Spring/spring-boot
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Clarify documentation for relaxed binding of environment variables

Browse Source 
Closes gh-22974
This commit is contained in:
Andy Wilkinson
2020-11-04 17:40:27 +00:00
parent a8b8f43180
commit d5980be623
1 changed files with 6 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
spring-boot-project/spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc
View File

@@ -1185,9 +1185,6 @@ To convert a property name in the canonical-form to an environment variable name
For example, the configuration property `spring.main.log-startup-info` would be an environment variable named `SPRING_MAIN_LOGSTARTUPINFO`.
NOTE: Underscores cannot be used to replace the dashes in property names.
If you attempt to use `SPRING_MAIN_LOG_STARTUP_INFO` with the example above, no value will be bound.
Environment variables can also be used when binding to object lists.
To bind to a `List`, the element number should be surrounded with underscores in the variable name.
@@ -1461,7 +1458,7 @@ The following table summarizes the features that are supported by `@Configuratio
| <<boot-features-external-config-relaxed-binding,Relaxed binding>>
| Yes
| Limited (see note below)
| Limited (see <<boot-features-external-config-vs-value-note,note below>>)
| <<appendix-configuration-metadata.adoc#configuration-metadata,Meta-data support>>
| Yes
@@ -1472,15 +1469,15 @@ The following table summarizes the features that are supported by `@Configuratio
| Yes
|===
If you define a set of configuration keys for your own components, we recommend you group them in a POJO annotated with `@ConfigurationProperties`.
Doing so will provide you with structured, type-safe object that you can inject into your own beans.
If you do want to use `@Value`, we recommend that you refer to property names using their canonical form (kebab-case using only lowercase letters).
NOTE: [[boot-features-external-config-vs-value-note]] If you do want to use `@Value`, we recommend that you refer to property names using their canonical form (kebab-case using only lowercase letters).
This will allow Spring Boot to use the same logic as it does when relaxed binding `@ConfigurationProperties`.
For example, `@Value("{demo.item-price}")` will pick up `demo.item-price` and `demo.itemPrice` forms from the `application.properties` file, as well as `DEMO_ITEMPRICE` from the system environment.
If you used `@Value("{demo.itemPrice}")` instead, `demo.item-price` and `DEMO_ITEMPRICE` would not be considered.
Finally, while you can write a `SpEL` expression in `@Value`, such expressions are not processed from <<boot-features-external-config-application-property-files,application property files>>.
If you define a set of configuration keys for your own components, we recommend you group them in a POJO annotated with `@ConfigurationProperties`.
Doing so will provide you with structured, type-safe object that you can inject into your own beans.
While you can write a `SpEL` expression in `@Value`, such expressions are not processed from <<boot-features-external-config-application-property-files,application property files>>.