Java 415 http post request

Question

i'm in a big trouble with 415 error on http post request,

A fonctionnal guy gave me his test in postman and it works well :

{
    "variables": [],
    "info": {
        "name": "demo",
        "_postman_id": "id",
        "description": "",
        "schema": "https://schema.getpostman.com/json/collection/v2.0.0/collection.json"
    },
    "item": [
        {
            "name": "1 -getToken sandbox",
            "request": {
                "url": "myurl",
                "method": "POST",
                "header": [
                    {
                        "key": "Authorization",
                        "value": "Basic RTlBS000T0FtN1FORFc1SUxlRVFjeXZFTEZBYTpHTlB6ZVlaWXIyN2NDbG53Y1VvZ0ZiOGJWd2dh",
                        "description": ""
                    }
                ],
                "body": {
                    "mode": "urlencoded",
                    "urlencoded": [
                        {
                            "key": "grant_type",
                            "value": "password",
                            "description": "",
                            "type": "text"
                        },
                        {
                            "key": "username",
                            "value": "[user]",
                            "description": "",
                            "type": "text"
                        },
                        {
                            "key": "password",
                            "value": "[password]",
                            "description": "",
                            "type": "text"
                        }
                    ]
                },
                "description": ""
            },
            "response": []
        },

with the sent json, i received the bearer i wanted to receive.

In my java code, i have this :

String       postUrl       = "myurl";
            String dataTokenJson = "{\"grant_type\":\"password\", \"username\":\"myuser\", \"password\":\"mypassword\"}";
            
            
            
            Gson         gson          = new Gson();
            HttpClient   httpClient    = HttpClientBuilder.create().build();
            HttpPost     post          = new HttpPost(postUrl);

StringEntity postingString = new StringEntity(gson.toJson(dataTokenJson));

post.setEntity(postingString);
                post.addHeader("Content-Type","application/json");
                post.addHeader("Authorization","Basic RTlBS000T0FtN1FORFc1SUxlRVFjeXZFTEZBYTpHTlB6ZVlaWXIyN2NDbG53Y1VvZ0ZiOGJWd2dh");

HttpResponse  responseToken = httpClient.execute(post);

I tried to not using gson lib and set the StringEntity directly with the jsonString. I tried different methods to set the Header. Nothing works better.

so, I changed the content-type to "application/x-www-form-urlencoded" dont have 415 error anymore but 400.. I also tried to remove the content-type but it gave me a 415 again.

In fact, the server didnt except json but he is supposed to answer with a json.. The specifications wasnt clear

HttpResponseProxy{HTTP/1.1 400 Bad Request [Date: Fri, 18 Feb 2022 11:57:13 GMT, Server: Apache, Strict-Transport-Security: max-age=63072000; includeSubdomains;, X-Frame-Options: SAMEORIGIN, X-Frame-Options: DENY, X-Frame-Options: SAMEORIGIN, Strict-Transport-Security: max-age=63072000; includeSubdomains;, X-Content-Type-Options: nosniff, X-XSS-Protection: 1; mode=block, Content-Type: application/json, Connection: close, Transfer-Encoding: chunked] ResponseEntityProxy{[Content-Type: application/json,Chunked: true]}}