How to upload files with graphql-java?

I can't find out how to upload files if i use graphql-java, can someone show me a demo? I will be appreciated!

reference : https://github.com/graphql-java-kickstart/graphql-java-tools/issues/240

I tried it in springboot by using graphql-java-kickstart graphql-java-tools, but it didn't work

@Component
public class FilesUpload implements GraphQLMutationResolver {

    public Boolean testMultiFilesUpload(List<Part> parts, DataFetchingEnvironment env) {
        // get file parts from DataFetchingEnvironment, the parts parameter is not used
        List<Part> attchmentParts = env.getArgument("files");
        System.out.println(attchmentParts);
        return true;
    }
}

this is my schema

type Mutation {
    testSingleFileUpload(file: Upload): UploadResult
}

I expect this resolver can print attchmentParts,so i can get the file part.

1. define a scalar type in our schema

   scalar Upload

   and we should configure GraphQLScalarType for Upload, use this below:

   @Configuration
   public class GraphqlConfig {
   
      @Bean
      public GraphQLScalarType uploadScalarDefine() {
         return ApolloScalars.Upload;
      } 
   }
   

2. then we would define a mutation in schema and a GraphQLMutationResolver for testMultiFilesUpload

   type Mutation {
     testMultiFilesUpload(files: [Upload!]!): Boolean
   }
   

here is Resolver:

public Boolean testMultiFilesUpload(List<Part> parts, DataFetchingEnvironment env) {
    // get file parts from DataFetchingEnvironment, the parts parameter is not use
    List<Part> attachmentParts = env.getArgument("files");
    int i = 1;
    for (Part part : attachmentParts) {
      String uploadName = "copy" + i;
      try {
        part.write("your path:" + uploadName);
      } catch (IOException e) {
        e.printStackTrace();
      }
      i++;
    }
    return true;   
  }
}

3. configure a jackson deserializer for javax.servlet.http.Part and register it to ObjectMapper

   public class PartDeserializer extends JsonDeserializer<Part> {
   
     @Override
     public Part deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {         
        return null;
     }
   }
   

   why we return null? because the List<Part> parts always null ,In the resolver's method, get the parts argument from the DataFetchingEnvironment;

   environment.getArgument("files")

register it to ObjectMapper:

@Bean
public ObjectMapper objectMapper() {
  ObjectMapper objectMapper = new ObjectMapper();
  objectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
  SimpleModule module = new SimpleModule();
  module.addDeserializer(Part.class, new PartDeserializer());
  objectMapper.registerModule(module);
  return objectMapper;
}

4. To test this, post the following form data (we use Postman) to GraphQL endpoint

operations

{ "query": "mutation($files: [Upload!]!) {testMultiFilesUpload(files:$files)}", "variables": {"files": [null,null] } }

map

{ "file0": ["variables.files.0"] , "file1":["variables.files.1"]}

file0

your file

file1

your file

like this:

remember to select the form-data option

through this we can upload multiple files