WSDL Validator: "Cannot read schema null" with inline xsd schemas

[paulhyo]

Hello

We tried to integrate a partner wsdl in a serviceProxy to validate the soap content.

I get a Configuration Error when starting Membrane:

************** Configuration Error ***********************************

Cannot create message validator.

Reason: Cannot read schema null.


Giving up.

Check proxies.xml file for errors.

Membrane terminated with exit code 1
MEMBRANE_HOME: /opt/membrane
CLASSPATH: /opt/membrane/conf:/opt/membrane/lib/*

I think the problem comes from the WSDL structure which includes inline xsd schema.

Here is a simplified version for testing:
wsdl_with_inline_schema.wsdl.txt

Is it case? if yes, is a fix possible? I can use this wsdl (even if it's not very clean) in other tools/products (SoapUI / IBM Datapower) without problem...

[predic8]

Hello @paulhyo ,

thank you for the error description.

Membrane can read and process the WSDL for the WSDL Publisher and WSDL Rewriter. These components do not require strict XML Schema resolution and can therefore handle WSDLs that contain multiple inline xsd:schema blocks.

However, Validation uses a different mechanism. It is based on standard-compliant XML Schema validators (Xerces/Saxon class). These validators follow the W3C Schema specification, which requires that every referenced namespace must be imported from a separate schema document, not from another inline schema fragment inside the same WSDL.

Because your WSDL contains several inline xsd:schema elements with different target namespaces, the validator cannot resolve types across these schema blocks. This leads to:

Cannot create message validator.
Reason: Cannot read schema null.

For validation to work, the inline schemas must be extracted into external .xsd files, and the top-level schema must explicitly import them using real schemaLocation URIs.
For example:

<xsd:schema elementFormDefault="qualified"
            targetNamespace="http://www.uid.admin.ch/xmlns/uid-wse">

    <xsd:import namespace="http://www.uid.admin.ch/xmlns/uid-wse-shared/2"
                schemaLocation="uid-wse-shared.xsd"/>

    <xsd:import namespace="http://www.uid.admin.ch/xmlns/uid-wse/5"
                schemaLocation="uid-wse-5.xsd"/>

    <xsd:import namespace="http://www.ech.ch/xmlns/eCH-0108/5"
                schemaLocation="eCH-0108-5.xsd"/>

    <xsd:import namespace="http://microsoft.com/wsdl/types/"
                schemaLocation="ms-types.xsd"/>

    <xsd:import namespace="http://www.ech.ch/xmlns/eCH-0097/5"
                schemaLocation="eCH-0097-5.xsd"/>
</xsd:schema>

This structure works for validation, because each namespace is backed by a dedicated external XSD file.

If that workaround does not work for you. Please let me know. We can could preprocess the schemas to provide the needed structure for the validator so that it could process it.

Cheers
Thomas

[paulhyo]

Hi Thomas,

I already defined the new structure with the external schemas so that the project is not blocked. We will take this restriction (no inline XSD) into account and apply it to external projects. Internally, the use of specific XSD schemas is already a rule.

Thank you
Best regards

Stéphane