Grokbase Groups Cayenne dev July 2012
FAQ
+10.
Most ORMs make it incredibly painful to get at the metadata for a column.
Easily generating queries is just one way to put this to use; another would be updates to the database schema (just use the metadata for old and new schema and glue a bit of transformation code between them); a third would be attaching more metadata such as per-property validation or formatting rules.

SimpleORM might be another source of inspiration.
It's architecturally centered around the metadata, not the Pojos, so it might have details differently in an interesting manner.
John Huss created CAY-1724:
------------------------------

Summary: Add 'Property' class for easier and better Expression creation
Key: CAY-1724
URL: https://issues.apache.org/jira/browse/CAY-1724
Project: Cayenne
Issue Type: Improvement
Components: Core Library
Affects Versions: 3.2M1
Reporter: John Huss
Priority: Minor
Attachments: Property.java

Project Wonder (WebObjects) has a class which is basically just a wrapper around an attribute or relationship name that gives you a way to create Expressions in type-safe manner and with minimal effort. Also sort orderings can be easily generated. In Wonder, these "property" objects are part of the entity template so they are generated automatically.

So for example:

public class _Artist extends CayenneDataObject {
public static final Property<String> NAME = new
Property<String>(NAME_PROPERTY); ...
}

Then client code can do things like:

new SelectQuery(Artist.class, NAME.eq("Pablo").andExp(AGE.gt(40)),
AGE.descs());

This would select all artists with name equal to Pablo and age greater than 40 and order them in descending age order.

This concept has been proven to work incredibly well with WebObjects. It's almost as readable as using plain strings but has complete compile-time checking for the property name and the type of the objects it is compared with.

A complete implementation is attached. It's very simple since ExpressionFactory does the work. If this is accepted, it would make sense to modify the built-in entity templates to generate Property constants for all of the properties.

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