What this request provide (problem with method argument)

[Jan Kaczmarek]

Hello,
I am trying to write a method that will respond to this http request. Unfortunately, I do not know what the argument of such a method should be.

cat data.csv | curl --header "Content-Type: text/plain" --request PUT --data-binary @- http://localhost:8080/endpoint

swagger:

put:
      tags:
      - "employees"
      summary: "Stores employees hierarchy tree on server"
      description: "Sends or replaces employees hierarchy tree on server"
      operationId: "endpoint"
      consumes:
      - "text/plain"
      parameters:
      - in: "body"
        name: "body"
        description: "CSV with four columns - employee id, employee name, employee surname and employee superior id. Columns are separated with ',' character."
        required: true
        schema:
          type: string
          example:[tons of employees data here]

At first I thought it would be a Multipartfile and then I would just process it (see dummy approach below), but then I saw a "string" in swagger and it confused me a bit. I have no clue anymore what the format of the input data is.
(I know- I should use nio, no io)

    @PutMapping("/endpoint")
    public void readCSV(MultipartFile file) throws IOException {
        String content = new String(file.getBytes());
        System.out.println(content);
}

[Tim Holloway]

I'm confused. You appear to be attempting to POST a CSV file named "data.csv". You post a file labelled "swagger", which is a YAML file (not CSV). Probably there's a MIME (Content-Type) more appropriate to use than "text/plain"  for CSV. Like, say, "text/csv". But that's secondary.

Youd server-side code appears to expect MIME-multipart input, but your curl command is set up to simply blast raw data to the server without form variable naming, MIME or multi-partitioning. And that's OK, as long as the server doesn't try and treat it like is is any of those creatures. You want to configure to receive an InputStream, String, or similar character sequence without the extra stuff that an HTTP FORM submit would add.

[Jan Kaczmarek]

This swagger is just representing my API endpoint documentation (this is the PUT part of it).
CSV example (the one I made for tests)

5,Yesterday,All,root
3,My,Troubles,2
4,Seemed,So,5
0,Far,Away,2
7,Now,it,2
6,Looks,as,3
8,though,they're,5
1,here,to,8
9,stay,oh,4

I cannot edit the request. I have to conform to it. The whole problem is with this part:

   @PutMapping("/endpoint")
    public void readCSV( > WHAT ARGUMENT SHOULD BE HERE < )  {
}

[Rob Spoor]

Multipart is a bad choice for CSVs. It's meant to send multiple values like a regular form post, but with files as well. MultipartFile is used for one element of a multipart request. You're not sending a multipart request so that's not going to work.

Your specifation says that the content type is "text/plain", and the type of the body parameter is "string". That means that you should just use String as body type, and parse the content yourself. A better option would be to use "text/csv", but I'm not sure how this can be easily mapped to objects.

[Tim Holloway]

Yeah, I agree with Rob - I'm just out of practice so I wasn't going to make foolish suggestions.

As far as MIME type text/csv, I don't think it's going to make any difference functionally, but it's good practice.

[Jan Kaczmarek]

So the method accepting such a request will look like this :

@PutMapping("/endpoint")
    public void readCSV(@RequestBody String csvData) 

because this request actually accepts a CSV file, but passes all its contents to me on the server side in the form of a String, am I right?
After this PUT I will have argument, that looks like:

String csvData = "5,Yesterday,All,root
3,My,Troubles,2
4,Seemed,So,5
0,Far,Away,2
7,Now,it,2
6,Looks,as,3
8,though,they're,5
1,here,to,8
9,stay,oh,4"

[Tim Holloway]

Looks good to me.

[Rob Spoor]

You can use a library like opencsv or Apache Commons CSV to parse the contents. I think you can even use Jackson with jackson-dataformat-csv to parse it directly to objects.

Whatever you do, don't parse the contents yourself. CSV may look simple, but you may get unexpected results if the CSV becomes a bit more advanced (like including quotes around string values).

[Jan Kaczmarek]

Rob Spoor wrote:You can use a library like opencsv or Apache Commons CSV to parse the contents. I think you can even use Jackson with jackson-dataformat-csv to parse it directly to objects.

Whatever you do, don't parse the contents yourself. CSV may look simple, but you may get unexpected results if the CSV becomes a bit more advanced (like including quotes around string values).

The problem is that these libraries work on CSV files - I get it in the form of one String on the server side, so I probably have to choose the form

    public String[] stringToArray(String csvData) {
        String[] lines = csvData.split("\n");
        return lines;
    }

[Tim Holloway]

Actually, Apache OpenCSV for one allows parsing CSV strings. I didn't check the others, but it's to be expected.

Plus, pretty much any textfile parser can parse strings by using a String Reader.

[Rob Spoor]

Tim Holloway wrote:Plus, pretty much any textfile parser can parse strings by using a String Reader.

That statement is so important I'm quoting it. Every String can be turned into a Reader by using StringReader. Every byte[] can be turned into an InputStream by using ByteArrayInputStream. That allows you to use String and byte[] with code that can handle any type of text or binary input.

Besides that, Jackson's ObjectMapper has readValue methods that take a String. Combined with the data format I linked to you can have Jackson convert the CSV string into POJOs for you.