BULK 2.0 Activity Export in java getting 400 HTTP status code

Am calling to Bulk 2.0 API to get the details for Activity Export in java, but am getting the HTTP status code 400 with error response.

URL:https://secure.p03.eloqua.com/API/Bulk/2.0/activities/exports

Input JSON :

{"filter":"'{{Activity.Type}}'='EmailClickthrough' and '{{Activity.CreatedAt}}'>='2014-01-02 11:42:01'","name":"Bulk Activity Export","dataRetentionDuration":"PT1H","fields":{"ActivityId":"{{Activity.Id}}","AssetType":"{{Activity.Asset.Type}}","EmailWebLink":"{{Activity.Field(EmailWebLink)}}","ActivityDate ":"{{Activity.CreatedAt}}","VisitorId":"{{Activity.Visitor.Id}}","ActivityType":"{{Activity.Type}}","IpAddress":"{{Activity.Field(IpAddress)}}","SubjectLine":"{{Activity.Field(SubjectLine)}}","AssetName":"{{Activity.Asset.Name}}","EmailRecipientId":"{{Activity.Field(EmailRecipientId)}}","EmailAddress":"{{Activity.Field(EmailAddress)}}","VisitorExternalId":"{{Activity.Visitor.ExternalId}}","ContactId":"{{Activity.Contact.Id}}","AssetId":"{{Activity.Asset.Id}}"}}

Output :

Status code: 400

Output JSON :

{"failures":[{"field":"fields","stackTrace":[],"value":"ActivityDate ","constraint":"Must start with an alpha or underscore character and can only contain alphanumeric and underscore characters (ie match /^[_a-zA-Z][_0-9a-zA-Z]*$/)."}]}

Here am adding the java code to API call

            URL url = new URL(_baseUrl);

            Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress(<oracle proxy which i removed>));

HttpURLConnection conn = (HttpURLConnection) url.openConnection(proxy);

                        conn.setInstanceFollowRedirects(false);

                        conn.setRequestMethod(method.toString());

                        conn.setRequestProperty("Content-Type", "application/json");

                        conn.setRequestProperty("Accept", "application/json");

                        conn.setConnectTimeout(getConTimeOut()*60*1000); /* 60*1000=> 1 min in milliseconds * number of minutes (max time taken to establish connection) */

                        conn.setReadTimeout(getConTimeOut()*60*1000); /* the max idle time between connection establishment and the response packet received */

                        conn.setRequestProperty("Authorization", _authToken);

                        conn.addRequestProperty("User-Agent", "Mozilla/5.0 (compatible; MSIE 5.5; Windows NT 4.0)");

            if (method == Method.POST || method == Method.PUT) {

                conn.setDoOutput(true);

                final OutputStream os = conn.getOutputStream();

                os.write(body.getBytes());

                os.flush();

                os.close();

            }

            InputStream is = null;

            if (conn.getResponseCode() == 200) {

                is = conn.getInputStream();

            } else {

                /* error from server */

                is = conn.getErrorStream();

            }

However by using above code am able to fetch other API (Rest and Bulk) 1.0 calls, but am not able to get for above Bulk 2.0 API call.