介绍
介绍
福哥更新了Spider对象,实现了爬取网页内容,分析网页数据,写入数据库这些功能。实现了这些功能之后网页蜘蛛的基本功能也就差不多完成了!后面就可以开始编写搜索引擎的前端UI功能了,相对网页蜘蛛来说,搜索引擎前端UI就比较简单了!
但是,网页蜘蛛是搜索引擎的基础,只有采集到足够多的数据,搜索引擎才可以在也会查询的时候返回用户想看到的结果内容。所以,今天这一课童鞋们一定要好好学习了!
增加字段
在前面设计数据表的时候出了一个纰漏,福哥没有在webpages数据表里建立与websites数据表的关联键,这样就无法在webpages里提取一个域名下的所有网页信息了。
新增字段
我们需要在webpages数据表里增加关联键字段websiteId用来关联websites数据表的主键字段。
SQL
SQL语句如下
mysql> alter table webpages add column websiteId int not null after webpageId, add key websiteId (websiteId);
Query OK, 0 rows affected (0.18 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql>
Spider对象
方法
getPendingPages
def getPendingPages(self, domainName, nums):
try:
self.mysqlCS.execute("SELECT * FROM websites WHERE domainName = %s", [domainName])
row = self.mysqlCS.fetchone()
if row is not None:
websiteId = row[0]
self.mysqlCS.execute("SELECT * FROM webpages WHERE websiteId = %s ORDER BY lastFetchDT DESC LIMIT %s", [websiteId, nums])
rows = self.mysqlCS.fetchall()
return rows
except Exception as e:
print ("Fail to getPendingPages")
print e
self.mysqlCN.rollback()
return None
analyzePage
def analyzePage(self, url):
title = self.chrome.title
keywords = ""
description = ""
charset = ""
pageSource = self.chrome.page_source
stRE = re.compile("<\/?[a-z0-9]+[^\>]*>", re.M | re.I)
scriptRE = re.compile("<(script).*?>[\s\S]*?<\/\1>", re.M | re.I)
bcRE = re.compile("[\s\t\r\n]+", re.M | re.I)
pageText = self.chrome.page_source.encode("gbk", "ignore")
pageText = re.sub(stRE, " ", pageText)
pageText = re.sub(scriptRE, " ", pageText)
pageText = re.sub(bcRE, " ", pageText)
pageText = pageText.decode("gbk")
metas = self.chrome.find_elements_by_tag_name("meta")
for meta in metas:
myName = meta.get_attribute("name")
myContent = meta.get_attribute("content")
myHttpEquiv = meta.get_attribute("http-equiv")
if myName == "keywords":
keywords = myContent
elif myName == "description":
description = myContent
elif myHttpEquiv is not None and myHttpEquiv.lower() == "content-type":
myCharset = myContent
csRE = re.compile("charset\=([^\;]+)", re.M | re.I)
mats = csRE.search(myCharset)
if mats:
charset=mats.group(1).lower()
return {"url": url, "title": title, "keywords": keywords, "description": description, "charset": charset, "pageText":pageText}
findAllATags
def findAllATags(self, websiteId, domainName):
links = self.chrome.find_elements_by_tag_name("a")
for link in links:
try:
myHref = link.get_attribute("href").encode("gbk")
myWebPageType = self.isWebPage(myHref, domainName)
if myWebPageType == 1:
ret = self.saveWebPage(websiteId, myHref)
elif myWebPageType == 2:
lnkRE = re.compile("^(http|https)\:\/\/([^\/]+)", re.M | re.I)
mats = lnkRE.search(myHref)
if mats:
ret = self.saveDomainPage(mats.group(2).lower())
except Exception as e:
doNothing = e
fetchDomainURL
def fetchDomainURL(self, websiteId, domainName):
# open page of domain
url = "http://" + domainName
print ("打开网址:" + url)
self.chrome.get(url)
# find all A tags
self.findAllATags(websiteId, domainName)
fetchWebURL
def fetchWebURL(self, websiteId, domainName, url):
# open page of url
print ("打开网址:" + url)
self.chrome.get(url)
# find all A tags
self.findAllATags(websiteId, domainName)
fetchDomainPageURL
def fetchDomainPageURL(self, websiteId, domainName, webpageId, url):
# open page of url
print ("打开网页: " + url)
self.chrome.get(url)
# analyze page
print ("分析网页: " + url)
args = self.analyzePage(url)
# save web page full data
self.updateWebPage(webpageId, args)
# find all A tags
self.findAllATags(websiteId, domainName)
saveWebPage
def saveWebPage(self, websiteId, url):
# try to insert url into webpages
try:
self.mysqlCS.execute("SELECT * FROM webpages WHERE url = %s", [url])
row = self.mysqlCS.fetchone()
if row is None:
self.mysqlCS.execute("INSERT INTO webpages (websiteId, url, statusCode, charset, createDT) VALUES (%s, %s, %s, %s, now())", [websiteId, url, 200, 1])
self.mysqlCN.commit()
print ("保存网页: " + url)
return self.mysqlCS.lastrowid
else:
return row[0]
except Exception as e:
print ("Fail to saveWebPage")
print e
return None
updateWebPage
def updateWebPage(self, webpageId, args):
try:
self.mysqlCS.execute("UPDATE webpages SET title = %s, keywords = %s, description = %s, lastFetchDT = now() WHERE webpageId = %s",
[args["title"], args["keywords"].encode("utf-8"), args["description"].encode("utf-8"), webpageId])
self.mysqlCN.commit()
print ("更新网页: " + args["url"])
return webpageId
except Exception as e:
print ("Failed to updateWebPage")
print e
return None
主程序
主程序代码也有所更新,除了之前进行的域名爬取处理之外,还增加了对域名下面的网页的爬取处理。
from lib.Spider import *
mySpider = Spider()
mySpider.open()
domains = mySpider.getPendingDomains(10)
if domains is not None:
for domain in domains:
mySpider.fetchDomainURL(domain[0], domain[1])
pages = mySpider.getPendingPages(domain[1], 100)
if pages is not None:
for page in pages:
mySpider.fetchDomainPageURL(domain[0], domain[1], page[0], page[2])
mySpider.close()
讲解
getPendingPages
通过域名获取到websites数据表的相关记录
通过websites.websiteId字段的值在webpages表里查询出指定数量的该域名所属的网页信息
analyzePage
使用正则表达式将meta信息里面的charset信息提取出来了
findAllATags
增加了websiteId参数,传递给saveWebPage方法
fetchDomainURL
增加了websiteId参数,传递给findAllATags方法
fetchWebURL
增加了websiteId参数,传递给findAllATags方法
fetchDomainPageURL
打开指定的url的网页
分析网页的信息,包括标题、关键字、描述等等信息
将网页的信息更新到webpages数据表里面
扫描网页的超链接,提取子级页面网址
saveWebPage
增加了websiteId参数,在写入webpages数据表的时候传递websiteId参数
updateWebPage
根据webpageId更新webpages数据表的相关字段的值
总结
我们的网页蜘蛛已经完成80%以上了,剩下的就是把网页的文字数据提取出来写入到数据库当中,同时将数据库当中的网页数据同步到ElasticSearch搜索引擎里面,采集的工作就算基本完成了!
下一节课,福哥将带着大家完成网页蜘蛛的最后一部分代码的编写,大家要好好学习哦~~
P.S.
微信公众号的文章发出去之后是不能编辑的,但是福哥偶尔会修复一些描述不到位、示例不正确、结构不清晰等等的文章错误,这些只能在网站上才能看到最新版本内容,望大家知晓~~
https://m.tongfu.net/home/35/blog/512811.html