使用变量设置WebKitFormBoundary导致POST请求失效求助

我有一段能成功发送POST请求的Python代码，返回响应تم تسجيل الطلب بنجاح（意为“注册成功”）。为简化代码，尝试用变量定义WebKitFormBoundary的值，但修改后的代码无法正常发起请求，请问该如何解决？

原成功代码 #

import requests

cookies = {'BNES_JSESSIONID': 'R2aVMfNrT78PyhSgyqW6Kj7BlBMOR7cQqB+Tq7wGQl34xSno1KKqpymu/ZLhny2lshfxmOnZiFy8Zbvw+vcSPCPOAALQXhOdFcYX61dU7WDszMVLkwHKehvnHfmubbwQG5BhwWAjqWJlKz22mi985kyPwyYEwx8y'}
headers = {'Content-Type': 'multipart/form-data; boundary=----WebKitFormBoundaryB6r6VIYgOSHWqj5I'}
data = '------WebKitFormBoundaryB6r6VIYgOSHWqj5I\r\nContent-Disposition: form-data; name="selectAser"\r\n\r\n211053300\r\n------WebKitFormBoundaryB6r6VIYgOSHWqj5I\r\nContent-Disposition: form-data; name="phoneNo"\r\n\r\n55075052\r\n------WebKitFormBoundaryB6r6VIYgOSHWqj5I\r\nContent-Disposition: form-data; name="selectAsed"\r\n\r\n120987470-1\r\n------WebKitFormBoundaryB6r6VIYgOSHWqj5I\r\nContent-Disposition: form-data; name="comReg"\r\n\r\n\r\n------WebKitFormBoundaryB6r6VIYgOSHWqj5I\r\nContent-Disposition: form-data; name="bankType"\r\n\r\n1850\r\n------WebKitFormBoundaryB6r6VIYgOSHWqj5I\r\nContent-Disposition: form-data; name="attachments"; filename=""\r\nContent-Type: application/octet-stream\r\n\r\n\r\n------WebKitFormBoundaryB6r6VIYgOSHWqj5I\r\nContent-Disposition: form-data; name="searchType"\r\n\r\n0745\r\n------WebKitFormBoundaryB6r6VIYgOSHWqj5I--\r\n'

response = requests.post('https://eservices.gov./', cookies=cookies, headers=headers, data=data)
print(response.text)

修改后失效的代码 #

import requests

def post_with_custom_boundary(c_boundary):
    url = 'https://eservices.gov./'
    cookies = {'BNES_JSESSIONID': 'FBVxGgtjjJhDGmcnG/XOglUeuJlG/mwpJH9+ICQw/bL3/2Y383HWR4f+WzRXsJBG5jHf33qCsgMBOHLeTKxJRBwlkrkKE1tGbdywVgdikWhC4VcCUd1yIIYJBFm4m/60lfkGqvgk+UfaMbPKe3CUVRvsTaMCLn+A'}
    headers = {'Content-Type': f'multipart/form-data; boundary={c_boundary}'}

    data = f'{c_boundary}\r\nContent-Disposition: form-data; name="selectAser"\r\n\r\n211053300\r\n{c_boundary}\r\nContent-Disposition: form-data; name="phoneNo"\r\n\r\n55075052\r\n{c_boundary}\r\nContent-Disposition: form-data; name="selectAsed"\r\n\r\n120987470-1\r\n{c_boundary}\r\nContent-Disposition: form-data; name="comReg"\r\n\r\n\r\n{c_boundary}\r\nContent-Disposition: form-data; name="bankType"\r\n\r\n1850\r\n{c_boundary}\r\nContent-Disposition: form-data; name="attachments"; filename=""\r\nContent-Type: application/octet-stream\r\n\r\n\r\n{c_boundary}\r\nContent-Disposition: form-data; name="searchType"\r\n\r\n0745\r\n{c_boundary}--\r\n'

    response = requests.post(url, cookies=cookies, headers=headers, data=data)
    print(response.text)

c_boundary = '------WebKitFormBoundaryg3LDfuaso7lfkkvj'
post_with_custom_boundary(c_boundary)

问题原因 #

对比两段代码的boundary格式：

• 原代码中，headers里的boundary值是4个短横线开头：----WebKitFormBoundaryB6r6VIYgOSHWqj5I
• 而data里的每个分隔符是8个短横线开头：------WebKitFormBoundaryB6r6VIYgOSHWqj5I

修改后的代码把c_boundary定义为8个短横线开头，直接放到headers里，导致服务器收到的Content-Type中的boundary值和请求体里的分隔符不匹配，无法正确解析multipart数据。

解决方案 #

需要保证headers中的boundary值是请求体分隔符去掉前4个短横线的版本，有两种实现方式：

方式1：拆分boundary前缀和主体

import requests

def post_with_custom_boundary(boundary_body):
    url = 'https://eservices.gov./'
    cookies = {'BNES_JSESSIONID': 'FBVxGgtjjJhDGmcnG/XOglUeuJlG/mwpJH9+ICQw/bL3/2Y383HWR4f+WzRXsJBG5jHf33qCsgMBOHLeTKxJRBwlkrkKE1tGbdywVgdikWhC4VcCUd1yIIYJBFm4m/60lfkGqvgk+UfaMbPKe3CUVRvsTaMCLn+A'}
    # header里用4个短横线+主体
    headers = {'Content-Type': f'multipart/form-data; boundary=----{boundary_body}'}
    # 请求体里用8个短横线+主体
    boundary = f'------{boundary_body}'

    data = f'{boundary}\r\nContent-Disposition: form-data; name="selectAser"\r\n\r\n211053300\r\n{boundary}\r\nContent-Disposition: form-data; name="phoneNo"\r\n\r\n55075052\r\n{boundary}\r\nContent-Disposition: form-data; name="selectAsed"\r\n\r\n120987470-1\r\n{boundary}\r\nContent-Disposition: form-data; name="comReg"\r\n\r\n\r\n{boundary}\r\nContent-Disposition: form-data; name="bankType"\r\n\r\n1850\r\n{boundary}\r\nContent-Disposition: form-data; name="attachments"; filename=""\r\nContent-Type: application/octet-stream\r\n\r\n\r\n{boundary}\r\nContent-Disposition: form-data; name="searchType"\r\n\r\n0745\r\n{boundary}--\r\n'

    response = requests.post(url, cookies=cookies, headers=headers, data=data)
    print(response.text)

# 只传boundary主体部分
boundary_body = 'WebKitFormBoundaryg3LDfuaso7lfkkvj'
post_with_custom_boundary(boundary_body)

方式2：对传入的c_boundary做截取

如果想保留原变量定义方式，直接截取前4个短横线后的部分放到header里：

import requests

def post_with_custom_boundary(c_boundary):
    url = 'https://eservices.gov./'
    cookies = {'BNES_JSESSIONID': 'FBVxGgtjjJhDGmcnG/XOglUeuJlG/mwpJH9+ICQw/bL3/2Y383HWR4f+WzRXsJBG5jHf33qCsgMBOHLeTKxJRBwlkrkKE1tGbdywVgdikWhC4VcCUd1yIIYJBFm4m/60lfkGqvgk+UfaMbPKe3CUVRvsTaMCLn+A'}
    # 截取c_boundary去掉前4个短横线的部分
    headers = {'Content-Type': f'multipart/form-data; boundary={c_boundary[4:]}'}

    data = f'{c_boundary}\r\nContent-Disposition: form-data; name="selectAser"\r\n\r\n211053300\r\n{c_boundary}\r\nContent-Disposition: form-data; name="phoneNo"\r\n\r\n55075052\r\n{c_boundary}\r\nContent-Disposition: form-data; name="selectAsed"\r\n\r\n120987470-1\r\n{c_boundary}\r\nContent-Disposition: form-data; name="comReg"\r\n\r\n\r\n{c_boundary}\r\nContent-Disposition: form-data; name="bankType"\r\n\r\n1850\r\n{c_boundary}\r\nContent-Disposition: form-data; name="attachments"; filename=""\r\nContent-Type: application/octet-stream\r\n\r\n\r\n{c_boundary}\r\nContent-Disposition: form-data; name="searchType"\r\n\r\n0745\r\n{c_boundary}--\r\n'

    response = requests.post(url, cookies=cookies, headers=headers, data=data)
    print(response.text)

c_boundary = '------WebKitFormBoundaryg3LDfuaso7lfkkvj'
post_with_custom_boundary(c_boundary)

额外建议 #

其实requests库本身支持自动处理multipart/form-data请求，不需要手动拼接boundary和请求体，用files参数可以更简洁，避免手动拼接出错：

import requests

url = 'https://eservices.gov./'
cookies = {'BNES_JSESSIONID': 'FBVxGgtjjJhDGmcnG/XOglUeuJlG/mwpJH9+ICQw/bL3/2Y383HWR4f+WzRXsJBG5jHf33qCsgMBOHLeTKxJRBwlkrkKE1tGbdywVgdikWhC4VcCUd1yIIYJBFm4m/60lfkGqvgk+UfaMbPKe3CUVRvsTaMCLn+A'}

# 构造表单数据
form_data = {
    'selectAser': ('', '211053300'),
    'phoneNo': ('', '55075052'),
    'selectAsed': ('', '120987470-1'),
    'comReg': ('', ''),
    'bankType': ('', '1850'),
    'attachments': ('', '', 'application/octet-stream'),
    'searchType': ('', '0745')
}

response = requests.post(url, cookies=cookies, files=form_data)
print(response.text)

这种方式requests会自动生成正确的boundary，无需手动处理，代码更简洁可靠。

内容的提问来源于stack exchange，提问作者YasserKhalil