I see two options:
- Setting the credentials as System Properties using -M-Dproperty in command line and retrieving it from your POJO using java.lang.System.getProperty("property")
- Configuring the credentials in a .properties file and retrieve them from the Property placeholder from the Mule Registry. You can implement org.mule.api.context.MuleContextAware perhaps, or a Lookup annotation.
Also read this