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Document @ConstructorBinding and @DefaultValue with records

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Closes gh-30460
This commit is contained in:
Andy Wilkinson
2022-03-29 14:14:28 +01:00
parent 24e748d5cd
commit d574563616
5 changed files with 129 additions and 6 deletions
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7
spring-boot-project/spring-boot-docs/src/docs/asciidoc/features/external-config.adoc
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@@ -721,11 +721,14 @@ include::{docs-java}/features/externalconfig/typesafeconfigurationproperties/con
In this setup, the `@ConstructorBinding` annotation is used to indicate that constructor binding should be used.
This means that the binder will expect to find a constructor with the parameters that you wish to have bound.
If you are using Java 16 or later, constructor binding can be used with records.
Nested members of a `@ConstructorBinding` class (such as `Security` in the example above) will also be bound via their constructor.
Default values can be specified using `@DefaultValue` and the same conversion service will be applied to coerce the `String` value to the target type of a missing property.
By default, if no properties are bound to `Security`, the `MyProperties` instance will contain a `null` value for `security`.
Default values can be specified using `@DefaultValue` on a constructor parameter or, when using Java 16 or later, a record component.
The conversion service will be applied to coerce the `String` value to the target type of a missing property.
Referring to the previous example, if no properties are bound to `Security`, the `MyProperties` instance will contain a `null` value for `security`.
If you wish you return a non-null instance of `Security` even when no properties are bound to it, you can use an empty `@DefaultValue` annotation to do so:
[source,java,indent=0,subs="verbatim"]