public String post(final String url, final String json, final Headers headers) throws IOException {
        RequestBody body = RequestBody.create(JSON, json);
        Request request = new Request.Builder()
                .headers(headers)
                .url(url)
                .post(body)
                .build();
        return client.newCall(request).execute().body().string();
    }
Post string.

@param url     the url
@param json    the json
@param headers the headers
@return the string
@throws IOException the io exception
shenyu-register-center/shenyu-register-client/shenyu-register-client-http/src/main/java/org/apache/shenyu/register/client/http/utils/OkHttpTools.java