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There is a newer version: 8.18.0
/*
 * Copyright 2013 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.codec;

import feign.RequestTemplate;

import static java.lang.String.format;

/**
 * Encodes an object into an HTTP request body. Like {@code javax.websocket.Encoder}.
 * {@code Encoder} is used when a method parameter has no {@code @Param} annotation.
 * For example: 

 * 
 * 
 * @POST
 * @Path("/")
 * void create(User user);
 * 
 * Example implementation: 

 * 
 * 
 * public class GsonEncoder implements Encoder {
 *   private final Gson gson;
 *
 *   public GsonEncoder(Gson gson) {
 *     this.gson = gson;
 *   }
 *
 *   @Override
 *   public void encode(Object object, RequestTemplate template) {
 *     template.body(gson.toJson(object));
 *   }
 * }
 * 
 *
 * 
 * 
Form encoding
 * 

 * If any parameters are found in {@link feign.MethodMetadata#formParams()}, they will be
 * collected and passed to the Encoder as a {@code Map}.
 * 

 *  * @POST
 * @Path("/")
 * Session login(@Named("username") String username, @Named("password") String password);
 * 
 */
public interface Encoder {
  /**
   * Converts objects to an appropriate representation in the template.
   *
   * @param object what to encode as the request body.
   * @param template the request template to populate.
   * @throws EncodeException when encoding failed due to a checked exception.
   */
  void encode(Object object, RequestTemplate template) throws EncodeException;

  /**
   * Default implementation of {@code Encoder}.
   */
  public class Default implements Encoder {
    @Override
    public void encode(Object object, RequestTemplate template) throws EncodeException {
      if (object instanceof String) {
        template.body(object.toString());
      } else if (object instanceof byte[]) {
        template.body((byte[]) object, null);
      } else if (object != null) {
        throw new EncodeException(format("%s is not a type supported by this encoder.", object.getClass()));
      }
    }
  }
}