实际上
application/json，您不是在发布实体，而是在发布具有
application/x-www-form-urlenpred单个值对json =（enpred json）的HTTP表单实体（）。
代替
List<NamevaluePair> namevaluePairs = new ArrayList<NamevaluePair>(2); namevaluePairs.add(new BasicNamevaluePair("json", j.toString()));httppost.setEntity(new UrlEnpredFormEntity(namevaluePairs));尝试
httppost.setEntity(new StringEntity(j.toString(),"application/json","UTF-8"));
