Publishing a SOAP Web Service in SAP: From Function Module to WSDL

OData and REST get all the attention, but in real projects SOAP is still everywhere: banks, logistics partners, government portals and older middleware often expect a WSDL. The good news: on an SAP ABAP system, publishing a SOAP service from an existing function module takes about fifteen minutes.

We will build a small service that returns basic material data for a material number.

This is the classic, on-premise way (S/4HANA or ECC). For new developments in ABAP Cloud, prefer OData/RAP; in S/4HANA Cloud, SOAP services are provided through communication arrangements.

#1. A remote-enabled function module

Web services generated from a function module (inside-out) require a remote-enabled module. All parameters must be passed by value.

First a structure for the result:

@EndUserText.label : 'Material info for web service'
@AbapCatalog.enhancement.category : #NOT_EXTENSIBLE
define structure zs_ws_material_info {
  matnr : matnr;
  maktx : maktx;
  mtart : mtart;
  matkl : matkl;
  meins : meins;
}

Then the function module (SE37 or ADT). Under Attributes, select Remote-Enabled Module:

FUNCTION z_ws_get_material_info
  IMPORTING
    VALUE(iv_matnr)    TYPE matnr
    VALUE(iv_language) TYPE spras DEFAULT sy-langu
  EXPORTING
    VALUE(es_material) TYPE zs_ws_material_info
    VALUE(ev_message)  TYPE bapi_msg.

  " Remote-enabled module (SE37 → Attributes → Remote-Enabled Module).
  " All parameters are passed by value – required for RFC and web services.

  DATA matnr TYPE matnr.

  " The caller sends the external format (e.g. without leading zeros)
  CALL FUNCTION 'CONVERSION_EXIT_MATN1_INPUT'
    EXPORTING  input  = iv_matnr
    IMPORTING  output = matnr
    EXCEPTIONS OTHERS = 1.
  IF sy-subrc <> 0.
    ev_message = |Invalid material number { iv_matnr }|.
    RETURN.
  ENDIF.

  SELECT SINGLE FROM mara AS m
    LEFT OUTER JOIN makt AS t ON t~matnr = m~matnr
                             AND t~spras = @iv_language
    FIELDS m~matnr, t~maktx, m~mtart, m~matkl, m~meins
    WHERE m~matnr = @matnr
    INTO CORRESPONDING FIELDS OF @es_material.

  IF sy-subrc <> 0.
    ev_message = |Material { iv_matnr } not found|.
  ENDIF.

ENDFUNCTION.

Two details that save time later:

• Return a message field instead of raising exceptions — SOAP clients handle a filled field far better than a SOAP fault for "not found".
• Apply conversion exits yourself (here MATN1): the caller sends the external format.

#2. Create the service definition

In SE37 choose Utilities → More Utilities → Create Web Service → From the Function Module (or in SE80: Create → Enterprise Service). The wizard asks for:

1. Service definition name — e.g. ZWS_MATERIAL_INFO, plus a short description.
2. Endpoint — our function module. Leave Map Name unchecked if you want the element names to stay exactly IV_MATNR, ES_MATERIAL.
3. SOAP profile — the security level of the service.
4. Package and transport request.

I recommend user and password with transport guarantee — authentication over HTTPS only. Activate the service definition at the end.

#3. Create the binding in SOAMANAGER

The service definition only describes the interface. To make it callable, you need a binding (endpoint):

1. Start transaction SOAMANAGER (opens in the browser).
2. Service Administration → Web Service Configuration, search for ZWS_MATERIAL_INFO.
3. On the Configurations tab click Create Service, enter a service and binding name.
4. Security: Transport Guarantee = HTTPS, Authentication = User ID/Password.
5. Save — the binding is active immediately.

With Open Binding WSDL Generation you get the WSDL URL. This is the link you send to the partner.

#4. Test the service

Import the WSDL into SoapUI (or Postman), set basic authentication and send a request:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
                  xmlns:urn="urn:sap-com:document:sap:rfc:functions">
  <soapenv:Header/>
  <soapenv:Body>
    <urn:Z_WS_GET_MATERIAL_INFO>
      <IV_MATNR>MAT-1000</IV_MATNR>
    </urn:Z_WS_GET_MATERIAL_INFO>
  </soapenv:Body>
</soapenv:Envelope>

The answer:

<soap-env:Envelope xmlns:soap-env="http://schemas.xmlsoap.org/soap/envelope/">
  <soap-env:Header/>
  <soap-env:Body>
    <n0:Z_WS_GET_MATERIAL_INFOResponse xmlns:n0="urn:sap-com:document:sap:rfc:functions">
      <ES_MATERIAL>
        <MATNR>MAT-1000</MATNR>
        <MAKTX>Laptop 14 Developer Edition</MAKTX>
        <MTART>HAWA</MTART>
        <MATKL>IT01</MATKL>
        <MEINS>ST</MEINS>
      </ES_MATERIAL>
      <EV_MESSAGE/>
    </n0:Z_WS_GET_MATERIAL_INFOResponse>
  </soap-env:Body>
</soap-env:Envelope>

The caller needs an SAP user with authorisation for the service — object S_SERVICE (and S_RFC for the function group). A system or communication user with a narrow role is the clean solution.

#5. When something goes wrong

In SRT_UTIL you can switch on a payload trace for a user for a limited time — the fastest way to see what was actually sent.

#Summary

• Remote-enabled function module, parameters by value, messages instead of exceptions.
• Service definition from the wizard, security profile with HTTPS.
• Binding in SOAMANAGER, WSDL URL to the partner.
• Test in SoapUI, analyse with SRT_UTIL.

SOAP is not glamorous, but it is reliable — and with these steps a partner integration that "needs a WSDL" is no longer a reason to worry.