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/**
* Copyright 2012-2019 The Feign Authors
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License
* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
* or implied. See the License for the specific language governing permissions and limitations under
* the License.
*/
package feign;
import java.lang.annotation.Retention;
import java.util.List;
import java.util.Map;
import static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
/**
* A template parameter that can be applied to a Map that contains header
* entries, where the keys are Strings that are the header field names and the
* values are the header field values. The headers specified by the map will be
* applied to the request after all other processing, and will take precedence
* over any previously specified header parameters.
* This parameter is useful in cases where different header fields and values
* need to be set on an API method on a per-request basis in a thread-safe
* manner and independently of Feign client construction. A concrete example of
* a case like this are custom metadata header fields (e.g. as "x-amz-meta-*" or
* "x-goog-meta-*") where the header field names are dynamic and the range of
* keys cannot be determined a priori. The {@link Headers} annotation does not
* allow this because the header fields that it defines are static (it is not
* possible to add or remove fields on a per-request basis), and doing this
* using a custom {@link Target} or {@link RequestInterceptor} can be cumbersome
* (it requires more code for per-method customization, it is difficult to
* implement in a thread-safe manner and it requires customization when the
* Feign client for the API is built).
*
*
* ...
* @RequestLine("GET /servers/{serverId}")
* void get(@Param("serverId") String serverId, @HeaderMap Map);
* ...
*
*
* The annotated parameter must be an instance of {@link Map}, and the keys must
* be Strings. The header field value of a key will be the value of its toString
* method, except in the following cases:
*
*
* - if the value is null, the value will remain null (rather than converting
* to the String "null")
*
- if the value is an {@link Iterable}, it is converted to a {@link List} of
* String objects where each value in the list is either null if the original
* value was null or the value's toString representation otherwise.
*
*
* Once this conversion is applied, the query keys and resulting String values
* follow the same contract as if they were set using
* {@link RequestTemplate#header(String, String...)}.
*/
@Retention(RUNTIME)
@java.lang.annotation.Target(PARAMETER)
public @interface HeaderMap {
}