How to send and download a file as a response to graphql query in java?

@arnoldo.moen 

To send and download a file as a response to a GraphQL query in Java, you can follow these steps:

1. Create a GraphQL schema that includes a query for downloading a file. For example, you can define a query like this:

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type Query {
  downloadFile(fileId: ID!): File
}

1. Create a resolver for the downloadFile query that handles the file download. In the resolver method, you can read the file from the disk or an external storage system, and then return the file object.

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public File downloadFile(String fileId) {
  // Read the file content from the disk or external storage
  File file = new File("path/to/file.txt");
  
  return file;
}

1. In the GraphQL controller or service method where you execute the query, call the resolver method to get the file object:

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ExecutionResult executionResult = graphQL.execute(query);
File file = executionResult.getData().get("downloadFile", File.class);

1. Once you have the file object, you can send it as a response to the client. You can serialize the file object to a byte array or stream and send it over the network.

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// Serialize the file object to a byte array
byte[] fileBytes = serializeFile(file);

// Send the file bytes as a response to the client
response.getOutputStream().write(fileBytes);

1. On the client side, you can download the file by making an HTTP request to the GraphQL API with the appropriate query:

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query {
  downloadFile(fileId: "12345") {
    name
    size
    type
    data
  }
}

By following these steps, you can send and download a file as a response to a GraphQL query in Java.