HTTP-GET header Content-Type is not set, cause server check error

[jjqq2013]

Thanks swagger api!
I found JavaClientCodegen has a problem.
When i define consumers in yaml, it means send request with the specified Content-Type, but unfortunately, HTTP GET does not works, POST and others works.

Sample yaml:

# Example YAML to get you started quickly.
# Be aware that YAML has indentation based scoping.
# Code completion support is available so start typing for available options.
swagger: '2.0'

# This is your document metadata
info:
  version: "0.0.0"
  title: <enter your title>

produces:
  - application/mycom-v1+json
consumes:
  - application/mycom-v1+json

# Describe your paths here
paths:
  # This is a path endpoint. Change it.
  /persons:
    # This is a HTTP operation
    get:
      # Describe this verb here. Note: you can use markdown
      description: |
        Gets `Person` objects.
        Optional query param of **size** determines
        size of returned array
      # This is array of GET operation parameters:
      parameters:
        # An example parameter that is in query and is required
        -
          name: size
          in: query
          description: Size of array
          required: true
          type: number
          format: double
      # Expected responses for this operation:
      responses:
        # Response code
        200:
          description: Successful response
          # A schema describing your response object.
          # Use JSON Schema format
          schema:
            title: ArrayOfPersons
            type: array
            items:
              title: Person
              type: object
              properties:
                name:
                  type: string
                single:
                  type: boolean

Result ClientAPI.java

private ClientResponse getAPIResponse(String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames) throws ApiException {
    if (body != null && !formParams.isEmpty()) {
      throw new ApiException(500, "Cannot have body and form params");
    }

    updateParamsForAuth(authNames, queryParams, headerParams);

    final String url = buildUrl(path, queryParams);
    Builder builder;
    if (accept == null) {
      builder = httpClient.resource(url).getRequestBuilder();
    } else {
      builder = httpClient.resource(url).accept(accept);
    }

    for (String key : headerParams.keySet()) {
      builder = builder.header(key, headerParams.get(key));
    }
    for (String key : defaultHeaderMap.keySet()) {
      if (!headerParams.containsKey(key)) {
        builder = builder.header(key, defaultHeaderMap.get(key));
      }
    }

    ClientResponse response = null;

    if ("GET".equals(method)) {
      response = (ClientResponse) builder.get(ClientResponse.class);   //**** did not use contentType
    } else if ("POST".equals(method)) {
      response = builder.type(contentType).post(ClientResponse.class, serialize(body, contentType, formParams));
    } else if ("PUT".equals(method)) {
      response = builder.type(contentType).put(ClientResponse.class, serialize(body, contentType, formParams));
    } else if ("DELETE".equals(method)) {
      response = builder.type(contentType).delete(ClientResponse.class, serialize(body, contentType, formParams));
    } else {
      throw new ApiException(500, "unknown method type " + method);
    }
    return response;
  }

As you can see above code, contentType is not used for HTTP GET.

When it goes to a spring framework server, the problem occours:

So, the server did right thing, but client did wrong. I need client send Content-Type for HTTP GET.

Would you confirm this problem?

[jjqq2013]

I added three lines to auto-generated ApiClient.java, then it works

Old code begins:

  private ClientResponse getAPIResponse(String path, String method, List<Pair> queryParams, Object body, Map<String, String> headerParams, Map<String, Object> formParams, String accept, String contentType, String[] authNames) throws ApiException {
    if (body != null && !formParams.isEmpty()) {
      throw new ApiException(500, "Cannot have body and form params");
    }

    updateParamsForAuth(authNames, queryParams, headerParams);

    final String url = buildUrl(path, queryParams);
    Builder builder;
    if (accept == null) {
      builder = httpClient.resource(url).getRequestBuilder();
    } else {
      builder = httpClient.resource(url).accept(accept);
    }

Insert following code:

    if ("GET".equals(method) && contentType != null && contentType.length() > 0) {
      headerParams.put("Content-Type", contentType);
    }

Continue old code:

    for (String key : headerParams.keySet()) {
      builder = builder.header(key, headerParams.get(key));
    }
    for (String key : defaultHeaderMap.keySet()) {
      if (!headerParams.containsKey(key)) {
        builder = builder.header(key, defaultHeaderMap.get(key));
      }
    }

    ClientResponse response = null;

    if ("GET".equals(method)) {
      response = (ClientResponse) builder.get(ClientResponse.class);
    } else if ("POST".equals(method)) {
      response = builder.type(contentType).post(ClientResponse.class, serialize(body, contentType, formParams));
    } else if ("PUT".equals(method)) {
      response = builder.type(contentType).put(ClientResponse.class, serialize(body, contentType, formParams));
    } else if ("DELETE".equals(method)) {
      response = builder.type(contentType).delete(ClientResponse.class, serialize(body, contentType, formParams));
    } else {
      throw new ApiException(500, "unknown method type " + method);
    }
    return response;
  }

[fehguy]

But Content-Type is not required with GET requests. Only POST, etc. where you're sending a body.

[jjqq2013]

dear sir, I agree with you, but once define consumes property, the spring framework check request content-type, even HTTP GET. I can not accuse spring guys, because HTTP specification not strictly say no Content-Type for HTTP-GET, just SHOULD.

In other words, Anyone can legally send HTTP-GET with Content-Type and empty body or form! I hav did the experiment use ajax or nodejs. There were many same question about Content-Type and HTTP-GET coexistence in stackoverflow.

To resolve this problem, the only way: add Content-Type to HTTP-GET in client code

[jjqq2013]

The problem is : once user define "consumes" type in yaml, swagger's auto-generated java server and java client will not works.

Other type such as nodejs ApiClient.js, it did set Content-Type in HTTP-GET request.

Would you please consider this problem again?

[wing328]

Have you tested Java API client using other HTTP library (not the default Jersey1.x)?

You can do so by passing -Dlibrary=jersey2 to the command line. For a full list of HTTP libraries supported, please refer to the help page.

[jjqq2013]

i have not tested jersey2, but i have chekced jersey2's ApiClient.java, same problem there. My project do not want to specify extra option to use jersey2.
I will make a test case to prove the problem.

[wing328]

Do you mind testing other Java HTTP libraries to see if there are similar issue? If yes, we want to fix those as well
Supported HTTP libraries in Java: retrofit, retroit2, okhttp-gson, feign, jersey2

[jjqq2013]

Ok, i will try others.

2016年2月27日土曜日、wing328notifications@github.comさんは書きました:

Do you mind testing other Java HTTP libraries to see if there are similar
issue? If yes, we want to fix those as well
Supported HTTP libraries in Java: retrofit, retroit2, okhttp-gson, feign,
jersey2

—
Reply to this email directly or view it on GitHub
#2254 (comment)
.

[ePaul]

Sending a Content-Type where there is no body (other than in a response to HEAD) sounds wrong.

RFC 7231, Section Content-Type:

The "Content-Type" header field indicates the media type of the
associated representation: either the representation enclosed in the
message payload or the selected representation, as determined by the
message semantics.

(This "selected representation" is for responses to HEAD requests.)

I think the top-level consumes property should certainly not apply to GET (or HEAD) requests.
And if Spring-MVC requires a Content-Type for a GET request, then either there is some bug or you configured it wrong.

(And maybe there is a bug in the Swagger-generator for Spring-MVC.)

[jjqq2013]

@ePaul I understand.
YAML does not allow me to define "consumes" (Request's Content-Type) in POST.

swagger: '2.0'
info:
  version: "0.0.0"
  title: <enter your title>

produces:
  - application/mycom-v1+json

paths:
  /persons:
    post:
      #i want to web server check following request's content-type. But syntax error!
      consumes:
        -application/mycom-v1+json
      description: |
        Gets `Person` objects.
      parameters:
        -
          name: size
      responses:
        200:
          description: Successful response
          schema:
            title: ArrayOfPersons
            type: array
            items:
              title: Person
              type: object
              properties:
                name:
                  type: string

So i have to define "consumes" globally, for any HTTP type.
It in turn cause web server's check cause error.

As you can see in above screenshot in first post,
it is spring frame work (NOT swagger's framework) that check request's Content-Type even if no HTTP body, such as when HTTP GET.

So, we have three choice:

1. Modify spring framework's check logic: ignore content-type check if no body.

2. Modify swagger's auto-generated client logic to add Content-Type to request unconditionally.

3. Modify swagger's auto-generated server to tell spring not use "consumes" when HTTP GET.

4. Modify swagger's YAML spec to let "consumes" property apply to down level.

How do you think?