Further questions. Suppose I define the mapping between books and
authors both ways, like this:
<mapping>
<class name="ibm.xml.castor.Book" identity="isbn">
<map-to table="dw_books"/>
<field name="isbn" type="string">
<sql name="isbn" type="varchar" />
</field>
<field name="title" type="string">
<sql name="title" type="varchar" />
</field>
<field name="authors" type="ibm.xml.castor.Author"
collection="arraylist">
<sql name="author_id"
many-table="dw_books_authors"
many-key="book_isbn" />
</field>
</class>
<class name="ibm.xml.castor.Author" identity="id">
<map-to table="dw_authors" />
<field name="id" type="int">
<sql name="id" type="integer" />
</field>
<field name="firstName" type="string">
<sql name="first_name" type="varchar" />
</field>
<field name="lastName" type="string">
<sql name="last_name" type="varchar" />
</field>
<field name="books" type="ibm.xml.castor.Book"
collection="arraylist">
<sql name="book_isbn"
many-table="dw_books_authors"
many-key="author_id" />
</field>
</class>
</mapping>
So now I have in the Author class a collection of Book instances.
Now, let me update my test program:
public class SQLTester {
public static void main(String args[]) {
try {
JDOManager.loadConfiguration("jdo-conf.xml");
JDOManager jdoManager = JDOManager.createInstance("bmclaugh");
Database database = jdoManager.getDatabase();
database.setAutoStore(true);
database.begin();
Author author = new Author(1001, "Joseph", "Conrad");
Author author2 = new Author(1002, "Ford Madox", "Ford");
Book book = new Book("1892295490", "Heart of Darkness", author);
Book book2 = new Book("0451530500", "The Secret Agent", author);
List authorList = new LinkedList();
authorList.add(author); authorList.add(author2);
Book book3 = new Book("0742626539", "The Inheritors",
authorList);
database.create(book); database.create(book2); database.create
(book3);
database.commit();
database.begin();
Author conrad = (Author)database.load(Author.class, 1001);
System.out.println("Located author " + conrad.getFirstName() +
" "
+ conrad.getLastName());
System.out.println("Books:");
for (Iterator i = conrad.getBooks().iterator(); i.hasNext(); ) {
Book conradBook = (Book)i.next();
System.out.println(" " + conradBook.getTitle());
}
database.commit();
database.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
Here, I'm creating several books and several authors, all related. As
expected, using setAutoStore() makes sure I only have to commit my
books, and all the authors get committed as well. Additionally, I can
verify all the entries are correctly persisted.
If I load the Author with ID 1001, I would expect the books property
to get populated, based on the data within dw_books_authors; but
that's not the case. The author is correctly loaded, but his books
are missing (empty list). At face value, I can see that in my
instances of Author at the top, I never assign anything to the books
property; however, I would assume that when Castor loads the author
from the database, it auto-populates the books property using the
values in the dw_books_authors many-to-many table.
Right? Wrong? What am I missing, Werner? :-)
BTW, the exact output is:
Located author Joseph Conrad
Books:
Thanks
---
Brett McLaughlin
Series Editor, Head First
O'Reilly Media, Inc.
Phone: (972) 722-6252
Fax: (972) 692-7958
E-Mail: [EMAIL PROTECTED]
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