Fastjson toJSONString用单引号进行转换
String str = '[{"sourceItemId":"5548696","itemTitle":"服务商测试商品不发货","itemCount":"1","itemCountMax":""},{"sourceItemId":"554314455","itemTitle":"测试店铺不发货","itemCount":"1","itemCountMax":""}]';
JSONArray _list_item_ids_update = JSON.parseArray(request.getParameter("_list_item_ids"));
JSON.toJSONString(_list_item_ids_update,SerializerFeature.UseSingleQuotes);