自己拼接json字符串，现在用Gson来实现

 StringBuilder stringBuilder = new StringBuilder("[");
         String ssString;
         ArrayList<CompetitionsByCity> ccs =competitionMapper.getCmptList(hashMap);

 for (CompetitionsByCity tmp:ccs)
         {

             stringBuilder.append("{\"cmptId\":"+"\""+tmp.getCmptId()+"\""+","+"\"cmptName\":"+"\""+tmp.getCmptName()+"\""+","+
                     "\"duration\":"+"\""+tmp.getDuration()+"\""+","+"\"cmptStarLevel\":"+"\""+tmp.getCmptStarLevel()+"\""+","+"\"cmptCapacity\":"+"\""+tmp.getCmptCapacity()+"\""+","+"\"cmptLength\":"+"\""+tmp.getCmptLength()+"\""+
                     "\"cmptFavorByMe\":"+"\""+"0"+"\""+","+"\"imgId\":"+"\""+tmp.getImgId()+"\""+"},"); 

             //stringBuilder.append(stringBuilder);

         }

下面是使用Gson

 String ssString;
         ArrayList<CompetitionsByCity> ccs = competitionMapper
                 .getCmptList(hashMap);
         Gson gson = new Gson();
         String str = gson.toJson(ccs);
         ssString = "\"size\":" + ccs.size() + "," + "\"cmptList\":" + str;
         return ssString;