python爬蟲實現(xiàn)POST request payload形式的請求

更新時間：2020年04月30日 15:00:01 作者：Kosmoo

這篇文章主要介紹了python爬蟲實現(xiàn)POST request payload形式的請求，具有很好的參考價值，希望對大家有所幫助。一起跟隨小編過來看看吧

1. 背景

最近在爬取某個站點時，發(fā)現(xiàn)在POST數(shù)據(jù)時，使用的數(shù)據(jù)格式是request payload，有別于之前常見的 POST數(shù)據(jù)格式（Form data）。而使用Form data數(shù)據(jù)的提交方式時，無法提交成功。

1.1. Http請求中Form Data 和 Request Payload的區(qū)別

AJAX Post請求中常用的兩種傳參數(shù)的形式：form data 和 request payload

1.1.1. Form data

get請求的時候，我們的參數(shù)直接反映在url里面，形式為key1=value1&key2=value2形式，比如：

http://news.baidu.com/ns?word=NBA&tn=news&from=news&cl=2&rn=20&ct=1

而如果是post請求，那么表單參數(shù)是在請求體中，也是以key1=value1&key2=value2的形式在請求體中。通過chrome的開發(fā)者工具可以看到，如下：

RequestURL:http://127.0.0.1:8080/test/test.do
Request Method:POST
Status Code:200 OK

Request Headers
Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Encoding:gzip,deflate,sdch
Accept-Language:zh-CN,zh;q=0.8,en;q=0.6
AlexaToolbar-ALX_NS_PH:AlexaToolbar/alxg-3.2
Cache-Control:max-age=0
Connection:keep-alive
Content-Length:25
Content-Type:application/x-www-form-urlencoded
Cookie:JSESSIONID=74AC93F9F572980B6FC10474CD8EDD8D
Host:127.0.0.1:8080
Origin:http://127.0.0.1:8080
Referer:http://127.0.0.1:8080/test/index.jsp
User-Agent:Mozilla/5.0 (Windows NT 6.1)AppleWebKit/537.36 (KHTML, like Gecko) Chrome/33.0.1750.149 Safari/537.36

Form Data
name:mikan
address:street

Response Headers
Content-Length:2
Date:Sun, 11 May 2014 11:05:33 GMT
Server:Apache-Coyote/1.1

這里要注意post請求的Content-Type為application/x-www-form-urlencoded（默認的），參數(shù)是在請求體中，即上面請求中的Form Data。

前端代碼：提交數(shù)據(jù)

xhr.setRequestHeader("Content-type","application/x-www-form-urlencoded");

xhr.send("name=foo&value=bar");

后端代碼：接收提交的數(shù)據(jù)。在servlet中，可以通過request.getParameter(name)的形式來獲取表單參數(shù)。

/**
 * 獲取httpRequest的參數(shù)
 * 
 * @param request
 * @param name
 * @return
 */
protected String getParameterValue(HttpServletRequest request, String name) {
 return StringUtils.trimToEmpty(request.getParameter(name));
}

1.1.2. Request payload

如果使用原生AJAX POST請求的話，那么請求在chrome的開發(fā)者工具的表現(xiàn)如下，主要是參數(shù)在

Remote Address:192.168.234.240:80
Request URL:http://tuanbeta3.XXX.com/qimage/upload.htm
Request Method:POST
Status Code:200 OK

Request Headers
Accept:application/json, text/javascript, */*; q=0.01
Accept-Encoding:gzip,deflate,sdch
Accept-Language:zh-CN,zh;q=0.8,en;q=0.6
Connection:keep-alive
Content-Length:151
Content-Type:application/json;charset=UTF-8
Cookie:JSESSIONID=E08388788943A651924CA0A10C7ACAD0
Host:tuanbeta3.XXX.com
Origin:http://tuanbeta3.XXX.com
Referer:http://tuanbeta3.XXX.com/qimage/customerlist.htm?menu=19
User-Agent:Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/35.0.1916.114 Safari/537.36
X-Requested-With:XMLHttpRequest

Request Payload
[{widthEncode:NNNcaXN, heightEncode:NNNN5NN, displayUrl:201409/03/66I5P266rtT86oKq6,…}]

Response Headers
Connection:keep-alive
Content-Encoding:gzip
Content-Type:application/json;charset=UTF-8
Date:Thu, 04 Sep 2014 06:49:44 GMT
Server:nginx/1.4.7
Transfer-Encoding:chunked
Vary:Accept-Encoding

注意請求的Content-Type是application/json;charset=UTF-8，而請求表單的參數(shù)在Request Payload中。

后端代碼：獲取數(shù)據(jù)（這里使用org.apache.commons.io.）：

/**
 * 從 request 獲取 payload 數(shù)據(jù)
 *
 * @param request
 * @return
 * @throws IOException
 */
private String getRequestPayload(HttpServletRequest request) throws IOException {
 return IOUtils.toString(request.getReader());
}

1.1.3. 二者區(qū)別

如果一個請求的Content-Type設(shè)置為application/x-www-form-urlencoded，那么這個Post請求會被認為是Http Post表單請求，那么請求主體將以一個標準的鍵值對和&的querystring形式出現(xiàn)。這種方式是HTML表單的默認設(shè)置，所以在過去這種方式更加常見。

其他形式的POST請求，是放到 Request payload 中（現(xiàn)在是為了方便閱讀，使用了Json這樣的數(shù)據(jù)格式），請求的Content-Type設(shè)置為application/json;charset=UTF-8或者不指定。

2. 環(huán)境

python 3.6.1

系統(tǒng)：win7

IDE：pycharm

requests 2.14.2

scrapy 1.4.0

3. 使用requests模塊post payload請求

import json
import requests
import datetime

postUrl = 'https://sellercentral.amazon.com/fba/profitabilitycalculator/getafnfee?profitcalcToken=en2kXFaY81m513NydhTZ9sdb6hoj3D'
# payloadData數(shù)據(jù)
payloadData = {
 'afnPriceStr': 10,
 'currency':'USD',
 'productInfoMapping': {
  'asin': 'B072JW3Z6L',
  'dimensionUnit': 'inches',
 }
}
# 請求頭設(shè)置
payloadHeader = {
 'Host': 'sellercentral.amazon.com',
 'Content-Type': 'application/json',
}
# 下載超時
timeOut = 25
# 代理
proxy = "183.12.50.118:8080"
proxies = {
 "http": proxy,
 "https": proxy,
}
r = requests.post(postUrl, data=json.dumps(payloadData), headers=payloadHeader)
dumpJsonData = json.dumps(payloadData)
print(f"dumpJsonData = {dumpJsonData}")
res = requests.post(postUrl, data=dumpJsonData, headers=payloadHeader, timeout=timeOut, proxies=proxies, allow_redirects=True)
# 下面這種直接填充json參數(shù)的方式也OK
# res = requests.post(postUrl, json=payloadData, headers=header)
print(f"responseTime = {datetime.datetime.now()}, statusCode = {res.status_code}, res text = {res.text}")

4. 在scrapy中post payload請求

這兒有個壞消息，那就是scrapy目前還不支持payload這種request請求。而且scrapy對formdata的請求也有很嚴格的要求，具體可以參考這篇文章：http://www.dbjr.com.cn/article/185824.htm

4.1. 分析scrapy源碼

參考注解

# 文件：E:\Miniconda\Lib\site-packages\scrapy\http\request\form.py
class FormRequest(Request):

 def __init__(self, *args, **kwargs):
  formdata = kwargs.pop('formdata', None)
  if formdata and kwargs.get('method') is None:
   kwargs['method'] = 'POST'

  super(FormRequest, self).__init__(*args, **kwargs)

  if formdata:
   items = formdata.items() if isinstance(formdata, dict) else formdata
   querystr = _urlencode(items, self.encoding)
   # 這兒寫死了，當提交數(shù)據(jù)時，設(shè)置好Content-Type，也就是form data類型
   # 就算改寫這兒，后面也沒有對 json數(shù)據(jù)解析的處理
   if self.method == 'POST':
    self.headers.setdefault(b'Content-Type', b'application/x-www-form-urlencoded')
    self._set_body(querystr)
   else:
    self._set_url(self.url + ('&' if '?' in self.url else '?') + querystr)

4.2. 思路：在scrapy中嵌入requests模塊

分析請求

返回的查詢結(jié)果

第一步：在爬蟲中構(gòu)造請求，把所有的參數(shù)以及必要信息帶進去。

返回的查詢結(jié)果

第一步：在爬蟲中構(gòu)造請求，把所有的參數(shù)以及必要信息帶進去。

# 文件 mySpider.py中

payloadData = {}
payloadData['afnPriceStr'] = 0
payloadData['currency'] = asinInfo['currencyCodeHidden']
payloadData['futureFeeDate'] = asinInfo['futureFeeDateHidden']
payloadData['hasFutureFee'] = False
payloadData['hasTaxPage'] = True
payloadData['marketPlaceId'] = asinInfo['marketplaceIdHidden']
payloadData['mfnPriceStr'] = 0
payloadData['mfnShippingPriceStr'] = 0
payloadData['productInfoMapping'] = {}
payloadData['productInfoMapping']['asin'] = dataFieldJson['asin']
payloadData['productInfoMapping']['binding'] = dataFieldJson['binding']
payloadData['productInfoMapping']['dimensionUnit'] = dataFieldJson['dimensionUnit']
payloadData['productInfoMapping']['dimensionUnitString'] = dataFieldJson['dimensionUnitString']
payloadData['productInfoMapping']['encryptedMarketplaceId'] = dataFieldJson['encryptedMarketplaceId']
payloadData['productInfoMapping']['gl'] = dataFieldJson['gl']
payloadData['productInfoMapping']['height'] = dataFieldJson['height']
payloadData['productInfoMapping']['imageUrl'] = dataFieldJson['imageUrl']
payloadData['productInfoMapping']['isAsinLimits'] = dataFieldJson['isAsinLimits']
payloadData['productInfoMapping']['isWhiteGloveRequired'] = dataFieldJson['isWhiteGloveRequired']
payloadData['productInfoMapping']['length'] = dataFieldJson['length']
payloadData['productInfoMapping']['link'] = dataFieldJson['link']
payloadData['productInfoMapping']['originalUrl'] = dataFieldJson['originalUrl']
payloadData['productInfoMapping']['productGroup'] = dataFieldJson['productGroup']
payloadData['productInfoMapping']['subCategory'] = dataFieldJson['subCategory']
payloadData['productInfoMapping']['thumbStringUrl'] = dataFieldJson['thumbStringUrl']
payloadData['productInfoMapping']['title'] = dataFieldJson['title']
payloadData['productInfoMapping']['weight'] = dataFieldJson['weight']
payloadData['productInfoMapping']['weightUnit'] = dataFieldJson['weightUnit']
payloadData['productInfoMapping']['weightUnitString'] = dataFieldJson['weightUnitString']
payloadData['productInfoMapping']['width'] = dataFieldJson['width']
# https://sellercentral.amazon.com/fba/profitabilitycalculator/getafnfee?profitcalcToken=en2kXFaY81m513NydhTZ9sdb6hoj3D
postUrl = f"https://sellercentral.amazon.com/fba/profitabilitycalculator/getafnfee?profitcalcToken={asinInfo['tokenValue']}"
payloadHeader = {
 'Host': 'sellercentral.amazon.com',
 'Content-Type': 'application/json',
}
# scrapy源碼：self.headers.setdefault(b'Content-Type', b'application/x-www-form-urlencoded')
print(f"payloadData = {payloadData}")
# 這個request并不真正用來調(diào)度，去發(fā)出請求，因為這種方式構(gòu)造方式，是無法提交成功的，會返回404錯誤
# 這樣構(gòu)造主要是把查詢參數(shù)提交出去，在下載中間件部分用request模塊下載，用 “payloadFlag” 標記這種request
yield Request(url = postUrl,
    headers = payloadHeader,
    meta = {'payloadFlag': True, 'payloadData': payloadData, 'headers': payloadHeader, 'asinInfo': asinInfo},
    callback = self.parseAsinSearchFinallyRes,
    errback = self.error,
    dont_filter = True
    )

第二步：在中間件中，用requests模塊處理這個請求

# 文件：middlewares.py

class PayLoadRequestMiddleware:
 def process_request(self, request, spider):
  # 如果有的請求是帶有payload請求的，在這個里面處理掉
  if request.meta.get('payloadFlag', False):
   print(f"PayLoadRequestMiddleware enter")
   postUrl = request.url
   headers = request.meta.get('headers', {})
   payloadData = request.meta.get('payloadData', {})
   proxy = request.meta['proxy']
   proxies = {
    "http": proxy,
    "https": proxy,
   }
   timeOut = request.meta.get('download_timeout', 25)
   allow_redirects = request.meta.get('dont_redirect', False)
   dumpJsonData = json.dumps(payloadData)
   print(f"dumpJsonData = {dumpJsonData}")
   # 發(fā)現(xiàn)這個居然是個同步 阻塞的過程，太過影響速度了
   res = requests.post(postUrl, data=dumpJsonData, headers=headers, timeout=timeOut, proxies=proxies, allow_redirects=allow_redirects)
   # res = requests.post(postUrl, json=payloadData, headers=header)
   print(f"responseTime = {datetime.datetime.now()}, res text = {res.text}, statusCode = {res.status_code}")
   if res.status_code > 199 and res.status_code < 300:
    # 返回Response，就進入callback函數(shù)處理，不會再去下載這個請求
    return HtmlResponse(url=request.url,
         body=res.content,
         request=request,
         # 最好根據(jù)網(wǎng)頁的具體編碼而定
         encoding='utf-8',
         status=200)
   else:
    print(f"request mode getting page error, Exception = {e}")
    return HtmlResponse(url=request.url, status=500, request=request)

4.3. 遺留下的問題

scrapy之所以強大，就是因為并發(fā)度高。大家都知道，由于Python GIL的原因，導致python無法通過多線程來提高性能。但是至少可以做到下載與解析同步的過程，在下載空檔的時候，進行數(shù)據(jù)的解析，調(diào)度等等，這都歸功于scrapy采用的異步結(jié)構(gòu)。

但是，我們在中間件中使用requests模塊進行網(wǎng)頁下載，因為這是個同步過程，所以會阻塞在這個地方，拉低了整個爬蟲的效率。

所以，需要根據(jù)項目具體的情況，來決定合適的方案。當然這里又涉及到一個新的話題，就是scrapy提供的兩種爬取模式：深度優(yōu)先模式和廣度優(yōu)先模式。如何盡可能最大限度的利用scrapy的并發(fā)？在環(huán)境不穩(wěn)定的情形下如何保證盡可能穩(wěn)定的拿到數(shù)據(jù)？

深度優(yōu)先模式和廣度優(yōu)先模式是在settings中設(shè)置的。

# 文件： settings.py

# DEPTH_PRIORITY（默認值為0）設(shè)置為一個正值后，Scrapy的調(diào)度器的隊列就會從LIFO變成FIFO，因此抓取規(guī)則就由DFO（深度優(yōu)先）變成了BFO（廣度優(yōu)先）
DEPTH_PRIORITY = 1, # 廣度優(yōu)先（肯呢個會累積大量的request，累計占有大量的內(nèi)存，最終數(shù)據(jù)也在最后一批爬?。?

深度優(yōu)先：DEPTH_PRIORITY = 0