GraphQL Mutation with Same input and Type object using Spring for graphQL

Question

I had a problem with Spring for GraphQL, I was trying to add a book to an existing static list of book using mutation. How to achieve it ?

If my schema is,

type Mutation {
   addBook(book: Book): Book 
}  

type Book {
   id: ID!
   name: String!
   author: Author 
}  

type Author {
   id: ID!
   fname: String!   
   lname: String
}

and I try to do at the java layer as,

@MutationMapping
public Book addBook(Book book) {
    Book.addBook(book);
}

I am getting error stating that Book is not input param (Consider Book is a record type having a static list and add method). Now to fix it when I am adding another BookInput input type in schema,

input BookInput {
   id: ID!
   name: String!
   author: Author 
} 

it is saying Author is not an input type. Now if I go ahead with another AuthorInput in my schema how will it resolve that correlation (do I need to write another SchemaMapping for the BookInput type and author field). Also isn't this a lot of redundant coding ? I am sure there is a way to avoid all of it. Please advise.