请求中缺少Grant_type

Question

我正在尝试对Dynamics 365进行令牌访问（协议oauth2）。

这是构建和执行http post请求的代码：

URI uri = new URIBuilder()
                    .setScheme("https")
                    .setHost("login.microsoftonline.com")
                    .setPath("/"+PropertyUtils.getInstance().getProperty("AD_TENANT_ID")+"/oauth2/token")
                    .setParameter("grant_type", "client_credentials")
                    .setParameter("client_id", PropertyUtils.getInstance().getProperty("CLIENT_ID"))
                    .setParameter("resource", PropertyUtils.getInstance().getProperty("RESOURCE"))
                    .setParameter("client_secret", PropertyUtils.getInstance().getProperty("CLIENT_SECRET"))
                    .build();
            HttpPost post = new HttpPost(uri);
            HttpResponse response = client.execute(post);

响应json是：

{"error":"invalid_request","error_description":"AADSTS900144: The request body must contain the following parameter: 'grant_type'.\r ...

为什么响应告诉我Grant_type在请求中作为参数丢失？