#MidServerClient.java
import feign.Param;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
@FeignClient(value = "edu-mid-server")
public interface MidServerClient {
    @RequestMapping(value = "/test/header", method = RequestMethod.GET)
    @Headers({"userInfo:{userInfo}"})
    Object headerTest(@Param("userInfo") String userInfo);
}

java.lang.IllegalArgumentException: method GET must not have a request body.

@Configuration
public class FeignClientsConfiguration {
	@Bean
	@ConditionalOnMissingBean
	public Contract feignContract(ConversionService feignConversionService) {
		return new SpringMvcContract(this.parameterProcessors, feignConversionService);
	}

#FeignCustomContract.java
import feign.Headers;
import feign.MethodMetadata;
import feign.Param;
import org.springframework.cloud.openfeign.AnnotatedParameterProcessor;
import org.springframework.cloud.openfeign.support.SpringMvcContract;
import org.springframework.core.convert.ConversionService;
import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.*;
import static feign.Util.checkState;
import static feign.Util.emptyToNull;
public class FeignCustomContract extends SpringMvcContract {
    public FeignCustomContract(List<AnnotatedParameterProcessor> annotatedParameterProcessors, ConversionService conversionService) {
        super(annotatedParameterProcessors, conversionService);
    }
    @Override
    protected void processAnnotationOnMethod(MethodMetadata data, Annotation methodAnnotation, Method method) {
        //解析mvc的注解
        super.processAnnotationOnMethod(data, methodAnnotation, method);
        //解析feign的headers注解
        Class<? extends Annotation> annotationType = methodAnnotation.annotationType();
        if (annotationType == Headers.class) {
            String[] headersOnMethod = Headers.class.cast(methodAnnotation).value();
            checkState(headersOnMethod.length > 0, "Headers annotation was empty on method %s.", method.getName());
            data.template().headers(toMap(headersOnMethod));
        }
    }
    @Override
    protected boolean processAnnotationsOnParameter(MethodMetadata data, Annotation[] annotations, int paramIndex) {
        boolean isMvcHttpAnnotation = super.processAnnotationsOnParameter(data, annotations, paramIndex);
        boolean isFeignHttpAnnotation = false;
        for (Annotation annotation : annotations) {
            Class<? extends Annotation> annotationType = annotation.annotationType();
            if (annotationType == Param.class) {
                Param paramAnnotation = (Param) annotation;
                String name = paramAnnotation.value();
                checkState(emptyToNull(name) != null, "Param annotation was empty on param %s.", paramIndex);
                nameParam(data, name, paramIndex);
                isFeignHttpAnnotation = true;
                if (!data.template().hasRequestVariable(name)) {
                    data.formParams().add(name);
                }
            }
        }
        return isMvcHttpAnnotation || isFeignHttpAnnotation;
    }
    private static Map<String, Collection<String>> toMap(String[] input) {
        Map<String, Collection<String>> result =
                new LinkedHashMap<String, Collection<String>>(input.length);
        for (String header : input) {
            int colon = header.indexOf(':');
            String name = header.substring(0, colon);
            if (!result.containsKey(name)) {
                result.put(name, new ArrayList<String>(1));
            }
            result.get(name).add(header.substring(colon + 1).trim());
        }
        return result;
    }
}

#FeignCustomConfiguration.java
import feign.Contract;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.cloud.openfeign.AnnotatedParameterProcessor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.convert.ConversionService;
import java.util.ArrayList;
import java.util.List;
@Configuration
public class FeignCustomConfiguration {
    @Autowired(required = false)
    private List<AnnotatedParameterProcessor> parameterProcessors = new ArrayList<>();
    @Bean
    @ConditionalOnProperty(name = "feign.feign-custom-contract", havingValue = "true", matchIfMissing = true)
    public Contract feignContract(ConversionService feignConversionService) {
        return new FeignCustomContract(this.parameterProcessors, feignConversionService);
    }