scrapy中间件

scrapy中间有两种：爬虫中间件，下载中间件

爬虫中间件：处于引擎和爬虫spider之间

下载中间件：处于引擎和下载器之间

主要对下载中间件进行处理

下载中间件

作用：批量拦截请求和响应

拦截请求

UA伪装：将所有的请求尽可能多的设定成不同的请求载体身份标识

request.headers['User-Agent'] = 'xxx'

需要构建一个请求载体池：

user_agent_list = [
        "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.1 "
        "(KHTML, like Gecko) Chrome/22.0.1207.1 Safari/537.1",
        "Mozilla/5.0 (X11; CrOS i686 2268.111.0) AppleWebKit/536.11 "
        "(KHTML, like Gecko) Chrome/20.0.1132.57 Safari/536.11",
        "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.6 "
        "(KHTML, like Gecko) Chrome/20.0.1092.0 Safari/536.6",
        "Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.6 "
        "(KHTML, like Gecko) Chrome/20.0.1090.0 Safari/536.6",
        "Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.1 "
        "(KHTML, like Gecko) Chrome/19.77.34.5 Safari/537.1",
        "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/536.5 "
        "(KHTML, like Gecko) Chrome/19.0.1084.9 Safari/536.5",
        "Mozilla/5.0 (Windows NT 6.0) AppleWebKit/536.5 "
        "(KHTML, like Gecko) Chrome/19.0.1084.36 Safari/536.5",
        "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1063.0 Safari/536.3",
        "Mozilla/5.0 (Windows NT 5.1) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1063.0 Safari/536.3",
        "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_0) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1063.0 Safari/536.3",
        "Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1062.0 Safari/536.3",
        "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1062.0 Safari/536.3",
        "Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1061.1 Safari/536.3",
        "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1061.1 Safari/536.3",
        "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1061.1 Safari/536.3",
        "Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.3 "
        "(KHTML, like Gecko) Chrome/19.0.1061.0 Safari/536.3",
        "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/535.24 "
        "(KHTML, like Gecko) Chrome/19.0.1055.1 Safari/535.24",
        "Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/535.24 "
        "(KHTML, like Gecko) Chrome/19.0.1055.1 Safari/535.24"
]

代理操作：发送请求使用代理

request.meta['proxy'] = 'http://ip:port'

需要构建代理池

# 代理需要自己去获取，这里的已经无效
PROXY_http = [
    '153.180.102.104:80',
    '195.208.131.189:56055',
]
PROXY_https = [
    '120.83.49.90:9000',
    '95.189.112.214:35508',
]

注意点：不光在process_request方法中使用，在process_exception方法中也要使用

原因是：ip被封的时候访问某些网站，访问成功，但是返回了错误页面，有的直接是请求失败，针对这两种情况，应该分别设置中间件处理

拦截响应

篡改响应数据或者直接替换响应对象

拦截请求示例：

class MovieproDownloaderMiddleware(object):
    #拦截正常的请求，参数request就是拦截到的请求对象
    def process_request(self, request, spider):
        print('i am process_request()')
        #实现：将拦截到的请求尽可能多的设定成不同的请求载体身份标识
        request.headers['User-Agent'] = random.choice(user_agent_list)

        #代理操作
        if request.url.split(':')[0] == 'http':
            request.meta['proxy'] = 'http://'+random.choice(PROXY_http) #http://ip:port
        else:
            request.meta['proxy'] = 'https://' + random.choice(PROXY_https)  # http://ip:port

        return None
    #拦截响应：参数response就是拦截到的响应
    def process_response(self, request, response, spider):
        print('i am process_response()')
        return response
    #拦截发生异常的请求
    def process_exception(self, request, exception, spider):
        print('i am process_exception()')
        #拦截到异常的请求然后对其进行修正，然后重新进行请求发送
        # 代理操作
        if request.url.split(':')[0] == 'http':
            request.meta['proxy'] = 'http://' + random.choice(PROXY_http)  # http://ip:port
        else:
            request.meta['proxy'] = 'https://' + random.choice(PROXY_https)  # http://ip:port

        return request  #将修正之后的请求进行重新发送

selenium在scrapy中的使用

使用场景：有动态加载数据，此时访问首页url无法获取想要的数据，用到selenium进行获取

使用流程

1.实例化浏览器对象：写在爬虫类的构造方法中

bro = webdriver.Chrome(executable_path=r'C:\Users\oldboy-python\Desktop\爬虫+数据\tools\chromedriver.exe')

2.在中间件中执行浏览器自动化的操作

3.关闭浏览器：爬虫类中的closed(self,spider)关闭浏览器

def closed(self,spider):
    self.bro.quit()

拦截响应中间件的示例

1.先找到不满足要求的响应对象对应的请求对象

可以在爬虫类中定义容器，存储不满足要求响应对象的请求url

通过spider点方法进行获取，spider就是爬虫文件中爬虫类实例化的对象

2.通过HtmlResponse类重新发送请求，该请求对应的响应对象替换之前不满足要求的响应对象

from scrapy.http import HtmlResponse

new_response = HtmlResponse(url=request.url,body=page_text,encoding='utf-8',request=request)

def process_response(self, request, response, spider):

    #spider.five_model_urls:五个板块对应的url
    bro = spider.bro
    if request.url in spider.five_model_urls:
        bro.get(request.url)
        sleep(1)
        page_text = bro.page_source #包含了动态加载的新闻数据
        #如果if条件成立则该response就是五个板块对应的响应对象
        new_response = HtmlResponse(url=request.url,body=page_text,encoding='utf-8',request=request)
        return new_response


    return response

标签：like,Chrome,中间件,selenium,request,scrapy,AppleWebKit,Safari,KHTML
来源： https://www.cnblogs.com/Hedger-Lee/p/13074259.html