如何区分SOAP与REST请求？仅从请求内容判断XML服务类型

If you only have the XML payload to work with, here’s how to spot the difference:

1. SOAP Requests Have a Mandatory Envelope Wrapper #

This is the dead giveaway. Every valid SOAP XML request must have a root <Envelope> element (usually with a prefix like soap: or env:) that contains two child elements: an optional <Header> and a required <Body>.

Example SOAP XML:

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
  <soap:Header>
    <!-- Optional: Authentication tokens, transaction IDs, etc. -->
  </soap:Header>
  <soap:Body>
    <FetchUserById xmlns="http://yourcompany.com/api/users">
      <UserId>9876</UserId>
    </FetchUserById>
  </soap:Body>
</soap:Envelope>

Key markers:

• The <Envelope> uses a SOAP-specific namespace: either http://schemas.xmlsoap.org/soap/envelope/ (SOAP 1.1) or http://www.w3.org/2003/05/soap-envelope (SOAP 1.2).
• The actual request data lives inside the <Body>, wrapped in an operation-specific tag (like <FetchUserById> above).

2. REST XML Requests Have No Fixed Wrapper #

REST XML payloads are all about the data—no required envelope, header, or body layers. The root element is directly tied to the resource being manipulated.

Example REST XML for updating a user:

<User>
  <Id>9876</Id>
  <FirstName>Updated</FirstName>
  <LastName>Name</LastName>
  <Email>updated.name@example.com</Email>
</User>

Key markers:

• No SOAP-specific namespaces. Any namespaces present will be tied to your application’s domain, not official SOAP specs.
• The XML directly represents the resource/data being sent. The action (update, create, etc.) is determined by the HTTP method used with the request, not something embedded in the XML itself.

3. Error Handling Structure #

If you’re looking at an error response:

• SOAP errors are wrapped in a <soap:Fault> element inside the <soap:Body>, with fixed fields like faultcode and faultstring.
• REST XML errors are custom—they might use elements like <Error> or <Status> with app-specific fields, no standardized structure.

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