爬取伯乐在线文章（四）将爬取结果保存到MySQL

Item Pipeline

当Item在Spider中被收集之后，它将会被传递到Item Pipeline，这些Item Pipeline组件按定义的顺序处理Item。

每个Item Pipeline都是实现了简单方法的Python类，比如决定此Item是丢弃而存储。以下是item pipeline的一些典型应用：

• 验证爬取的数据(检查item包含某些字段，比如说name字段)
• 查重(并丢弃)
• 将爬取结果保存到文件或者数据库中

编写item

在items.py中进行编写

class JobBoleArticleItem(scrapy.Item):
    title = scrapy.Field()
    create_date = scrapy.Field()
    praise_num = scrapy.Field()
    collect_num = scrapy.Field()
    comment_num = scrapy.Field()
    front_image_url = scrapy.Field()

编写之后在提取文章逻辑里面进行实例化

    def parse_detail(self,response):
        print("目前爬取的URL是："+response.url)
        #提取文章的具体逻辑
        article_item = JobBoleArticleItem()
        front_image_url = response.meta.get("front_image_url", "")
        #  获取文章标题
        title = response.css('.entry-header h1::text').extract()[0]
        #  获取发布日期
        create_date = response.css('.entry-meta .entry-meta-hide-on-mobile::text').extract()[0].strip().replace("·", "")
        #  获取点赞数
        praise_num = response.css('.vote-post-up h10::text').extract()[0]
        #  获取收藏数
        collect_num = response.css('.post-adds .bookmark-btn::text').extract()[0].split(" ")[1]
        collect_match_re = re.match(r'.*?(\d+).*', collect_num)
        if collect_match_re:
            collect_num = int(collect_match_re.group(1))
        else:
            collect_num = 0
        #  获取评论数
        comment_num = response.css('.post-adds .hide-on-480::text').extract()[0]
        comment_match_re = re.match(r'.*?(\d+).*', comment_num)
        if comment_match_re:
            comment_num = int(comment_match_re.group(1))
        else:
            comment_num = 0

        content = response.css('div.entry').extract()[0]

        article_item["title"] = title
        article_item["create_date"] =create_date
        article_item["praise_num"] = praise_num
        article_item["collect_num"] = collect_num
        article_item["comment_num"] = comment_num
        article_item["front_image_url"] = front_image_url

        yield article_item

最后调用yield article_item之后，article_item会传递到pipelines.py里面

编写pipelines

在pipelines.py文件中模板已经写好，但是如果要使之生效，需要修改settings.py文件，将ITEM_PIPELINES的注释去掉

在pipelines.py里面打断点进行调试，看article_item是否能传递尽来

如何将图片保存到本地

继续修改item，scrapy提供了一些方法，方便快速开发，修改settings.py

ITEM_PIPELINES = {
    'EnterpriseSpider.pipelines.EnterprisespiderPipeline': 300,
    'scrapy.pipelines.images.ImagesPipeline': 1,
}
IMAGES_URLS_FIELD = "front_image_url"
project_dir = os.path.abspath(os.path.dirname(__file__))
IMAGES_STORE = os.path.join(project_dir, "images")

'scrapy.pipelines.images.ImagesPipeline': 1-------设置scrapy自带的普票保存方法，后面设置数字是流经管道的顺序，数字小的先流经

IMAGES_URLS_FIELD = "front_image_url"------从item中提取图片的URL，前面的IMAGES_URLS_FIELD是固定写法

project_dir = os.path.abspath(os.path.dirname(__file__))：获取当前项目的路径

IMAGES_STORE = os.path.join(project_dir, "images")：设置图片存储的路径

此时运行我们的main看是否能将图片保存

报错，没有PIL这个模块，这个是与图片文件相关的库，我们没有按照，所以报错，在虚拟环境中安装PIL模块

(scrapyenv) E:\Python\Envs>pip install -i https://pypi.douban.com/simple pillow

安装之后重新运行程序，此时又报另一个错误

这个因为item传递到pipline的时候，下面的front_image_url 会被当做数组处理，但是我们在业务逻辑处理时候只是把他当做一个值进行处理

IMAGES_URLS_FIELD = "front_image_url"

修改业务处理逻辑

        article_item["title"] = title
        article_item["create_date"] =create_date
        article_item["praise_num"] = praise_num
        article_item["collect_num"] = collect_num
        article_item["comment_num"] = comment_num
        article_item["front_image_url"] = [front_image_url]

        yield article_item

修改完之后在运行程序，此时爬取的图片成功保存到images文件夹下面

既然图片已经保存到本地了，那么是否可以提取出路径，是否能把item里面的front_image_url与本地路径绑定在一起，此时我们需要定义一个自己pipeline，重载ImagesPipeline 中的item_completed

方法。

class ArticleImagePipeline(ImagesPipeline):
    def item_completed(self, results, item, info):
        pass

此时在修改settings.py文件，设置问我们自定义的图片处理pipeline

ITEM_PIPELINES = {
    'EnterpriseSpider.pipelines.EnterprisespiderPipeline': 300,
   # 'scrapy.pipelines.images.ImagesPipeline': 1,
    'EnterpriseSpider.pipelines.ArticleImagePipeline': 1,
}

打断点进行调试

重写item_completed方法

class ArticleImagePipeline(ImagesPipeline):
    def item_completed(self, results, item, info):
        for ok, value in results:
            image_file_path = results["path"]
        item["front_image_url"] = image_file_path
        return item

保存到JSON

class JsonWithEncodingPipeline(object):
    def __init__(self):
        self.file = codecs.open('article.json', 'w', encoding='utf-8')

    def process_item(self,item,spider):
        lines = json.dumps(dict(item), ensure_ascii=False) + "\n"
        self.file.write(lines)
        return item

    def spider_closed(self,spider):
        self.file.close()

保存到MySQL

同步保存

class MysqlPipeline(object):
    def __init__(self):
        self.conn = MySQLdb.connect('127.0.0.1', 'root', '', 'article', charset='utf8', use_unicode=True)
        self.cursor = self.conn.cursor()

    def process_item(self,item,spider):
        insert_sql = '''
        insert into jobbole(title,create_date,front_image_url,praise_num,collect_num,comment_num,url,url_object_id)
        VALUES (%s, %s, %s, %s, %s, %s, %s, %s)
        '''

        self.cursor.execute(insert_sql, (item['title'], item['create_date'], item["front_image_url"],
                                         item["praise_num"], item["collect_num"], item["comment_num"],
                                         item["url"], item["url_object_id"]))
        self.conn.commit()

异步保存

class MysqlTwistedPipeline(object):

    def __init__(self, dbpool):
        self.dbpool = dbpool

    @classmethod
    def from_settings(cls, settings):
        dbparams = dict(
            host=settings['MYSQL_HOST'],
            db=settings['MYSQL_DBNAME'],
            user=settings['MYSQL_USER'],
            password=settings['MYSQL_PASSWORD'],
            charset='utf8',
            cursorclass=MySQLdb.cursors.DictCursor,
            use_unicode=True,
        )
        dbpool = adbapi.ConnectionPool("MySQLdb", **dbparams)
        return cls(dbpool)

    def process_item(self,item,spider):
        #使用twisted将mysql插入变成异步插入
        query = self.dbpool.runInteraction(self.db_insert, item)
        query.addErrback(self.handler_error, item, spider)

    def handler_error(self,failuer,item,spider):
        #处理异步插入的异常
        print(failuer)

    def db_insert(self,cursor,item):
        insert_sql = '''
                    insert into jobbole(title,create_date,front_image_url,praise_num,collect_num,comment_num,url,url_object_id)
                    VALUES (%s, %s, %s, %s, %s, %s, %s, %s)
                '''

        cursor.execute(insert_sql, (item['title'], item['create_date'], item["front_image_url"],
                                         item["praise_num"], item["collect_num"], item["comment_num"],
                                         item["url"], item["url_object_id"]))