使用Ruby Net::HTTP调用multipart/form-data API时出现无边界错误

问题原因 #

你遇到的错误是因为服务器未接收到multipart请求的边界标识。Ruby标准库的Net::HTTP#set_form方法在手动传入字符串'multipart/form-data'作为content type时，不会自动生成并添加边界参数到请求头，导致服务器无法解析请求体。

修复方案 #

1. 改用:multipart符号自动生成边界

将原代码中的：

request.set_form form_data, 'multipart/form-data'

替换为：

request.set_form form_data, :multipart

当传入:multipart时，Net::HTTP会自动生成随机边界，并将Content-Type请求头设置为multipart/form-data; boundary=xxxxxx，服务器就能正确识别并解析请求。

2. 优化表单数据格式（可选但推荐）

• 为email_data字段指定application/json的content type，确保服务器正确解析JSON内容
• 以二进制模式读取文件，避免编码问题
• 显式指定文件名，符合HTTP规范

修改后的form_data：

form_data = [
  [
    'email_data',
    '{"message":"Test\tMessage","type":"mobi","priority":"LOW","email":{"to_email_ids":["awadesh@temp.com"],"cc_email_ids":[],"bcc_email_ids":[],"from_email_id":"automation@temp.com","subject":"subject - test email","attachment":[]}}',
    { content_type: 'application/json' }
  ],
  [
    'attachment',
    File.open('/Users/dummy/Desktop/Screenshot 2022-11-07 at 10.45.11 AM.png', 'rb'),
    { filename: 'Screenshot 2022-11-07 at 10.45.11 AM.png' }
  ]
]

完整修复后的代码

require "uri"
require "net/http"

url = URI("[base_url]/rest/v1/companies/11/notifications/email-with-attachment?content_type=static")

https = Net::HTTP.new(url.host, url.port)
https.use_ssl = true

request = Net::HTTP::Post.new(url)
request["client"] = "mobi"
form_data = [
  [
    'email_data',
    '{"message":"Test\tMessage","type":"mobi","priority":"LOW","email":{"to_email_ids":["awadesh@temp.com"],"cc_email_ids":[],"bcc_email_ids":[],"from_email_id":"automation@temp.com","subject":"subject - test email","attachment":[]}}',
    { content_type: 'application/json' }
  ],
  [
    'attachment',
    File.open('/Users/dummy/Desktop/Screenshot 2022-11-07 at 10.45.11 AM.png', 'rb'),
    { filename: 'Screenshot 2022-11-07 at 10.45.11 AM.png' }
  ]
]
request.set_form form_data, :multipart

response = https.request(request)
puts response.read_body

验证逻辑 #

修改后，Net::HTTP会自动处理边界生成和请求头设置，请求格式会与curl的有效请求一致，服务器就能正常解析multipart数据。

内容的提问来源于stack exchange，提问作者Awadesh