+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. > > -- > This message is automatically generated by JIRA. > If you think it was sent incorrectly, please contact your JIRA > administrators: > https://issues.apache.org/jira/secure/ContactAdministrators!default.js > pa For more information on JIRA, see: > http://www.atlassian.com/software/jira > > >
