pattern for JPA Entity facilitator methods

What data structure pattern should be used along with JPA for writing facilitator methods?

I'm using Hibernate JPA and have almost 2 dozen @Entity. Current structure of my application is

| Controller Layer | --> | Service Layer | --> | Data Access Layer |

My service layer has lots of business rules. Dummy E.g. Employee entity has manager column variable. Business Rule is he/she is a manager if MANAGER column is having NULL value. Else he/she is reporting to some manager.

As part of single responsibility principle I would go and write a method in Employee entity which will return boolean.

public boolean isManager() { return this.manager == null; }

My problem is I need half a dozen such facilitator methods in Entity. Should I write it in Enity or should I consider any other pattern for that? which pattern should I try for such case?

PS: based on the facilitator methods(business rules) i want to use entities for persisting back or other crud operations.