Re: [p2-dev] classes deleted from provisional API

[Thomas Hallgren <thomas@xxxxxxx>]

Some comments in-line.

On 01/23/2010 12:34 AM, Ian Bull wrote:
> Actually, regarding Capability queries, I think (don't quote me ;)), you can
> just take the existing required capability that you have and call
> getMatches(). This will return a query that when executed will find all IUs
> that provide a capability that matches your requirement.
>
>    
The canonical form of an IRequrement is an expression that is matched 
against an IInstallableUnit. Consequently, the IRequrement.getMatches() 
returns an expression. An expression can be transformed into a query 
using an ExpressionQuery. Thus the former:

 new CapabilityQuery(cap);

can be written as:

 new ExpressionQuery(IInstallableUnit.class, cap.getMatches());

or, using Java 5 generics:

 new ExpressionQuery<IInstallableUnit>(IInstallableUnit.class, 
cap.getMatches());


> > 2. IUPropertyQuery. We're not sure what's going to happen to this yet,
> > that's why it's still internal.  But you should be able to use the p2ql for
> > this.
> >
> >   QLMatchQuery qlMatchQuery = new QLMatchQuery(IInstallableUnit.class,
> > "properties['foo'] == 'true'");
> > This will match all IUs with a property key == foo, with a value == true.
> >   Or, more generally:
> > QLMatchQuery qlMatchQuery = new QLMatchQuery(IInstallableUnit.class,
> > "properties[$0] == $1", new String[] {"foo", "true"});
> >
> > Notice the use of parameters here.
> >
> >      
The p2QL is an extension to the more generic IExpression used by the 
metadata package. It adds collection processing like arrays, 
select/collect/latest/first/flatten/traverse, and translation support to 
the expression language. Unless you need that you can use the 
expressions directly and avoid the extra bundle:

Java 5 syntax:

 new ExpressionQuery<IInstallableUnit>(IInstallableUnit.class,
    ExpressionUtil.parse("properties[$0] == $1"), "foo", "true");

without generics and varargs:

 new ExpressionQuery(IInstallableUnit.class,
    ExpressionUtil.parse("properties[$0] == $1"), new Object[] {"foo", 
"true"});


> > 3. CapabilityQuery. This one I'm not so sure about. Pascal was doing some
> > work using Expressions&  queries to compute capabilities.  Pascal, can you
> > help out here?
> >
> >      
The details behind the current API are explained here:

 https://bugs.eclipse.org/bugs/show_bug.cgi?id=298604#c13

Regards,
Thomas Hallgren