Azure – java.lang.NoClassDefFoundError: reactor/util/context/ContextView

java.lang.NoClassDefFoundError: reactor/util/context/ContextView

This could be because of missing dependency in your application. Check if you have added the required dependencies to your project’s classpath.

I have reproduced your requirement to upload/download file using Azure Java SDK.

Below are the dependencies which I have used in my application.

dependencies {
implementation 'org.springframework.boot:spring-boot-starter-web'
implementation group: 'com.azure', name: 'azure-storage-blob', version: '12.16.0'
implementation group: 'com.microsoft.azure', name: 'azure-storage-spring-boot-starter', version: '2.2.5'
implementation group: 'commons-fileupload', name: 'commons-fileupload', version: '1.4'
developmentOnly 'org.springframework.boot:spring-boot-devtools'
testImplementation 'org.springframework.boot:spring-boot-starter-test'
}

Note the Access token of your storage account in the Azure portal:

I have created the simple API to call this method which is creating the file and downloading the file from Azure Blob Storage.

@PostMapping("/upload")
public  void  uploadFile(@RequestParam(value  =  "file")  MultipartFile  file)  throws  IOException  {

// Code To Create and File In Blob Storage
String  str = "DefaultEndpointsProtocol=https;AccountName=<storage_account_name>;AccountKey=storage_account_access_key;EndpointSuffix=core.windows.net";
OffsetDateTime  expiryTime  =  OffsetDateTime.now().plusDays(1);
BlobSasPermission  permission  =  new  BlobSasPermission().setReadPermission(true);
BlobServiceSasSignatureValues  values  =  new  BlobServiceSasSignatureValues(expiryTime,  permission).setStartTime(OffsetDateTime.now());
BlobContainerClient  container  =  new  BlobContainerClientBuilder().connectionString(str).containerName("<conatiner_name>").buildClient();
BlobClient  blob  =  container.getBlobClient(file.getOriginalFilename());
blob.upload(file.getInputStream(),  file.getSize(),  true);
String  sasToken  =  blob.generateSas(values);
// Code To Create and File In Blob Storage

// Code To download the File From Blob Storage
URL  url  =  new  URL(blob.getBlobUrl()  +  "?"  +  sasToken);
HttpURLConnection  httpConn  =  (HttpURLConnection)  url.openConnection();
int  responseCode  =  httpConn.getResponseCode();
// Check if the response code is HTTP_OK (200)
if  (responseCode  ==  HttpURLConnection.HTTP_OK)  {
// Open input stream from the HTTP connection
InputStream  inputStream  =  httpConn.getInputStream();
// Open output stream to save the file
FileOutputStream  outputStream  =  new FileOutputStream("C:\Users\win10\Downloads\data.txt");
// Read bytes from input stream and write to output stream
int  bytesRead;
byte[]  buffer  =  new  byte[4096];
while  ((bytesRead  =  inputStream.read(buffer))  !=  -1)  {
outputStream.write(buffer,  0,  bytesRead);
}
// Close streams
outputStream.close();
inputStream.close();
System.out.println("File downloaded");
}  else  {
System.out.println("Failed to download file: "  +  httpConn.getResponseMessage());
}
httpConn.disconnect();
// Code To download the File From Blob Storage
}

Calling the API which I have created and it is generating the url to download the file which has been uploaded as shown below:

Uploaded the file to Azure Blob Storage using the above code:

By using the above code, downloaded the file as data.txt.