There are some interesting ideas here. (the integer / string comparisons,
for example)
Have you thought about this not being supported directly in the core (in the
nodes), but as an 'external' in-context toolkit?
I am going to take tomorrow off (I hope) to catch up on some promises re
Vel, so I will get to play with it then...
On 12/11/01 10:00 PM, "Will Hartung" <[EMAIL PROTECTED]> wrote:
> Hi all!
>
> I've gone and made a couple of changes to Velocity to help support my
> project, and I thought I'd share them with the masses.
>
> Earlier, I made a change to let the comparison routines support
> "Compareable" objects. After playing with that, it wasn't what I needed.
>
> So, now I've added support for a new class
> org.apache.velocity.util.VelocityValue.
>
> VelocityValue is a "multi-typed" value.
>
> All of these "work"
>
> new VelocityValue(1.0); // These are doubles
> new VelocityValue(new Integer(1)); // It's still a double internally
> new VelocityValue("Neato"); // Strings
> new VelocityValue(new java.util.Date); // Dates
> new VelocityValue(true); //Booleans
> new VelocityValue(new Boolean(true)); // Same thing
>
> Once things are placed into VelocityValues, you can do pretty normal things
> with them.
>
> Math and comparions, specifically.
>
> For Math, I've changed the internals of the interpreter.
>
> The interpreter now knows how to perform Math on Integers, Strings, and
> VelocityValues.
>
> // Assume:
> // context.put("vInt", new VelocityValue(1));
> // context.put("vStr", new VelocityValue("Bob"));
> // context.put("vStrN, new VelocityValue("123"));
> // context.put("vDate", new VelocityValue(new java.util.Date())); // Dec
> 11, 2001
>
> #set ($foo = 1 + 1) // result is an Integer, 2
> #set ($foo = 1 + $vInt) // result is an Integer, 2
> #set ($foo = $vInt + 1) // result is a VelocityValue, 2
> #set ($foo = "This" + "That") // result is a String, "ThisThat"
> #set ($foo = "This" + $vStr) // result is a String, "ThisBob"
> #set ($foo = $vStr + "That") // result is a VelocityValue, "BobThat"
> #set ($foo = $vStrN + "4") // result is a VelocityValue, "1234"
> #set ($foo = 1 + $vStrN) // result is an Integer, 124
> #set ($foo = 1 + "234") // result is an Integer, 235
> #set ($foo = "1" + 1) // result is a String, "11"
> #set ($foo = $vDate + 1) // result is a VelocityValue, "tomorrow" (Dec 12,
> 2001).
> #set ($foo = 1 + $vDate) // result is a Integer, 1 (objects used is where
> they "don't belong" are "nothing", the result is the left hand side of the
> expression.)
>
> Note that the left hand side of the equation determines the result type.
>
> You can compare object of like type, and as in normal expressions, the left
> hand side will coerce the right hand side for comparisons.
>
> #if (1 < 2) true #end
> #if ("1" < "2") true #end
> #if(1 < "2") true #end
> #if("10000" < 1234) true #end // This is non-obvious, but "10000" is less
> than "1234"
> #if(1234 < "10000") true #end // Don't try this stuff at home, kids.
>
> This works as well:
> $if($vInt) // or any VelocityValue
>
> VelocityValues support asString, asNumber, asBoolean, and asDate, that you
> can then apply other methods to (like substring, for example). They will
> automatically convert for you. So, #set($foo = $vInt.asString() + 1) = "11"
> (Integer value converted to String coerces + to string expression,
> converting 1 to "1").
>
> One last thing, for you SQL folks out there. VelocityValues support NULLS.
> Any math with NULLS results in a NULL value, however any comparision with
> NULL results in FALSE. Note that SQL NULLs are different from Java Null.
> They're there if you want them. There is an isNull() method.
>
> For conversions:
> To Number:
> Strings convert to the base 10 numbers, otherwise 0.
> Dates convert to their number of seconds since epoch.
> Booleans are 0 or 1
>
> To String:
> Pretty standard. There isn't any way to control the Date format at the
> moment.
>
> To Date:
> Convert to a number, and use that number as the number of seconds since
> epoch.
>
> To Boolean:
> 0 = false, "" = false, NULL is false, everything else is true.
>
> A couple of key things to note.
>
> I strived to maintain backward compatability, even within the implemenation.
> For example, for the Math and Comparisons, it still uses the same code if
> you pass in Integers instead of VelocityValues or Strings. Before, it would
> check for Integers and Do The Right Thing, or raise an error. Now, rather
> than raising an error, it does Other Things. This specifically means that
> there shouldn't be any extra cost if you use Velocity without
> VelocityValues.
>
> The exceptions here are that where in the past things like #if(1 < "2")
> would raise an error, now they Do Something. This means that they don't
> necessarily return false (like they do now). (so, for example, the logical
> test in the test suite currently fails).
>
> The other issue is that, of course, I haven't changed how things are parsed.
> So, for example, you can't put floats into your scripts yet. You also cannot
> create VelocityValues within scripts. You can do sick things like
> #($vInt.setValue("1.2")) which will set the internal value to a String of
> 1.2, and will then convert it to a double. So, $vInt * 10 would equal 12.
>
> I don't really plan on doing that, personally. Do your logic in Java, I say.
> :-)
>
> It hasn't been really beat on yet, I'll be doing that tomorrow. Also, the
> patch has a couple of System.out.println debug things left in there, but
> they can be easily removed.
>
> Anyway, the patch is attached. I'd appreciate any comments. I'm particularly
> interested in weird exceptions, etc. One thing it doesn't do right now is
> Date subtraction. (Date1 - Date2 = # of days)
>
> The patch is applied at the src/java/org/apache level.
>
> $ cd $velhome/src/java/org/apache
> $ patch -d . -p0 < /tmp/patch.out
>
> Regards,
>
> Will Hartung
> ([EMAIL PROTECTED])
>
>
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--
Geir Magnusson Jr. [EMAIL PROTECTED]
System and Software Consulting
"He who throws mud only loses ground." - Fat Albert
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