DAO Best practices : Querying Parent / Children

Given you have a domain model with a simple parent / child relationship, and each entity has it's own associated DAO, eg:

Author
AuthorDAO
Book
BookDAO

If I want to add a DAO method for retrieving the books by a specific author, what's the best place for it?

class AuthorDAO
{
    List<Book> getBooks(Author autho开发者_如何学编程r);
}

or

class BookDAO
{
    List<Book> getBooks(Author author)
}

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I'd place a Book finder on the BookDAO. This is where I would expect it to be, regardless of its parameters. If you want to find a book, you don't want to scan all DAOs to find where the right finder is. Putting it somewhere else won't help the users of the API.

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The BookDAO, because you want to get information about books. The Book is the main subject here.