OrientDB one to many using Object API

Question

I'm using the Object API with OrientDB, and I need to change one of my fields. I currently have something like:

class Book { String author }

But I want to change it to:

class Book { List<String> authors }

My question is: how do I persist this list of Strings in OrientDB? Do I have to declare the list as @Embedded? Do I have to define the Schema as LINKLIST?

I tried the latter, which resulted in:

Caused by: java.lang.ClassCastException: java.lang.String cannot be cast to com.orientechnologies.orient.core.db.record.OIdentifiable

And, if I make the type in the database an Embbed, then it results in the error:

Caused by: java.lang.IllegalArgumentException: Type EMBEDDED must be a multi value type (collection or map)

Which doesn't provide to much information unfortunately.

So, how can I best fix this?

Answer 1

Start point: I created a new db from the Java API, and I saved a list of authors.

CLASS BOOK

public class Book {

private List<String> authors;

public void setAuthors (List<String> pAuthors){
    this.authors = pAuthors;
}

public List<String> getAuthors(){
    return this.authors;
}

}

CLASS MAIN

public class DatabaseTipoObject {

private static String remote="remote:localhost/";

public static void main(String[] args) {
    String nomeDb="Object";
    String path=remote+nomeDb;

    try {
        OServerAdmin serverAdmin = new OServerAdmin(path).connect("root", "root");
        if(serverAdmin.existsDatabase()){   
            System.out.println("Database '"+nomeDb +"' exist..");
        }
        else{ 
            serverAdmin.createDatabase(nomeDb, "object", "plocal");
            System.out.println(" Database '"+nomeDb +"' created!..");
        }

        OObjectDatabaseTx db = new OObjectDatabaseTx (path);
        db.open("root","root");

        db.getEntityManager().registerEntityClass(Book.class);
        Book book = db.newInstance(Book.class);
        List<String> myAuthors = new ArrayList();
        myAuthors.add("Archimede");
        myAuthors.add("Pitagora");
        book.setAuthors(myAuthors);

        db.save(book);
        System.out.println("Data inserted!" );

        //get info by query
        for (Book book_retrive : db.browseClass(Book.class)) {
            System.out.println("#: " +book_retrive.getAuthors().get(0) );
            System.out.println("#: " +book_retrive.getAuthors().get(1) );
        }

        db.close();

        serverAdmin.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

From Studio: the object 'Book' was created, and it has the field 'authors' as embeddedlist. (Created automatically)