<form method='POST' action="/page.jsp"  >
            <input type='text' name='login' placeholder='Login' /><br/>
            <input type='password' name='pass' placeholder='Password'    ><br/>
            <input type='submit' value='Вход' />
        </form>

   try {
            CloseableHttpClient httpclient = HttpClients.createDefault();
            HttpPost httppost = new HttpPost("http://redbob.ru/test/xx");

            List<NameValuePair> params = new ArrayList<>(2);
            params.add(new BasicNameValuePair("pass", "admin"));
            params.add(new BasicNameValuePair("login", "admin"));
            httppost.setEntity(new UrlEncodedFormEntity(params, "UTF-8"));
            CloseableHttpResponse response = httpclient.execute(httppost);
            HttpEntity entity = response.getEntity();
            
            InputStream instream = entity.getContent();
        } catch (UnsupportedEncodingException ex) {
             ex.printStackTrace();
        } catch (IOException ex) {
             ex.printStackTrace();
        }