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Subject: Re: [Configuration]JEXL question
From: Ralph Goers <ralph.goers@dslextreme.com>
In-Reply-To: <E7C43D14-9932-4F76-B59F-75ADBE39957C@dslextreme.com>
Date: Sat, 29 Aug 2009 11:09:55 -0700
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On Aug 29, 2009, at 10:35 AM, Ralph Goers wrote:

>
> On Aug 29, 2009, at 6:33 AM, rzo wrote:
>
>> Hello,
>>
>> thanks for mentioning jexl scripting.
>> I tried it out and have found the following issue:
>>
>> evaluating the following:
>>
>> test=${expr:if (System.getProperty("user.home").startsWith("C"))  
>> {"x";} else {"z";}}
>>
>> does not seem to work.
>> Debuging shows that the expression forwarded to jexl is:
>>
>> if (System.getProperty("user.home").startsWith("C")) {"x";
>>
>> is this a bug ? or is there a way to escape the brackets within $ 
>> {...} ?
>>
>
> The "bug" is actually the way  
> org.apache.commons.lang.text.StrSubstitutor works. It can configured  
> be with prefix and suffix characters - the defaults are '{' and '}'  
> and after finding the prefix it just searches for the first  
> occurance of the suffix character - unless it finds a recursive  
> variable. So the string passed to ConfigurationInterpolator is what  
> you show above.
>
> However, it might be possible to override the suffix matcher to look  
> for an escape character.
>

It occurs to me though that just using a different suffix matcher will  
not remove the escape character.

One other thought. StrSubstitutor allows the prefix and suffix  
characters to be replaced, so you should be able to do

conf.getSubstitutor().setVariablePrefix('`');
conf.getSubstitutor().setVariablesuffix('`');

and then use test="$`expr:if (System.getProperty 
("user.home").startsWith("C")) {"x";} else {"z";}`

It also supports using strings so you could do:

conf.getSubstitutor.setVariableSuffix("$}";

and then test="${expr:if (System.getProperty("user.home").startsWith 
("C")) {"x";} else {"z";}$}

Of course, then you would have to use those prefix and suffix  
characters throughout that configuration.

Ralph


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