from scrapy.http import HtmlResponse
from scrapy.http import Requestclass Md1(object):@classmethoddef from_crawler(cls, crawler):# 此方法用于拿到当前的爬虫s = cls()return sdef process_request(self, request, spider):    print('md1.process_request',request)return None # 返回如果是 空就会继续往下执行下一个中间件的 process_request 方法，如果一旦有返回值就要考虑情况"""# 1. 返回 Response# 返回 Response 之后会往下执行 最后一个中间件的 process_response 方法 # import requests# result = requests.get(request.url)# return HtmlResponse(url=request.url, status=200, headers=None, body=result.content)# 2. 返回 Request# 返回 Request 之后 相当于无视了这次的请求 重新回到 调制器 那边，相当于又产生了新的任务# return Request('https://dig.chouti.com/r/tec/hot/1')# 3. 抛出异常    # 抛出异常 必须要 有 process_exception 方法进行捕捉异常，不然会报错# process_exception 方法在进行一系列的操作 在捕捉到异常的时候 # from scrapy.exceptions import IgnoreRequest# raise IgnoreRequest# 4. 对请求进行加工(*) # 通常我们都是用于对请求加工，然后再继续下面操作不返回东西 # request.headers['user-agent'] = "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36"# return None"""def process_response(self, request, response, spider):# Called with the response returned from the downloader.# Must either;# - return a Response object    # 返回一个 Response 来代替当前的 Response# - return a Request object        # 返回一个 Request 开启新任务 # - or raise IgnoreRequest        # 返回一个 IgnoreRequest 进行异常捕捉 print('m1.process_response',request,response)return responsedef process_exception(self, request, exception, spider):# Called when a download handler or a process_request()# (from other downloader middleware) raises an exception.# Must either:# - return None: continue processing this exception# 通常我们都是直接返回 None 就可以了# - return a Response object: stops process_exception() chain    # 只要返回了 Response 当前的 process_exception 就不做操作了 # 返回 Response 表示交给下一个 中间件的 process_exception 继续处理 # - return a Request object: stops process_exception() chain    # 只要返回了 Request 当前的 process_exception 就不做操作了 # 返回 Request 放弃本次任务，新建任务     pass

DOWNLOADER_MIDDLEWARES = {    #'xdb.middlewares.XdbDownloaderMiddleware': 543,# 'xdb.proxy.XdbProxyMiddleware':751,'xdb.md.Md1':666,    # 依旧是 0-1000 越小越优先 'xdb.md.Md2':667,
}

调度器 给 下载器的时候先走 process_request（从第一个中间件往最后一个走） 然后如果根据返回情况进行判断接下来的方向返回 None 继续下一个中间件的 process_request返回 Response 进入 最后一个下载中间件的 process_response 流程返回 Request 返回 调度器开启新任务 返回 异常  进入当前中间件的 process_exception 进行异常处理
下载器 还给 爬虫的时候要走 process_response（从最后一个中间件往第一个走）然后如果根据返回情况进行判断接下来的方向返回 None 继续上一个中间件的 process_response返回 Response 替换当前Response 进入上一个下载中间件的 process_response 流程返回 Request 返回 调度器开启新任务 放弃当前的任务  返回 异常  进入当前中间件的 process_exception 进行异常处理

from fake_useragent import UserAgent

RANDOM_UA_TYPE = "random"

class RandomUserAgentMiddlware(object):# 随机更换user-agentdef __init__(self, crawler):super(RandomUserAgentMiddlware, self).__init__()self.ua = UserAgent()self.ua_type = crawler.settings.get("RANDOM_UA_TYPE", "random")@classmethoddef from_crawler(cls, crawler):return cls(crawler)def process_request(self, request, spider):def get_ua():return getattr(self.ua, self.ua_type)request.headers.setdefault('User-Agent', get_ua())

# -*- coding: utf-8 -*-
import requests
from scrapy.selector import Selector
import pymysqlconn = pymysql.connect(host="127.0.0.1", user="root", passwd="root", db="article_spider", charset="utf8")
cursor = conn.cursor()def crawl_ips():# 爬取西刺的免费ip代理headers = {"User-Agent": "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Firefox/52.0"}for i in range(1568):re = requests.get("http://www.xicidaili.com/nn/{0}".format(i), headers=headers)selector = Selector(text=re.text)all_trs = selector.css("#ip_list tr")ip_list = []for tr in all_trs[1:]:speed_str = tr.css(".bar::attr(title)").extract()[0]if speed_str:speed = float(speed_str.split("秒")[0])all_texts = tr.css("td::text").extract()ip = all_texts[0]port = all_texts[1]proxy_type = all_texts[5]ip_list.append((ip, port, proxy_type, speed))for ip_info in ip_list:cursor.execute("insert proxy_ip(ip, port, speed, proxy_type) VALUES('{0}', '{1}', {2}, 'HTTP')".format(ip_info[0], ip_info[1], ip_info[3]))conn.commit()class GetIP(object):def delete_ip(self, ip):# 从数据库中删除无效的ipdelete_sql = """delete from proxy_ip where ip='{0}'""".format(ip)cursor.execute(delete_sql)conn.commit()return Truedef judge_ip(self, ip, port):# 判断ip是否可用http_url = "http://www.baidu.com"proxy_url = "http://{0}:{1}".format(ip, port)try:proxy_dict = {"http": proxy_url,}response = requests.get(http_url, proxies=proxy_dict)except Exception as e:print("invalid ip and port")self.delete_ip(ip)return Falseelse:code = response.status_codeif code >= 200 and code < 300:print("effective ip")return Trueelse:print("invalid ip and port")self.delete_ip(ip)return Falsedef get_random_ip(self):# 从数据库中随机获取一个可用的iprandom_sql = """SELECT ip, port FROM proxy_ipORDER BY RAND()LIMIT 1"""result = cursor.execute(random_sql)for ip_info in cursor.fetchall():ip = ip_info[0]port = ip_info[1]judge_re = self.judge_ip(ip, port)if judge_re:return "http://{0}:{1}".format(ip, port)else:return self.get_random_ip()# print (crawl_ips())
if __name__ == "__main__":get_ip = GetIP()get_ip.get_random_ip()

class RandomProxyMiddleware(object):# 动态设置ip代理def process_request(self, request, spider):get_ip = GetIP()request.meta["proxy"] = get_ip.get_random_ip()

class Sd1(object):# Not all methods need to be defined. If a method is not defined,# scrapy acts as if the spider middleware does not modify the# passed objects.
@classmethoddef from_crawler(cls, crawler):# This method is used by Scrapy to create your spiders.s = cls()return sdef process_spider_input(self, response, spider):# Called for each response that goes through the spider# middleware and into the spider.# Should return None or raise an exception.return Nonedef process_spider_output(self, response, result, spider):# Called with the results returned from the Spider, after# it has processed the response.# Must return an iterable of Request, dict or Item objects.for i in result:yield idef process_spider_exception(self, response, exception, spider):# Called when a spider or process_spider_input() method# (from other spider middleware) raises an exception.# Should return either None or an iterable of Response, dict# or Item objects.pass# 只在爬虫启动时，执行一次。def process_start_requests(self, start_requests, spider):# Called with the start requests of the spider, and works# similarly to the process_spider_output() method, except# that it doesn’t have a response associated.# Must return only requests (not items).for r in start_requests:yield r

SPIDER_MIDDLEWARES = {# 'xdb.middlewares.XdbSpiderMiddleware': 543,'xdb.sd.Sd1': 666,    # 同爬虫中间件一样的判断机制 'xdb.sd.Sd2': 667,
}

from scrapy import signalsclass MyExtend(object):def __init__(self):pass@classmethoddef from_crawler(cls, crawler):self = cls()crawler.signals.connect(self.x1, signal=signals.spider_opened) # 绑定信号发生时允许的函数crawler.signals.connect(self.x2, signal=signals.spider_closed)return selfdef x1(self, spider):print('open')def x2(self, spider):print('close')

# 信号可选类型  from scrapy import signals 中可以看到
engine_started = object()
engine_stopped = object()spider_opened = object()
spider_idle = object()
spider_closed = object()
spider_error = object()request_scheduled = object()
request_dropped = object()
response_received = object()
response_downloaded = object()item_scraped = object()
item_dropped = object()

# settings.py 

EXTENSIONS = {'xdb.ext.MyExtend':666,}

import sys
from scrapy.cmdline import executeif __name__ == '__main__':execute(["scrapy","crawl","chouti","--nolog"])

- 在spiders同级创建任意目录，如：commands
- 在其中创建 crawlall.py 文件 （此处文件名就是自定义的命令）
- 在settings.py 中添加配置 COMMANDS_MODULE = '项目名称.目录名称'
- 在项目目录执行命令：scrapy crawlall 

# crawlall.py

from scrapy.commands import ScrapyCommand
from scrapy.utils.project import get_project_settingsclass Command(ScrapyCommand):requires_project = Truedef syntax(self):return '[options]'def short_desc(self):return 'Runs all of the spiders'def run(self, args, opts):spider_list = self.crawler_process.spiders.list()for name in spider_list:self.crawler_process.crawl(name, **opts.__dict__)self.crawler_process.start()

# settings.py

COMMANDS_MODULE  = "xdb.commands"

scrapy crawl lagou -s JOBDIR=job_info/001

JOBDIR="job_info/001"

cutom_settings = {"JOBDIR": "job_info/001"
}