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update RequestHeader reference and documentation
Signed-off-by: zakaria-shahen <[email protected]>
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‎framework-docs/modules/ROOT/pages/web/webflux/controller/ann-methods/requestheader.adoc‎

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@@ -63,3 +63,60 @@ TIP: Built-in support is available for converting a comma-separated string into
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array or collection of strings or other types known to the type conversion system. For
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example, a method parameter annotated with `@RequestHeader("Accept")` may be of type
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`String` but also of `String[]` or `List<String>`.
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We can further remove our dependency on Spring Web MVC by making `@RequestHeader` a meta-annotation on our own annotation. The next example demonstrates how we could do so on an annotation named `@LanguageRequestHeader`.
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[tabs]
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======
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Java::
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[source,java,indent=0,subs="verbatim,quotes"]
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----
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@Target({ElementType.PARAMETER, ElementType.TYPE})
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@Retention(RetentionPolicy.RUNTIME)
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@Documented
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@RequestHeader(value = HttpHeaders.ACCEPT_LANGUAGE, defaultValue = "en")
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public @interface LanguageRequestHeader {}
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----
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Kotlin::
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[source,kotlin,indent=0,subs="verbatim,quotes"]
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----
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@Target(AnnotationTarget.VALUE_PARAMETER, AnnotationTarget.TYPE)
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@Retention(AnnotationRetention.RUNTIME)
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@MustBeDocumented
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@RequestHeader(value = HttpHeaders.ACCEPT_LANGUAGE, defaultValue = "en")
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annotation class LanguageRequestHeader
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----
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======
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We have isolated our dependency on Spring MVC to a single file. Now that `@LanguageRequestHeader` has been specified, we can use it to signal to resolve our LanguageRequestHeader of the currently `Accept-Language` request header:
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[tabs]
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======
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Java::
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[source,java,indent=0,subs="verbatim,quotes"]
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----
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@GetMapping("/product")
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public Flux<Product> fetchProduct(@LanguageRequestHeader String lang) {
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// .. fetch product and return them ...
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}
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----
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Kotlin::
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+
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[source,kotlin,indent=0,subs="verbatim,quotes"]
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----
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@GetMapping("/product")
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fun fetchProduct(@LanguageRequestHeader lang: String): Flux<Product> {
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// .. fetch product and return them ...
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}
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----
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======
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TIP: We can replace the lang parameter type from `String` to `java.util.Locale` or to our own Language enum, and Spring will handle the conversion of the header value.

‎framework-docs/modules/ROOT/pages/web/webmvc/mvc-controller/ann-methods/requestheader.adoc‎

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Original file line numberDiff line numberDiff line change
@@ -63,3 +63,60 @@ TIP: Built-in support is available for converting a comma-separated string into
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array or collection of strings or other types known to the type conversion system. For
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example, a method parameter annotated with `@RequestHeader("Accept")` can be of type
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`String` but also `String[]` or `List<String>`.
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We can further remove our dependency on Spring Web MVC by making `@RequestHeader` a meta-annotation on our own annotation. The next example demonstrates how we could do so on an annotation named `@LanguageRequestHeader`.
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[tabs]
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======
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Java::
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+
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[source,java,indent=0,subs="verbatim,quotes"]
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----
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@Target({ElementType.PARAMETER, ElementType.TYPE})
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@Retention(RetentionPolicy.RUNTIME)
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@Documented
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@RequestHeader(value = HttpHeaders.ACCEPT_LANGUAGE, defaultValue = "en")
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public @interface LanguageRequestHeader {}
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----
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Kotlin::
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+
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[source,kotlin,indent=0,subs="verbatim,quotes"]
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----
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@Target(AnnotationTarget.VALUE_PARAMETER, AnnotationTarget.TYPE)
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@Retention(AnnotationRetention.RUNTIME)
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@MustBeDocumented
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@RequestHeader(value = HttpHeaders.ACCEPT_LANGUAGE, defaultValue = "en")
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annotation class LanguageRequestHeader
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----
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======
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We have isolated our dependency on Spring MVC to a single file. Now that `@LanguageRequestHeader` has been specified, we can use it to signal to resolve our LanguageRequestHeader of the currently `Accept-Language` request header:
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[tabs]
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======
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Java::
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+
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[source,java,indent=0,subs="verbatim,quotes"]
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----
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@GetMapping("/product")
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public List<Product> fetchProduct(@LanguageRequestHeader String lang) {
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// .. fetch product and return them ...
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}
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----
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Kotlin::
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+
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[source,kotlin,indent=0,subs="verbatim,quotes"]
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----
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@GetMapping("/product")
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fun fetchProduct(@LanguageRequestHeader lang: String): List<Product> {
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// .. fetch product and return them ...
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}
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----
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======
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TIP: We can replace the lang parameter type from `String` to `java.util.Locale` or to our own Language enum, and Spring will handle the conversion of the header value.

‎spring-web/src/main/java/org/springframework/web/bind/annotation/RequestHeader.java‎

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/**
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* Annotation which indicates that a method parameter should be bound to a web request header.
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*
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* <p>Supported for annotated handler methods in Spring MVC and Spring WebFlux.
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* <p>Supported for declared as a meta-annotation or directly annotated handler methods
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* in Spring MVC and Spring WebFlux.
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*
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* <p>If the method parameter is {@link java.util.Map Map&lt;String, String&gt;},
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* {@link org.springframework.util.MultiValueMap MultiValueMap&lt;String, String&gt;},
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*
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* @author Juergen Hoeller
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* @author Sam Brannen
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* @author Zakaria Shahen
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* @since 3.0
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* @see RequestMapping
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* @see RequestParam

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