Question

i create two domain, Author and Book, the Author has many Book, and the Book is belongsTo Author.

class Author {
     hasMany = [ books : Book ]
     String name
}

class Book {
    String title
    Author author
}

this “savebook” function in BookController.groovy

   def savebook={

        def json = request.JSON
        def bookInstance = new Book()
        bookInstance.properties = json

        bookInstance.author_id = json.author_id
        bookInstance.title = json.title         

        if (bookInstance.validate()) {
            bookInstance.save();
            def rep = [ respence: "1" ] // save
            render rep as JSON
        }

        else {
            def rep = [ respence: "0" ] // not save
            render rep as JSON
        }

    }

I have not found a solution for the line : bookInstance.author_id = json.author_id in “savebook” to create a book by an author.
My second question is how should be the structure of the JSON object to make a REST POST ?

Answer 1

For the first part of your question you need to look the author up by their id and assign that instance to the author variable in Book:

def author = Author.get(json.author_id)
bookInstance.author = author
bookInstance.title = json.title
author.addToBooks(bookInstance)

The structure of the JSON coming into the rest method can be any valid JSON. You could simply do

{
    "author_id": 12345,
    "title" : "See Jane Run"
}

or you could get as complicated as you need.