本文小编为大家详细介绍“SpringCloud项目中Feign组件添加请求头所遇到的坑如何解决”，内容详细，步骤清晰，细节处理妥当，希望这篇“SpringCloud项目中Feign组件添加请求头所遇到的坑如何解决”文章能帮助大家解决疑惑，下面跟着小编的思路慢慢深入，一起来学习新知识吧。
前言
在spring cloud的项目中用到了feign组件，简单配置过后即可完成请求的调用。
又因为有向请求添加Header头的需求，查阅了官方示例后，就觉得很简单，然后一顿操作之后调试报错...
按官方修改的示例：
#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);
}提示错误：
java.lang.IllegalArgumentException: method GET must not have a request body.
分析
通过断点debug发现feign发请求时把userInfo参数当成了requestBody来处理，而okhttp3会检测get请求不允许有body（其他类型的请求哪怕不报错，但因为不是设置到请求头，依然不满足需求）。
查阅官方文档里是通过Contract（Feign.Contract.Default）来解析注解的：
Feign annotations define the Contract between the interface and how the underlying client should work. Feign's default contract defines the following annotations:
| Annotation | Interface Target | Usage |
|---|---|---|
| @RequestLine | Method | Defines the HttpMethod and UriTemplate for request. Expressions, values wrapped in curly-braces {expression} are resolved using their corresponding @Param annotated parameters. |
| @Param | Parameter | Defines a template variable, whose value will be used to resolve the corresponding template Expression, by name. |
| @Headers | Method, Type | Defines a HeaderTemplate; a variation on a UriTemplate. that uses @Param annotated values to resolve the corresponding Expressions. When used on a Type, the template will be applied to every request. When used on a Method, the template will apply only to the annotated method. |
| @QueryMap | Parameter | Defines a Map of name-value pairs, or POJO, to expand into a query string. |
| @HeaderMap | Parameter | Defines a Map of name-value pairs, to expand into Http Headers |
| @Body | Method | Defines a Template, similar to a UriTemplate and HeaderTemplate, that uses @Param annotated values to resolve the corresponding Expressions. |
从自动配置类找到使用的是spring cloud的SpringMvcContract（用来解析@RequestMapping相关的注解）,而这个注解并不会处理解析上面列的注解
@Configuration
public class FeignClientsConfiguration {
···
@Bean
@ConditionalOnMissingBean
public Contract feignContract(ConversionService feignConversionService) {
return new SpringMvcContract(this.parameterProcessors, feignConversionService);
}
···解决
原因找到了
spring cloud使用了自己的SpringMvcContract来解析注解，导致默认的注解解析方式失效。
解决方案自然就是重新解析处理feign的注解，这里通过自定义Contract继承SpringMvcContract再把Feign.Contract.Default解析逻辑般过来即可（重载的方法是在SpringMvcContract基础上做进一步解析，否则Feign对RequestMapping相关对注解解析会失效）
代码如下(此处只对@Headers、@Param重新做了解析)：
#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);
}
···改完马上进行新一顿的操作, 看请求日志已经设置成功，响应OK！:
请求：{"type":"OKHTTP_REQ","uri":"/test/header","httpMethod":"GET","header":"{"accept":["/"],"userinfo":["{"userId":"sssss","phone":"13544445678],"x-b3-parentspanid":["e49c55484f6c19af"],"x-b3-sampled":["0"],"x-b3-spanid":["1d131b4ccd08d964"],"x-b3-traceid":["9405ce71a13d8289"]}","param":""}
响应{"type":"OKHTTP_RESP","uri":"/test/header","respStatus":0,"status":200,"time":5,"header":"{"cache-control":["no-cache,no-store,max-age=0,must-revalidate"],"connection":["keep-alive"],"content-length":["191"],"content-type":["application/json;charset=UTF-8"],"date":["Fri,11Oct201913:02:41GMT"],"expires":["0"],"pragma":["no-cache"],"x-content-type-options":["nosniff"],"x-frame-options":["DENY"],"x-xss-protection":["1;mode=block"]}"}