Unable to load transformer factory &1

What causes this issue?

An implementation of the TransformerFactory interface is used when an
XSLT mapping is executed. In this instance, the following implementation
should be used: &V1&. However, this implementation could not be called.
Possible causes:
The library that contains &V1& is missing on the Integration Server
The name of the implementation is incorrect

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

The following TransformerFactory is used as the default:
"com.sap.engine.lib.jaxp.TransformerFactoryImpl". This setting can be
overwritten by using the property
"com.sap.aii.mapping.transformerFactory" in the exchange profile (if the
default setting is not used then no Java extension functions can be used
in the XSLT mapping, however).

System Response

How to fix this error?

If &V1& is not the correct implementation, check the property
"com.sap.aii.mapping.transformerFactory" in the exchange profile. If
nothing is maintained there, the default value is used.
If &V1& is identical to the default value
"com.sap.engine.lib.jaxp.TransformerFactoryImpl", check whether the
directory "additional-libs" on the Integration Server J2EEngine contains
the "sapxmltoolkit.jar" Jar.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.