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This version is still in development and is not considered stable yet. For the latest stable version, please use Spring Framework 6.2.0! |
Annotations
The Spring Framework also takes advantage of Kotlin null-safety
to determine if an HTTP parameter is required without having to explicitly
define the required attribute. That means @RequestParam name: String? is treated
as not required and, conversely, @RequestParam name: String is treated as being required.
This feature is also supported on the Spring Messaging @Header annotation.
In a similar fashion, Spring bean injection with @Autowired, @Bean, or @Inject uses
this information to determine if a bean is required or not.
For example, @Autowired lateinit var thing: Thing implies that a bean
of type Thing must be registered in the application context, while @Autowired lateinit var thing: Thing?
does not raise an error if such a bean does not exist.
Following the same principle, @Bean fun play(toy: Toy, car: Car?) = Baz(toy, Car) implies
that a bean of type Toy must be registered in the application context, while a bean of
type Car may or may not exist. The same behavior applies to autowired constructor parameters.
If you use bean validation on classes with properties or a primary constructor
parameters, you may need to use
annotation use-site targets,
such as @field:NotNull or @get:Size(min=5, max=15), as described in
this Stack Overflow response.
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