Httpclient获取网络JSON get可以而post出错

HttpClient  httpClient=new DefaultHttpClient();
HttpGet  httpGet=new HttpGet(
"http://route.showapi.com/9-7"+"?"+"area=北京&areaid=&month=201606&showapi_appid=22661&showapi_sign=fa597c55d97d435ebbc67bc9dd45fe83");
HttpResponse response = httpClient.execute(httpGet);
int code = response.getStatusLine().getStatusCode();
if(code== HttpStatus.SC_OK){
HttpEntity entity = response.getEntity()
String s1 = EntityUtils.toString(entity, "utf-8");
System.out.println(s1);
}

这个是post的

HttpClient httpClient = new DefaultHttpClient();
        HttpPost httpPost=new HttpPost("http://route.showapi.com/9-7");
        
        List<BasicNameValuePair>  list=new ArrayList<BasicNameValuePair>();
        list.add(new BasicNameValuePair("showapi_sign","fa597c55d97d435ebbc67bc9dd45fe83"));
        list.add(new BasicNameValuePair("showapi_appid","22661"));
        list.add(new BasicNameValuePair("area","北京"));
        list.add(new BasicNameValuePair("month","201607"));
    
        UrlEncodedFormEntity entity = new UrlEncodedFormEntity(list);
        httpPost.setEntity(entity);
        HttpResponse response = httpClient.execute(httpPost);
        if(response.getStatusLine().getStatusCode()== HttpStatus.SC_OK){
            HttpEntity entity1 = response.getEntity();
            String s1 = EntityUtils.toString(entity1, "utf-8");
            System.out.println(s1);
        }

get得到的数据正确
post得到
{“showapi_res_code”:-3,”showapi_res_error”:”系统异常。读取错误。”,”showapi_res_body”:{}}