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From: Niclas Hedhman <niclas@hedhman.org>
Date: Wed, 5 Jul 2017 15:26:43 +0800
Message-ID: <CADmm+KejcRzxRZz-MN+jP=OC6nZh-V4on-ouaAuK4oCP_W-R3g@mail.gmail.com>
Subject: Why I don't like regular expressions...
To: dev@polygene.apache.org
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archived-at: Wed, 05 Jul 2017 07:27:10 -0000

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We have

private static final Pattern DESCRIPTOR_TEXTUAL_REGEXP = Pattern.compile(
    "^"
    + Pattern.quote( DESCRIPTOR_COMPONENT_SEPARATOR_START ) + "(.*)"
    + Pattern.quote( DESCRIPTOR_COMPONENT_SEPARATOR_END )
    + Pattern.quote( DESCRIPTOR_COMPONENT_SEPARATOR_START ) + "(.*)"
    + Pattern.quote( DESCRIPTOR_COMPONENT_SEPARATOR_END )
    + Pattern.quote( DESCRIPTOR_COMPONENT_SEPARATOR_START ) + "(" + "[^"
    + Pattern.quote( DESCRIPTOR_COMPONENT_SEPARATOR_END +
DESCRIPTOR_TYPE_SEPARATOR )
    + "]+)" + Pattern.quote( DESCRIPTOR_COMPONENT_SEPARATOR_END ) + "$" );


in org.apache.polygene.index.sql.support.skeletons.AbstractSQLStartup

And in method stringToCompositeDescriptor()

Matcher matcher = DESCRIPTOR_TEXTUAL_REGEXP.matcher( str );
if( !matcher.matches() )
{
    throw new IllegalArgumentException( "Descriptor textual description " + str
                                        + " was invalid." );
}

and of course it says that it doesn't match with

{Domain Layer}{Organization Module}{interface
com.sensetif.sink.model.organization.CreditLimit,interface
org.apache.polygene.api.value.ValueComposite}


so where is the problem?


The RegExp "Pattern" prints out to

^\Q{\E(.*)\Q}\E\Q{\E(.*)\Q}\E\Q{\E([^\Q},\E]+)\Q}\E$

as if that helps...

So I realize that the \Q and \E are escaping markers, so it is basically
saying

^{(.*)}{(.*)}{([^},]+)}$

(where comma and curlies being ordinary characters)

But the third group shouldn't work at all...

* ([^},]+)*

So, that is a group of one or more characters but not comma and not end
brace...


Has this ever worked? Because a few lines later, the sequence of types are
being extracted, so it was intended to have multiple types.


I am at loss.


Cheers
-- 
Niclas Hedhman, Software Developer
http://polygene.apache.org - New Energy for Java

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