爬虫(22)scrapy登录与middlewares

第二十章 scrapy登录与middlewares

以前我们登录网站有两种方式：
一个是：直接携带cookie来请求页面
另一个：发送post请求携带数据进行模拟登录
当然selenium也能模拟登录（找到对应的input标签）。

1. scrapy携带cookie模拟登录

下面我们通过登录人人网案例来学习scrapy携带cookies登录方法。

1.1 创建项目

我们创建一个新的scrapy项目叫login

D:\work\爬虫\Day22>scrapy startproject login
New Scrapy project 'login', using template directory 'd:\python38\lib\site-packages\scrapy\templates\pro
ject', created in:
    D:\work\爬虫\Day22\login

You can start your first spider with:
    cd login
    scrapy genspider example example.com

D:\work\爬虫\Day22>

然后我们cd 到login

D:\work\爬虫\Day22>cd login

D:\work\爬虫\Day22\login>

我们先放一下。下面我们要操作的是携带cookie登录人人网。http://www.renren.com/
这是一个社交平台。下面我们创建spider项目：

D:\work\爬虫\Day22\login>scrapy genspider renren renren.com
Created spider 'renren' using template 'basic' in module:
  login.spiders.renren

D:\work\爬虫\Day22\login>

1.2 修改代码

现在我们可以打开查看我们刚刚创建的项目：

第一步我们先把start_url改了，改成详情页面的url

如果我们添加一个cookie值就能登录了，但是怎么添加呢？添加到什么地方呢？
response是已经拿到的响应结果，所以我们添加在parse这个方法的下面是没有意义的。

1.3 查看spider的源码

所以，我们一定要在请求地址的时候就携带cookie。下面我们分析一下spider的源码，Ctrl+点击spider

我们看到里面的代码：

"""
Base class for Scrapy spiders

See documentation in docs/topics/spiders.rst
"""
import logging
import warnings
from typing import Optional

from scrapy import signals
from scrapy.http import Request
from scrapy.utils.trackref import object_ref
from scrapy.utils.url import url_is_from_spider
from scrapy.utils.deprecate import method_is_overridden


class Spider(object_ref):
    """Base class for scrapy spiders. All spiders must inherit from this
    class.
    """

    name: Optional[str] = None
    custom_settings: Optional[dict] = None

    def __init__(self, name=None, **kwargs):
        if name is not None:
            self.name = name
        elif not getattr(self, 'name', None):
            raise ValueError(f"{type(self).__name__} must have a name")
        self.__dict__.update(kwargs)
        if not hasattr(self, 'start_urls'):
            self.start_urls = []

    @property
    def logger(self):
        logger = logging.getLogger(self.name)
        return logging.LoggerAdapter(logger, {'spider': self})

    def log(self, message, level=logging.DEBUG, **kw):
        """Log the given message at the given log level

        This helper wraps a log call to the logger within the spider, but you
        can use it directly (e.g. Spider.logger.info('msg')) or use any other
        Python logger too.
        """
        self.logger.log(level, message, **kw)

    @classmethod
    def from_crawler(cls, crawler, *args, **kwargs):
        spider = cls(*args, **kwargs)
        spider._set_crawler(crawler)
        return spider

    def _set_crawler(self, crawler):
        self.crawler = crawler
        self.settings = crawler.settings
        crawler.signals.connect(self.close, signals.spider_closed)

    def start_requests(self):
        cls = self.__class__
        if not self.start_urls and hasattr(self, 'start_url'):
            raise AttributeError(
                "Crawling could not start: 'start_urls' not found "
                "or empty (but found 'start_url' attribute instead, "
                "did you miss an 's'?)")
        if method_is_overridden(cls, Spider, 'make_requests_from_url'):
            warnings.warn(
                "Spider.make_requests_from_url method is deprecated; it "
                "won't be called in future Scrapy releases. Please "
                "override Spider.start_requests method instead "
                f"(see {cls.__module__}.{cls.__name__}).",
            )
            for url in self.start_urls:
                yield self.make_requests_from_url(url)
        else:
            for url in self.start_urls:
                yield Request(url, dont_filter=True)

    def make_requests_from_url(self, url):
        """ This method is deprecated. """
        warnings.warn(
            "Spider.make_requests_from_url method is deprecated: "
            "it will be removed and not be called by the default "
            "Spider.start_requests method in future Scrapy releases. "
            "Please override Spider.start_requests method instead."
        )
        return Request(url, dont_filter=True)

    def _parse(self, response, **kwargs):
        return self.parse(response, **kwargs)

    def parse(self, response, **kwargs):
        raise NotImplementedError(f'{self.__class__.__name__}.parse callback is not defined')

    @classmethod
    def update_settings(cls, settings):
        settings.setdict(cls.custom_settings or {}, priority='spider')

    @classmethod
    def handles_request(cls, request):
        return url_is_from_spider(request.url, cls)

    @staticmethod
    def close(spider, reason):
        closed = getattr(spider, 'closed', None)
        if callable(closed):
            return closed(reason)

    def __str__(self):
        return f"<{type(self).__name__} {self.name!r} at 0x{id(self):0x}>"

    __repr__ = __str__


# Top-level imports
from scrapy.spiders.crawl import CrawlSpider, Rule
from scrapy.spiders.feed import XMLFeedSpider, CSVFeedSpider
from scrapy.spiders.sitemap import SitemapSpider

1.4 重写start_requests(self)方法

我们看到里面有一个方法叫start_requests(self)

def start_requests(self):
        cls = self.__class__
        if not self.start_urls and hasattr(self, 'start_url'):
            raise AttributeError(
                "Crawling could not start: 'start_urls' not found "
                "or empty (but found 'start_url' attribute instead, "
                "did you miss an 's'?)")
        if method_is_overridden(cls, Spider, 'make_requests_from_url'):
            warnings.warn(
                "Spider.make_requests_from_url method is deprecated; it "
                "won't be called in future Scrapy releases. Please "
                "override Spider.start_requests method instead "