如何在 android post request 上将 json 数组添加到 madrill API

我正在使用这个php代码发送电子邮件，它可以工作

$uri = 'https://mandrillapp.com/api/1.0/messages/send.json';
$postString = '{
"key": "mykey",
"message": {
"html": "this is the emails html content",
"text": "this is the emails text content",
"subject": "this is the subject",
"from_email": "gwapp@outlook.es",
"from_name": "GW",
"to": [
    {
        "email": "el_nota_5@hotmail.com",
        "name": "Alvaro"
    }
],
"headers": {
},
"track_opens": true,
"track_clicks": true,
"auto_text": true,
"url_strip_qs": true,
"preserve_recipients": true,
"merge": true,
"global_merge_vars": [
],
"merge_vars": [
],
"tags": [
],
"google_analytics_domains": [
],
"google_analytics_campaign": "...",
"metadata": [
],
"recipient_metadata": [
],
"attachments": [
]
},
   "async": false
}';
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $uri);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true );
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true );
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $postString);
$result = curl_exec($ch);

我想在 android 上发出发布请求，但我不知道我必须将电子邮件 json 数组放在哪里

protected String doInBackground(String... params) {
        String path ="https://mandrillapp.com/api/1.0/messages/send.json";
        String json ="{...email information}"
        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost(path);
        try {
               //How i have to add te json string??
               httpclient.execute(httppost);
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
}

我如何在帖子请求中发送带有电子邮件信息的 json 字符串？