BUG [JAVA] Generated java client code from openapi-generator-maven-plugin using okhttp-gson library failing to serialize RequestBody with contentType text/plain

[prkumarm]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

Generated java client code from openapi-generator-maven-plugin using okhttp-gson library failing to serialize RequestBody with contentType text/plain.

When using httpok library(okhttp-gson) openapi-generator throws ApiException with message "Content type text/plain is not supported" for contentType text/plain.

I see below related mustache template code in serialize(Object obj, String contentType) method in ApiClient.mustache
https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/resources/Java/libraries/okhttp-gson/ApiClient.mustache

Is this a expected behavior? if so, what is the work around to serialize RequestBody of type text/plain

openapi-generator version

5.1.0

OpenApi generator dependency
org.openapitools
openapi-generator-maven-plugin
4.3.1

okhttp dependency -

com.squareup.okhttp3
okhttp

OpenAPI declaration file content or url

N/A

Generation Details

Please refer steps defined below in "Steps to reproduce" section

Steps to reproduce

Step1 - Springfox generated contract with contentType text/plain

"/endPoint" : {
"post" : {
"tags" : [ "controller" ],
"summary" : "summary",
"operationId" : "operationId",
"requestBody" : {
"content" : {
"application/json" : {
"schema" : {
"type" : "string"
}
},
"text/plain" : {
"schema" : {
"type" : "string"
}
}
}
}

Step 2:
Generate client code using below Maven plugin for okhttp-gson library,
org.openapitools
openapi-generator-maven-plugin
4.3.1

Step3.
Invoke rest endpoint using generated client code.

Output: Below error message is thrown by the generatened ApiClient class in serialize method.

"Content type text/plain is not supported" for contentType text/plain"

Related issues/PRs

NA

Suggest a fix

NA

[fabiohecht]

Here is a workaround:

import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import javax.activation.MimeType;
import javax.activation.MimeTypeParseException;
import okhttp3.RequestBody;

public class MyApiClient extends ApiClient {
    @Override
    public RequestBody serialize(Object obj, String contentType) throws ApiException {

        try {
            MimeType contentMimeType = new MimeType(contentType);

            if ("text/plain".equals(contentMimeType.getBaseType()) && obj instanceof String) {
                obj = ((String) obj).getBytes(getCharset(contentMimeType));
            }

        } catch (MimeTypeParseException e) {
            throw new ApiException("Can't parse mime type: " + contentType);
        }

        return super.serialize(obj, contentType);
    }

    private Charset getCharset(MimeType contentMimeType) {
        String charsetParameter = contentMimeType.getParameter("charset");
        if (null == charsetParameter) {
            return StandardCharsets.UTF_8;
        }
        return Charset.forName(charsetParameter);
    }
}