Re: Referencing Hash Values from Keys

Tuesday, October 27, 2009, 6:15:48 PM, Shelley, Ryan wrote:

> Well, I think I'm just not familiar with FM yet, and I'm running this as
> a Maven FMPP Ant Task, so what it seems was happening was that it was
> pulling in a different config file than I thought, and that config file
> didn't have a "poolConnections" value in one of the "pools", and since
> FM isn't as lenient with missing keys it was throwing an error.  Looks
> like I need to add some existence checking prior to accessing the hash
> value.  Sorry for the false alarm.  I'm going to keep at it, but I think
> it was just user-error.  Thanks for checking!

FreeMarker wants you to be explicit about optional stuff. (Like in
this case it certainly helped you to find a mistake... you pick up the
wrong config file or something like that.) If you know a variable is
optional (i.e, *validly* missing or null), please use missing value
handler operators:
http://freemarker.org/docs/dgui_template_exp.html#dgui_template_exp_missing

-- 
Best regards,
 Daniel Dekany

> -Ryan
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Daniel
> Dekany
> Sent: Tuesday, October 27, 2009 1:48 AM
> To: FMPP open discussion
> Subject: Re: [FMPP] Referencing Hash Values from Keys
>
> Tuesday, October 27, 2009, 5:45:11 AM, Shelley, Ryan wrote:
>
>> I'm new to Freemarker, but have used other templating languages in
>> the past.  Currently, I'm attempting to use FMPP to generate
>> configuration files, but having a bit of difficulty referencing hash
>> values from keys.  Here is my TDD and sample template:
>>  
>> TDD:
>>  
>> {
>>       pools: [
>>             {
>>                   poolName: Foo
>>                   poolConnections: ServiceA
>>             },
>>             {
>>                   poolName: Bar
>>                   poolConnections: ServiceB
>>             }
>>       ]
>> }
>>  
>> Template:
>>  
>> This will output fine:
>> <#list pools as pool>
>>       <#assign keys = pool?keys >
>>       <#list keys as key>
>>             ${key} = ${pool[key]}
>>       </#list>
>> </#list>
>>  
>> This will get an error on poolConnections:
>> <#list pools as pool>
>>       ${pool.poolName}
>>       ${pool.poolConnections}
>> </#list>
>>  
>> In the first list iteration, everything is output correctly, but I
>> have no control over the keys.  However, the second iteration fails
>> on "${pool.poolConnections}" with the error:
>>  
>> Caused by: freemarker.core.InvalidReferenceException: Expression
>> pool.poolConnections is undefined (notice the error is not on
> pool.poolName)
>>
>> If I take "${pool.poolConnections}" out, it works fine (I see the
>> value for poolName), but I kind of need to be able to access
> "poolConnections"!
>>  
>> I've tried this with different combinations of
>
> Don't... it should work the way you tried to do it:
> pool.poolConnections
>
> I copy-pasted your above snippets into an FMPP project and it works
> fine here. Even if you use different versions than me, I don't know
> about any bugs in FreeMarker or FMPP bugs that would spoil a such
> basic operation. Are you absolutely sure you don't have a typo
> somewhere, and that you look at the files that your project actually
> uses?
>
>> "${pool[poolConnections]}" and "${pool['poolConnections']}" and
>> "${pool.get(poolConnections)}" but none seem to be correct.  I've
>> been back and forth through the documentation and the examples, but
>> none seem to cover accessing a hash value by it's key directly.
>
> FreeMarker documentation does. It's myMap.myKey or
> myMap[WhateverExpressionThatEvaluatesToAString] (like myMap["myKey"]
> or myMap[aVariable], myMap["foo_" + i], etc.).
>
>> Suggestions?  Thanks!
>>  
>> -Ryan
>



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