Depends on what you want. Out of the box Weblogic supports TLS upto 1.2, see your other question.
You can use OWSM Policies that can do X509 encryption on messages and or other security. But I'm not sure you mean that.
To my knowledge there is no xpath function that does encryption of specific elements.
So what kind of encryption/decryption are you looking for?
Like soa 12c composites, we have a default OOTB encryption and decryption which we can add them from services and reference section of composite.xml. I am looking for such type of method of adding the encryption and decryption feature. Do we have any such technique or else?
This "default OOTB encryption and decryption" are that services, java classes, or something like that?
You can use either spring components (see https://blog.darwin-it.nl/2018/09/zipping-is-easy-in-javaspringsoasuite.html ), or embedded java to call those, if you have the components in the class path of the server. I favor spring components strongly, I'm have grown to dislike complex embedded java snippets.
Keys can be stored in the Credential Store framework, which can be fetched using java APIs. A colleague sorted out how to do this, but I need to create an article on it.