1 如果没有看过scrapy的朋友，可以到scrapy的官网看一下再来看这篇文章

   2 创建一个scrapy的项目，请看http://blog.csdn.net/chenguolinblog/article/details/19699865

   3 下面我们就一个一个文件的来分析，最后我会给出GitHub上面的源码

（1）第一个文件 spidr.py，这个文件的作用就是我们自己定义的蜘蛛，用来爬取网页的，具体看以下的注释

__author__ = 'chenguolin'
"""
Date: 2014-03-06
"""

from scrapy.contrib.linkextractors.sgml import SgmlLinkExtractor
from scrapy.contrib.spiders import CrawlSpider, Rule        #这个是预定义的蜘蛛，使用它可以自定义爬取链接的规则rule
from scrapy.selector import HtmlXPathSelector               #导入HtmlXPathSelector进行解析
from firstScrapy.items import FirstscrapyItem

class firstScrapy(CrawlSpider):
    name = "firstScrapy"                                    #爬虫的名字要唯一
    allowed_domains = ["yuedu.baidu.com"]                   #运行爬取的网页
    start_urls = ["http://yuedu.baidu.com/book/list/0?od=0&show=1&pn=0"]   #第一个爬取的网页
    #以下定义了两个规则，第一个是当前要解析的网页，回调函数是myparse；第二个则是抓取到下一页链接的时候，不需要回调直接跳转
    rules = [Rule(SgmlLinkExtractor(allow=('/ebook/[^/]+fr=booklist')), callback='myparse'),
             Rule(SgmlLinkExtractor(allow=('/book/list/[^/]+pn=[^/]+', )), follow=True)]

    #回调函数
    def myparse(self, response):
        x = HtmlXPathSelector(response)
        item = FirstscrapyItem()

        # get item
        item['link'] = response.url
        item['title'] = ""
        strlist = x.select("//h1/@title").extract()
        if len(strlist) > 0:
            item['title'] = strlist[0]
        # return the item
        return item

from scrapy.item import Item, Field

class FirstscrapyItem(Item):
    title = Field(serializer=str)
    link = Field(serializer=str)

# Define your item pipelines here
#
# Don't forget to add your pipeline to the ITEM_PIPELINES setting
# See: http://doc.scrapy.org/en/latest/topics/item-pipeline.html

from twisted.enterprise import adbapi              #导入twisted的包
import MySQLdb
import MySQLdb.cursors

class FirstscrapyPipeline(object):
    def __init__(self):                            #初始化连接mysql的数据库相关信息
        self.dbpool = adbapi.ConnectionPool('MySQLdb',
                db = 'bookInfo',
                user = 'root',
                passwd = '123456',
                cursorclass = MySQLdb.cursors.DictCursor,
                charset = 'utf8',
                use_unicode = False
        )

    # pipeline dafault function                    #这个函数是pipeline默认调用的函数
    def process_item(self, item, spider):
        query = self.dbpool.runInteraction(self._conditional_insert, item)
        return item

    # insert the data to databases                 #把数据插入到数据库中
    def _conditional_insert(self, tx, item):
        sql = "insert into book values (%s, %s)"
        tx.execute(sql, (item["title"], item["link"]))