I want to store a password for a webservice in a constant. Of course it should n

If you don't want to store the clear text password in your constant, you can store it in an encrypted or obfuscated form and then run it through an expression which converts it back to clear text right before sending it to the web services smart service. See the plugin "Java Cryptography Architecture (JCA) Tools" under "Shared Components" section for how you can decrypt a string in an expression.