public static HTTPResponse uploadFile(Attachment file) {
        Rg_FileJSon jsonObj = new Rg_FileJSon();
        List<Rg_FileJSon.Files> Files = new List<Rg_FileJSon.Files>();
        Rg_FileJSon.Files jsonFile = new Rg_FileJSon.Files();
        jsonFile.name = file.Name;
        jsonFile.doctype = file.ContentType;
        jsonFile.data = String.valueOf(file.Body);
        Rg_FileJSon.Index ind = new Rg_FileJSon.Index();
        ind.name = 'index a';
        ind.typeId = 0;
        ind.value = '1';
        jsonFile.Index = new List<Rg_FileJSon.Index>{ind};
        Files.add(jsonFile);
        jsonObj.files = Files;
        HttpRequest req = new HttpRequest();
        req.setHeader('Content-Type','application/json');
        req.setMethod('POST');
        req.setEndpoint('https://saas.docufree.com/dfwebservice/v3/files/capture/folder?targetId=3486');
        req.setBody(body);
        req.setTimeout(60000);
        Rg_FileUploadService obj = new Rg_FileUploadService();
        string accessToken = obj.genAccessToken();
        req.setHeader('Authorization','Bearer ' + accessToken);
        System.debug('request : '+req.getBody());
        Http http = new Http();
        return http.send(req);
    }

//JSON Class
public class Rg_FileJSon {
    public class Index {
        public Integer typeId;
        public String name;
        public String value;
    }
    public class Files {
        public String name;
        public String data;
        public String doctype;
        public List<Index> index;
    }
    public List<Files> files;
    public Integer bindFileId;
    public static Rg_FileJSon parse(String json) {
        return (Rg_FileJSon) System.JSON.deserialize(json, Rg_FileJSon.class);
    }
}