feign client请求参数用json，响应参数接收protobuf

可以通过Feign的`@RequestBody`注解将请求参数转换为JSON格式，同时通过定义`@Headers`注解设置请求的`Content-Type`为`application/json`。然后在定义Feign接口时，可以使用`@Headers`注解定义接收响应的`Content-Type`为`application/protobuf`，并且使用`@ResponseParser`注解指定响应解析器为Protobuf格式。示例代码如下：

import feign.Headers;
import feign.Param;
import feign.RequestLine;
import feign.Response;
import feign.codec.Decoder;
import feign.codec.Encoder;
import feign.codec.ErrorDecoder;
import feign.protobuf.ProtobufDecoder;
import feign.protobuf.ProtobufEncoder;
import feign.slf4j.Slf4jLogger;

public interface MyService {

    @RequestLine("POST /api")
    @Headers({"Content-Type: application/json"})
    @ResponseParser(ProtobufResponseParser.class)
    MyResponse postJson(@RequestBody MyRequest request);

    static class ProtobufResponseParser implements ResponseParser {
        private final ProtobufDecoder decoder = new ProtobufDecoder(MyResponse.class);

        @Override
        public Object parseResponse(Response response) throws IOException {
            return decoder.decode(response, MyResponse.class);
        }
    }

    static MyService connect(String url) {
        return Feign.builder()
                .logger(new Slf4jLogger())
                .encoder(new ProtobufEncoder())
                .decoder(new ProtobufDecoder())
                .errorDecoder(new MyErrorDecoder())
                .target(MyService.class, url);
    }
}

注意：这里假设`MyRequest`和`MyResponse`分别是请求和响应的Java对象，且`MyResponse`是Protobuf格式的。同时需要定义一个`ProtobufResponseParser`类，用于将响应转换为Java对象。在`Feign.builder()`中需要设置`encoder`和`decoder`为`ProtobufEncoder`和`ProtobufDecoder`，并且还需要定义一个错误解码器`MyErrorDecoder`，用于处理HTTP请求失败时的异常情况。