如何在android web服务中发布xml数据的主体？

Question

我正在尝试使用volley api将带有xml正文的请求发布到Web服务，但它返回的输出类似于无效的凭据。我是我的代码

StringRequest stringRequest = new StringRequest(Request.Method.POST, url, new com.android.volley.Response.Listener<String>() {
            @Override
            public void onResponse(String s) {
                Log.e("onResponse","...."+s);
            }
        }, new com.android.volley.Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError volleyError) {
                Log.e("onErrorResponse","...."+volleyError);
            }
        }) {
            @Override
            public String getBodyContentType() {
                return "application/xml; charset=" +
                        getParamsEncoding();
            }

            @Override
            protected Map<String, String> getParams() {
                Map<String, String> params = new HashMap<String, String>();
                params.put("SLUsername", "uname");
                params.put("SLPassword", "pwd");
                params.put("CurrentDate", "date");
                return params;
            }


        };



// Schedule the request on the queue
        queue.add(stringRequest);
    }

下面是我的样本xml正文

<GetDetails>
<SLUsername>Settings Username</SLUsername>
<SLPassword>Settings Password</SLPassword>
<CurrentDate>Settings Date</CurrentDate>
</GetDetails>

如何将此xml主体发送到api？