders()
     .setContentMd5("data".getBytes(StandardCharsets.UTF_8))
     .setContentLanguage("en-US")
     .setContentType("binary");

 Map<String, String> metadata = Collections.singletonMap("metadata", "value");
 Map<String, String> tags = Collections.singletonMap("tag", "value");
 BlobRequestConditions requestConditions = new BlobRequestConditions()
     .setLeaseId(leaseId)
     .setIfUnmodifiedSince(OffsetDateTime.now().minusDays(3));

 ParallelTransferOptions parallelTransferOptions = new ParallelTransferOptions().setBlockSizeLong(blockSize)
     .setMaxConcurrency(maxConcurrency).setProgressListener(bytesTransferred ->
         System.out.printf("Upload progress: %s bytes sent", bytesTransferred));

 client.uploadWithResponse(new BlobParallelUploadOptions(data)
     .setParallelTransferOptions(parallelTransferOptions).setHeaders(headers).setMetadata(metadata).setTags(tags)
     .setTier(AccessTier.HOT).setRequestConditions(requestConditions))
     .subscribe(response -> System.out.printf("Uploaded BlockBlob MD5 is %s%n",
         Base64.getEncoder().encodeToString(response.getValue().getContentMd5())));
      Parameters:
      options - BlobParallelUploadOptions. Unlike other upload methods, this method does not require that the Flux be replayable. In other words, it does not have to support multiple subscribers and is not expected to produce the same values across subscriptions.
      Returns:
      A reactive response containing the information of the uploaded block blob.

    • uploadFromFile

      public Mono<Void> uploadFromFile(String filePath)
      Creates a new block blob with the content of the specified file. By default, this method will not overwrite an existing blob.

      Code Samples

       client.uploadFromFile(filePath)
     .doOnError(throwable -> System.err.printf("Failed to upload from file %s%n", throwable.getMessage()))
     .subscribe(completion -> System.out.println("Upload from file succeeded"));
      Parameters:
      filePath - Path to the upload file
      Returns:
      An empty response
      Throws:
      UncheckedIOException - If an I/O error occurs

    • uploadFromFile

      public Mono<Void> uploadFromFile(String filePath, boolean overwrite)
      Creates a new block blob, or updates the content of an existing block blob, with the content of the specified file.

      Code Samples

       boolean overwrite = false; // Default behavior
 client.uploadFromFile(filePath, overwrite)
     .doOnError(throwable -> System.err.printf("Failed to upload from file %s%n", throwable.getMessage()))
     .subscribe(completion -> System.out.println("Upload from file succeeded"));
      Parameters:
      filePath - Path to the upload file
      overwrite - Whether to overwrite, should the blob already exist.
      Returns:
      An empty response
      Throws:
      UncheckedIOException - If an I/O error occurs

    • uploadFromFile

      public Mono<Void> uploadFromFile(String filePath, ParallelTransferOptions parallelTransferOptions, BlobHttpHeaders headers, Map<String,String> metadata, AccessTier tier, BlobRequestConditions requestConditions)
      Creates a new block blob, or updates the content of an existing block blob, with the content of the specified file.

      To avoid overwriting, pass "*" to BlobRequestConditions.setIfNoneMatch(String).

      Code Samples

       BlobHttpHeaders headers = new BlobHttpHeaders()
     .setContentMd5("data".getBytes(StandardCharsets.UTF_8))
     .setContentLanguage("en-US")
     .setContentType("binary");

 Map<String, String> metadata = Collections.singletonMap("metadata", "value");
 BlobRequestConditions requestConditions = new BlobRequestConditions()
     .setLeaseId(leaseId)
     .setIfUnmodifiedSince(OffsetDateTime.now().minusDays(3));

 client.uploadFromFile(filePath,
     new ParallelTransferOptions().setBlockSizeLong(BlockBlobClient.MAX_STAGE_BLOCK_BYTES_LONG),
     headers, metadata, AccessTier.HOT, requestConditions)
     .doOnError(throwable -> System.err.printf("Failed to upload from file %s%n", throwable.getMessage()))
     .subscribe(completion -> System.out.println("Upload from file succeeded"));
      Parameters:
      filePath - Path to the upload file
      parallelTransferOptions - ParallelTransferOptions to use to upload from file. Number of parallel transfers parameter is ignored.
      headers - BlobHttpHeaders
      metadata - Metadata to associate with the blob. If there is leading or trailing whitespace in any metadata key or value, it must be removed or encoded.
      tier - AccessTier for the destination blob.
      requestConditions - BlobRequestConditions
      Returns:
      An empty response
      Throws:
      UncheckedIOException - If an I/O error occurs

    • uploadFromFileWithResponse

      public Mono<com.azure.core.http.rest.Response<BlockBlobItem>> uploadFromFileWithResponse(BlobUploadFromFileOptions options)
      Creates a new block blob, or updates the content of an existing block blob, with the content of the specified file.

      To avoid overwriting, pass "*" to BlobRequestConditions.setIfNoneMatch(String).

      Code Samples

       BlobHttpHeaders headers = new BlobHttpHeaders()
     .setContentMd5("data".getBytes(StandardCharsets.UTF_8))
     .setContentLanguage("en-US")
     .setContentType("binary");

 Map<String, String> metadata = Collections.singletonMap("metadata", "value");
 Map<String, String> tags = Collections.singletonMap("tag", "value");
 BlobRequestConditions requestConditions = new BlobRequestConditions()
     .setLeaseId(leaseId)
     .setIfUnmodifiedSince(OffsetDateTime.now().minusDays(3));
 Long blockSize = 100 * 1024 * 1024L; // 100 MB;

 client.uploadFromFileWithResponse(new BlobUploadFromFileOptions(filePath)
     .setParallelTransferOptions(
         new ParallelTransferOptions().setBlockSizeLong(blockSize))
     .setHeaders(headers).setMetadata(metadata).setTags(tags).setTier(AccessTier.HOT)
     .setRequestConditions(requestConditions))
     .doOnError(throwable -> System.err.printf("Failed to upload from file %s%n", throwable.getMessage()))
     .subscribe(completion -> System.out.println("Upload from file succeeded"));
      Parameters:
      options - BlobUploadFromFileOptions
      Returns:
      A reactive response containing the information of the uploaded block blob.
      Throws:
      UncheckedIOException - If an I/O error occurs

    • uploadFileResourceSupplier

      @Deprecated protected AsynchronousFileChannel uploadFileResourceSupplier(String filePath)
      Deprecated.
      due to refactoring code to be in the common storage library.
      RESERVED FOR INTERNAL USE. Resource Supplier for UploadFile.
      Parameters:
      filePath - The path for the file
      Returns:
      AsynchronousFileChannel
      Throws:
      UncheckedIOException - an input output exception.