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// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
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package org.apache.juneau.http.annotation;

import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.RetentionPolicy.*;

import java.lang.annotation.*;

import org.apache.juneau.annotation.*;
import org.apache.juneau.httppart.*;
import org.apache.juneau.oapi.*;

/**
 * REST request header annotation.
 *
 * 
 * Identifies a POJO to be used as the header of an HTTP request.
 *
 * 

 * Can be used in the following locations:
 * 

 * 	Arguments and argument-types of server-side @RestOp-annotated methods.
 * 	
Arguments and argument-types of client-side @RemoteResource-annotated interfaces.
 * 	
Methods and return types of server-side and client-side @Request-annotated interfaces.
 * 
 *
 * Arguments and argument-types of server-side @RestOp-annotated methods
 * 
 * Annotation that can be applied to a parameter of a @RestOp-annotated method to identify it as a HTTP
 * request header.
 *
 * 
Example:
 * 
 * 	@RestGet
 * 	public void doGet(@Header("ETag") UUID etag) {...}
 * 
 *
 * 
 * This is functionally equivalent to the following code...
 * 

 * 	@RestGet
 * 	public void doGet(RestRequest req, RestResponse res) {
 * 		UUID etag = req.getHeader("ETag").as(UUID.class).orElse(null);
 * 		...
 * 	}
 * 
 *
 * See Also:

 * 	Swagger
 * 	
Swagger Parameter Object
 * 
 *
 * Arguments and argument-types of client-side @RemoteResource-annotated interfaces
 * 
 * Annotation applied to Java method arguments of interface proxies to denote that they are serialized as an HTTP
 * header value.
 *
 * 
See Also:

 * 	@Header
 * 
 *
 * Methods and return types of server-side and client-side @Request-annotated interfaces
 * 
 * 
See Also:

 * 	@Request
 * 
 * 
 * 
See Also:


 * 
 */
@Documented
@Target({PARAMETER,METHOD,TYPE,FIELD})
@Retention(RUNTIME)
@Inherited
@Repeatable(HeaderAnnotation.Array.class)
@ContextApply(HeaderAnnotation.Applier.class)
public @interface Header {

	/**
	 * Default value for this parameter.
	 *
	 * @return The annotation value.
	 */
	String def() default "";

	/**
	 * HTTP header name.
	 * 
	 * A blank value (the default) indicates to reuse the bean property name when used on a request bean property.
	 *
	 * 

	 * The value should be either a valid HTTP header name, or "*" to represent multiple name/value pairs
	 *
	 * 

	 * A blank value (the default) has the following behavior:
	 * 

	 * 	
	 * 		If the data type is NameValuePairs, Map, or a bean,
	 * 		then it's the equivalent to "*" which will cause the value to be serialized as name/value pairs.
	 *
	 * 		Examples:
	 * 		
	 * 	// When used on a REST method
	 * 	@RestPost("/addPet")
	 * 	public void addPet(@Header JsonMap allHeaderParameters) {...}
	 * 		
	 * 		
	 * 	// When used on a remote method parameter
	 * 	@RemoteResource(path="/myproxy")
	 * 	public interface MyProxy {
	 *
	 * 		// Equivalent to @Header("*")
	 * 		@RemoteGet("/mymethod")
	 * 		String myProxyMethod1(@Header Map<String,Object> allHeaderParameters);
	 * 	}
	 * 		
	 * 		
	 * 	// When used on a request bean method
	 * 	public interface MyRequest {
	 *
	 * 		// Equivalent to @Header("*")
	 * 		@Header
	 * 		Map<String,Object> getFoo();
	 * 	}
	 * 		
	 * 	
	 * 	
	 * 		If used on a request bean method, uses the bean property name.
	 *
	 * 		Example:
	 * 		
	 * 	public interface MyRequest {
	 *
	 * 		// Equivalent to @Header("Foo")
	 * 		@Header
	 * 		@Beanp("Foo")
	 * 		String getFoo();
	 * 	}
	 * 		
	 * 	
	 * 
	 *
	 * @return The annotation value.
	 */
	String name() default "";

	/**
	 * Dynamically apply this annotation to the specified classes.
	 *
	 * See Also:

	 * 	Dynamically Applied Annotations
	 * 
	 *
	 * @return The annotation value.
	 */
	String[] on() default {};

	/**
	 * Dynamically apply this annotation to the specified classes.
	 *
	 * 
	 * Identical to {@link #on()} except allows you to specify class objects instead of a strings.
	 *
	 * 
See Also:

	 * 	Dynamically Applied Annotations
	 * 
	 *
	 * @return The annotation value.
	 */
	Class[] onClass() default {};

	/**
	 * Specifies the {@link HttpPartParser} class used for parsing strings to values.
	 *
	 * 
	 * Overrides for this part the part parser defined on the REST resource which by default is {@link OpenApiParser}.
	 *
	 * @return The annotation value.
	 */
	Class parser() default HttpPartParser.Void.class;

	/**
	 * schema field of the Swagger Parameter Object.
	 *
	 * 

	 * The schema defining the type used for parameter.
	 *
	 * 

	 * The {@link Schema @Schema} annotation can also be used standalone on the parameter or type.
	 * Values specified on this field override values specified on the type, and values specified on child types override values
	 * specified on parent types.
	 *
	 * 
Used for:
	 * 
	 * 	
	 * 		Server-side schema-based parsing and parsing validation.
	 * 	

	 * 		Server-side generated Swagger documentation.
	 * 	

	 * 		Client-side schema-based serializing and serializing validation.
	 * 
	 *
	 * @return The annotation value.
	 */
	Schema schema() default @Schema;

	/**
	 * Specifies the {@link HttpPartSerializer} class used for serializing values to strings.
	 *
	 * 
	 * Overrides for this part the part serializer defined on the REST client which by default is {@link OpenApiSerializer}.
	 *
	 * @return The annotation value.
	 */
	Class serializer() default HttpPartSerializer.Void.class;

	/**
	 * A synonym for {@link #name()}.
	 *
	 * 

	 * Allows you to use shortened notation if you're only specifying the name.
	 *
	 * 

	 * The following are completely equivalent ways of defining a header entry:
	 * 

	 * 	public Order placeOrder(@Header(name="api_key") String apiKey) {...}
	 * 
	 * 
	 * 	public Order placeOrder(@Header("api_key") String apiKey) {...}
	 * 
	 *
	 * @return The annotation value.
	 */
	String value() default "";
}