OptimisticConcurrencyManagement.java

// Optimistic
void optimistic(BlobClient blobClient) {
    try {
        // 1st
        String blobContents1 = "First update. Overwrite blob if it exists.";
        byte[] byteArray = blobContents1.getBytes(StandardCharsets.UTF_8);
        InputStream targetStream = new ByteArrayInputStream(byteArray);

        BlobParallelUploadOptions blobParallelUploadOptions = new BlobParallelUploadOptions(targetStream, byteArray.length);
        Response<BlockBlobItem> blobItemResponse = blobClient.uploadWithResponse(blobParallelUploadOptions, null, Context.NONE);
        System.out.println("Content: " + blobContents1);
        System.out.println("Status: " + blobItemResponse.getStatusCode());
        System.out.println("ETag: " + blobItemResponse.getValue().getETag());
        String originalEtag = blobItemResponse.getValue().getETag();

        // 2nd
        String blobContents2 = "Second update overwrites first update.";
        byteArray = blobContents2.getBytes(StandardCharsets.UTF_8);
        targetStream = new ByteArrayInputStream(byteArray);

        blobParallelUploadOptions = new BlobParallelUploadOptions(targetStream, byteArray.length);
        blobItemResponse = blobClient.uploadWithResponse(blobParallelUploadOptions, null, Context.NONE);
        System.out.println("Content: " + blobContents2);
        System.out.println("Status: " + blobItemResponse.getStatusCode());
        System.out.println("ETag: " + blobItemResponse.getValue().getETag());

        // 3rd ETagが一致する場合に上書き（書き換わっているから失敗する）
        String blobContents3 = "Third update. If-Match condition set to original ETag.";
        byteArray = blobContents3.getBytes(StandardCharsets.UTF_8);
        targetStream = new ByteArrayInputStream(byteArray);

        BlobRequestConditions blobRequestConditions = new BlobRequestConditions().setIfMatch(originalEtag);
        blobParallelUploadOptions = new BlobParallelUploadOptions(targetStream, byteArray.length)
                .setRequestConditions(blobRequestConditions);
        blobItemResponse = blobClient.uploadWithResponse(blobParallelUploadOptions, null, Context.NONE);
        System.out.println("Content: " + blobContents3);
        System.out.println("Status: " + blobItemResponse.getStatusCode());
        System.out.println("ETag: " + blobItemResponse.getValue().getETag());
    }
    catch(BlobStorageException e) {
        if(e.getStatusCode() == HttpURLConnection.HTTP_PRECON_FAILED) {
            System.out.println("Precondition failure as expected. Blob's ETag does not match ETag provided.");
        }
        else {
            e.printStackTrace();
        }
    }
}