Add support for default values in property placeholder syntax [SPR-4785]

[spring-projects-issues]

Kenny MacLeod opened SPR-4785 and commented

I'd like to be able to specify the defaults for property placeholders within the placeholder itself, perhaps with something like this:

${my.property:myDefaultValue}

or something similar.

My use case is that often it is desirable to have to defaults alongside the placeholder, for readability. Also, our applications use a single, globally-defined placeholder configurer, and different instances of the application have different property sets, decoupled from the code itself. Embedding defaults within the placeholders would make this much easier to manage.

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Affects: 2.5.4

Issue Links:

• Property placeholder defaulting in resources path [SPR-5508] #10180 Property placeholder defaulting in resources path

3 votes, 5 watchers

[spring-projects-issues]

Juergen Hoeller commented

Good news: Such placeholder defaulting has been discussed already and is very likely to make it into Spring 3.0!

Juergen

[spring-projects-issues]

Ben Rowlands commented

An alternative syntax for separating the default is the ksh style "VALUE:-DEFAULT". It makes it slightly easier to read by adding extra distance between the variable name and the default. See "Korn Shell Variable Usage and Setting Rules" in:

• http://www.bo.infn.it/alice/alice-doc/mll-doc/impgde/node16.html

[spring-projects-issues]

Juergen Hoeller commented

I went with the "${myKey:myDefaultValue}" defaulting syntax for 3.0 now. The separator is configurable through PropertyPlaceholderConfigurer's "valueSeparator" property, analogous to "placeholderPrefix" and "placeholderSuffix".

Juergen