Format SOAP XML Messages — Envelope, Header, and Body

Formatting SOAP XML

SOAP (Simple Object Access Protocol) messages are XML documents with a specific structure: an Envelope element containing optional Header and required Body elements. Formatting SOAP XML makes these deeply nested, namespace-heavy messages readable.

SOAP Envelope Structure

<soap:Envelope
  xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"
  xmlns:ws="http://example.com/webservice">
  <soap:Header>
    <ws:AuthToken>abc123</ws:AuthToken>
  </soap:Header>
  <soap:Body>
    <ws:GetUserRequest>
      <ws:UserId>42</ws:UserId>
    </ws:GetUserRequest>
  </soap:Body>
</soap:Envelope>

Namespace Prefixes

SOAP messages heavily use XML namespaces. Each prefix (soap:, ws:, xsi:, etc.) is bound to a URI via xmlns declarations. A good formatter preserves these declarations and keeps them aligned for readability.

Common Namespace URIs

• http://schemas.xmlsoap.org/soap/envelope/ — SOAP 1.1
• http://www.w3.org/2003/05/soap-envelope — SOAP 1.2
• http://www.w3.org/2001/XMLSchema-instance — XML Schema Instance
• http://www.w3.org/2001/XMLSchema — XML Schema Definition

SOAP Fault Messages

Error responses use the <soap:Fault> element within the Body:

<soap:Body>
  <soap:Fault>
    <faultcode>soap:Client</faultcode>
    <faultstring>Invalid user ID</faultstring>
    <detail>
      <errorCode>USR-404</errorCode>
    </detail>
  </soap:Fault>
</soap:Body>

Formatting Fault messages clearly displays the error hierarchy: fault code, human-readable message, and structured detail.

Formatting Tips for SOAP

• Indent the Body content consistently so the actual business payload stands out from the envelope boilerplate.
• Keep namespace declarations on the root Envelope element for clarity.
• When SOAP messages contain embedded XML (e.g., Base64-encoded XML in a string element), decode and format that content separately.