在android工作室中没有得到输出有字符串请求但是在邮递员中得到了

Question

字符串请求返回null输出但在Postman中得到。当我使用jsonobject请求它会给出正确的输出。我不明白字符串请求有什么问题。

RequestQueue requestQueue = Volley.newRequestQueue（MainActivity.this）;         String URL =“http://demoangularaims.azurewebsites.net/api/v1/API_NI_ACD_FILL_COMMON_DDL_SP”;

    Log.d(TAG, " url=" + URL);
    StringRequest stringRequest = new StringRequest(Request.Method.POST, URL, new Response.Listener<String>() {
        @Override
        public void onResponse(String response) {
            Log.d(TAG, " response=" + response);
        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            Log.d(TAG, " error=" + error);

        }
    }) {
        @Override
        protected Map<String, String> getParams() throws AuthFailureError {

            LinkedHashMap<String, String> linkmap = new LinkedHashMap<>();
            linkmap.put("p_ENTITY_ID", "2");
            linkmap.put("p_ORGCD", "p01");
            linkmap.put("p_COMPCD", "A0002");
            linkmap.put("p_DIVCD", "");
            linkmap.put("p_USERID", "");
            linkmap.put("p_ACDYR", "");
            linkmap.put("p_TYPE", "ACDYR_DDL");
            linkmap.put("p_FILTER1", "");
            linkmap.put("p_FILTER2", "");
            linkmap.put("p_DEFUNCT", "");

            Log.d(TAG, " MAP=" + linkmap);
            return linkmap;
        }

        @Override
        public Map<String, String> getHeaders() throws AuthFailureError {
            LinkedHashMap<String, String> headers = new LinkedHashMap<>();
            return headers;
        }


    };

     requestQueue.add(stringRequest);

}