(一)存储到mongodb:
1.创建一个client对象，调用pymongo的MongoClient()方法，并传入数据库的url,使用client[db名]创建一个数据库db，
调用db[collection名],创建一个表coll,调用coll.insert(dict对象)插入数据。
# class MongoPipeline(object):
#
# def __init__(self,mongo_url,mongo_db):
# self.mongo_url = mongo_url
# self.mongo_db = mongo_db
#
# @classmethod
# def from_crawler(cls,crawler):
# return cls (
# mongo_url=crawler.settings.get('MONGO_URL'),
# mongo_db =crawler.settings.get('MONGO_DB')
# )
# def open_spider(self,spider):
# self.clict = pymongo.MongoClient(self.mongo_url)
# self.db = self.clict[self.mongo_db]
#
# def process_item(self,item,spider):
# name = self.__class__.__name__
# self.db[name].insert(dict(item))
# return item
# def close_spider(self,spider):
# self.clict.close()
