java - HTTP Post は機能しますが、GET は機能しません

Question

ログイン システムに parse.com の REST API を使用しています (API: https://parse.com/docs/rest#users-signup )。

問題は、登録作業中です。

        JSONObject json = new JSONObject();
    json.put("username", username);
    json.put("password", password);
    json.put("email", email);
    HttpClient httpclient = new DefaultHttpClient();
    HttpPost httppost = new HttpPost(Reference.PARSE_API_URL
            + Reference.PARSE_API_USERS);
    httppost.addHeader("X-Parse-Application-Id", Reference.APP_ID);
    httppost.addHeader("X-Parse-REST-API-Key", Reference.REST_API_KEY);
    httppost.addHeader("Content-Type", "application/json");
    httppost.setEntity(new StringEntity(json.toString()));
    HttpResponse httpresponse = httpclient.execute(httppost);
    System.out.println(httpresponse.getStatusLine());

ログインシステムはそうではありません（サイトが言うようにデータを暗号化します）：

            JSONObject jsonadd = new JSONObject();
        jsonadd.put("username", username);
        jsonadd.put("password", password);

        HttpClient httpclient = new DefaultHttpClient();
        HttpGet httpget = new HttpGet(Reference.PARSE_API_URL + Reference.PARSE_API_LOGIN + "?" + URLEncoder.encode(jsonadd.toString(), "UTF-8"));
        httpget.addHeader("X-Parse-Application-Id", Reference.APP_ID);
        httpget.addHeader("X-Parse-REST-API-Key", Reference.REST_API_KEY);
        HttpResponse httpresponse = httpclient.execute(httpget);
        System.out.println(httpresponse.getStatusLine());

そして、これらは参照変数です:

    public static final String APP_ID = "(HIDDEN)";
public static final String REST_API_KEY = (HIDDEN)";

public static final String VERSION_CLASS_NAME = "version";

public static final String PARSE_API_URL = "https://api.parse.com";
public static final String PARSE_API_URL_CLASSES = "/1/classes/";
public static final String PARSE_API_USERS = "/1/users";
public static final String PARSE_API_LOGIN = "/1/login";

エラー: HTTP/1.1 400 Bad Request