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Update placeholder docs to mention env vars and default values 

See gh-30012
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Kirill Marchuk 2022-02-28 17:36:25 +02:00 committed by Andy Wilkinson
parent ef927627de
commit 2644a2b897
1 changed files with 4 additions and 4 deletions
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8
spring-boot-project/spring-boot-docs/src/docs/asciidoc/features/external-config.adoc
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@ -443,16 +443,16 @@ For example, if a secret named `db.password` is mounted at location `/run/secret
[[features.external-config.files.property-placeholders]]
==== Property Placeholders
The values in `application.properties` and `application.yml` are filtered through the existing `Environment` when they are used, so you can refer back to previously defined values (for example, from System properties).
The standard `$\{name}` property-placeholder syntax can be used anywhere within a value.
The values in `application.properties` and `application.yml` are filtered through the existing `Environment` when they are used, so you can refer back to previously defined values (for example, from System properties or environment variables).
The standard `$\{name:default}` property-placeholder syntax can be used anywhere within a value.
For example, the following file will set `app.description` to "`MyApp is a Spring Boot application`":
For example, the following file will set `app.description` to "`MyApp is a Spring Boot application written by john.doe`":
[source,yaml,indent=0,subs="verbatim",configblocks]
----
app:
name: "MyApp"
description: "${app.name} is a Spring Boot application"
description: "${app.name} is a Spring Boot application written by ${USERNAME:john.doe}"
----
TIP: You can also use this technique to create "`short`" variants of existing Spring Boot properties.