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/*
 * Copyright 2015 Netflix, Inc.
 *
 * 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 static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

/** A named template parameter applied to {@link Headers}, {@linkplain RequestLine} or {@linkplain Body} */
@Retention(RUNTIME)
@java.lang.annotation.Target(PARAMETER)
public @interface Param {
  /** The name of the template parameter. */
  String value();

  /** How to expand the value of this parameter, if {@link ToStringExpander} isn't adequate. */
  Class expander() default ToStringExpander.class;

  interface Expander {
    /** Expands the value into a string. Does not accept or return null. */
    String expand(Object value);
  }

  final class ToStringExpander implements Expander {
    @Override public String expand(Object value) {
      return value.toString();
    }
  }
}