John Huss created CAY-1724:
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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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