The default XSLT processor shipped in with WSO2 ESB is xalan. Let's assume that you need to change the xslt processor to saxon.
Following are the steps to set saxon as the XSLT processor.
1) Remove the xalan-2.7.0.wso2v1.jar from the following locations.
2) Then add the Saxon home edition(saxon9he.jar) to the above mentioned locations.
Saxon can be downloaded from .
3) Start the ESB server.
After changing the XSLT processor to Saxon, you can do your transformations with the use of Saxon parser.
 - http://saxon.sourceforge.net/