Queries

Shades has an interesting way of doing queries. It's based on the idea of a RecordCandidate. I find it much easier to explain this using code than with a paragraph.

The following code returns all the Books, in a List;

ORMDictionary dict = MyORMDict.getInstance();
Query query = QueryFactory.newQuery(dict);
RecordCandidate aBook = query.candidate(dict.getORM("BOOK"), "aBook");
RecordSet rs = dbSession.executeQuery(jdbcConn, query);
List books = new ArrayList();
rs.populateList(books, Book.class);

There are several cool things:
1) The books got put into MY list (not a proxy List created by the data access framework).
2) There is no query language. Shades uses a new form of query-by-example. In the example
above the query is told what to retrieve by requesting a candidate.
3) I passed the jdbcConnection into the query (This means I control transactions using the JDBC transaction model).

Why did we request a RecordCandidate if we did didn't use it for anything. Well OK then, let's use it for something. In the query below we retrieve only the books authored by william gibson.

ORMDictionary dict = MyORMDict.getInstance();
Query query = QueryFactory.newQuery(dict);
RecordCandidate aBook = query.candidate(dict.getORM("BOOK"), "aBook");
RecordCandidate anAuthor = query.candidate(dict.getORM("AUTHOR"), "anAuthor");
anAuthor.where("NAME like 'william Gibson'");
aBook.relatedTo(anAuthor, "book->author");
RecordSet rs = dbSession.executeQuery(jdbcConn, query);
List books = new ArrayList();
rs.populateList(books, Book.class);

Shades let you bust into a query and insert your own SQL. You can see that on the line above that says "anAuthor.where...""
Dangerous? maybe, but fear not. shades encourages you to encapsulate your queries inside the ORMDictionary, and to parameterize them. Once yo've done that, there is no hint of SQL in the code, which subsequently looks like this:

ORMDictionary dict = MyORMDict.getInstance();
dbSession.setParameter("authorName", "william gibson");
RecordSet rs = dbSession.executeQuery(jdbcConn, dict.getQuery("query:book-by-auth"));
List books = new ArrayList();
rs.populateList(books, Book.class);


Here is another very cool thing about Shades queries. They, by default, return ALL the candidates that participate in the relationship graph. So in fact, you can retrieve the Book AND its author from the RecordSet, like this:

Book book = new Book();
Author author = new Author();
while(rs.hasNext()){
rs.populate(book, aBook);
rs.populate(author,anAuthor );
System.out.println(book.title +" was authored by " + author.name);
}