前言

最近在研究 srping cloud feign ，遇到了一个问题，就是当 get 请求的参数使用对象接收时，就会进入熔断返回。经过百度，发现网上大部分的解决方案都是将请求参数封装到RequestBody里面进行传输。但感觉这种方式并不怎么优雅。所以自己就研究了研究，以下是我给出的方案。有什么不对的地方还希望大家指正。

环境

java版本：8
spring cloud：Finchley.RELEASE

解决方案

1. 首先我们创建一个注解 GetParam ，用于将参数相关的信息封装到 RequestTemplate 。

import java.lang.annotation.*;

/**

 * Created by qingyun.yu on 2018/9/4.

 */

@Target({ElementType.PARAMETER})

@Retention(RetentionPolicy.RUNTIME)

@Documented

public @interface GetParam {

    Class value() default Object.class;

}

2. 创建注解处理器 GetParamParameterProcessor ，并且注册到spring容器中，主要逻辑是将参数相关信息封装到 Template 。

import feign.MethodMetadata;

import org.springframework.cloud.openfeign.AnnotatedParameterProcessor;

import org.springframework.stereotype.Component;

import java.lang.annotation.Annotation;

import java.lang.reflect.Field;

import java.lang.reflect.Method;

import java.util.Collection;

/**

 * Created by qingyun.yu on 2018/9/4.

 */

@Component

public class GetParamParameterProcessor implements AnnotatedParameterProcessor {

    private static final Class<GetParam> ANNOTATION = GetParam.class;

    @Override

    public Class<? extends Annotation> getAnnotationType() {

        return ANNOTATION;

    }

    @Override

    public boolean processArgument(AnnotatedParameterContext context, Annotation annotation, Method method) {

        int parameterIndex = context.getParameterIndex();

        Class parameterType = method.getParameterTypes()[parameterIndex];

        MethodMetadata data = context.getMethodMetadata();

        Field[] fields = parameterType.getDeclaredFields();

        for(Field field: fields) {

            String name = field.getName();

            context.setParameterName(name);

            Collection query = context.setTemplateParameter(name, (Collection)data.template().queries().get(name));

            data.template().query(name, query);

        }

        return true;

    }

}

3. 创建 FeignConfig ，用于将Spring的参数注解处理器注册到Spring中。

import org.springframework.cloud.openfeign.annotation.PathVariableParameterProcessor;

import org.springframework.cloud.openfeign.annotation.RequestHeaderParameterProcessor;

import org.springframework.cloud.openfeign.annotation.RequestParamParameterProcessor;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

/**

 * Created by qingyun.yu on 2018/9/4.

 */

@Configuration

public class FeignConfig {

    @Bean

    public PathVariableParameterProcessor getPathVariableParameterProcessor() {

        return new PathVariableParameterProcessor();

    }

    @Bean

    public RequestParamParameterProcessor getRequestParamParameterProcessor() {

        return new RequestParamParameterProcessor();

    }

    @Bean

    public RequestHeaderParameterProcessor getRequestHeaderParameterProcessor() {

        return new RequestHeaderParameterProcessor();

    }

}

4.修改 io.github.openfeign:feign-core 的源码，在 ReflectiveFeign 类中增加如下代码，源码地址点这里，也可以直接用我的demo里面的代码。

private boolean isGetUrlParam(Object value, RequestTemplate mutable) {

      if(mutable.method() != "GET") {

        return false;

      }

      switch (value.getClass().getSimpleName()) {

        case "Integer":

          return false;

        case "String":

          return false;

        case "Boolean":

          return false;

        case "Float":

          return false;

        case "Long":

          return false;

        case "Character":

          return false;

        case "Double":

          return false;

        case "Byte":

          return false;

        case "Short":

          return false;

        case "Date":

          return false;

        case "BigDecimal":

          return false;

        default:

          System.out.println("value is object param");;

      }

      return true;

    }

    private Map<String, Object> getObjectParam(Object obj) {

      Field[] fields = obj.getClass().getDeclaredFields();

      Map<String, Object> urlParams = new HashMap<>();

      for (Field field : fields) {

        field.setAccessible(true);

        try {

          Object value = field.get(obj);

          if (value == null) {

            urlParams.put(field.getName(), "");

          } else {

            urlParams.put(field.getName(), value);

          }

        } catch (Exception e) {

          throw new RuntimeException(e);

        }

      }

      return urlParams;

    }

并且将 RequestTemplate create(Object[] argv) 代码替换成如下代码。

@Override

    public RequestTemplate create(Object[] argv) {

      RequestTemplate mutable = new RequestTemplate(metadata.template());

      if (metadata.urlIndex() != null) {

        int urlIndex = metadata.urlIndex();

        checkArgument(argv[urlIndex] != null, "URI parameter %s was null", urlIndex);

        mutable.insert(0, String.valueOf(argv[urlIndex]));

      }

      Map<String, Object> varBuilder = new LinkedHashMap<String, Object>();

      for (Entry<Integer, Collection<String>> entry : metadata.indexToName().entrySet()) {

        int i = entry.getKey();

        Object value = argv[entry.getKey()];

        Map<String, Object> urlParams = null;

        if (isGetUrlParam(value, mutable)) {

          urlParams = getObjectParam(value);

        }

        if (value != null) { // Null values are skipped.

          if (indexToExpander.containsKey(i)) {

            value = expandElements(indexToExpander.get(i), value);

          }

          for (String name : entry.getValue()) {

            if (isGetUrlParam(value, mutable)) {

              varBuilder.put(name, urlParams.get(name));

            } else {

              varBuilder.put(name, value);

            }

          }

        }

      }

      RequestTemplate template = resolve(argv, mutable, varBuilder);

      if (metadata.queryMapIndex() != null) {

        // add query map parameters after initial resolve so that they take

        // precedence over any predefined values

        Object value = argv[metadata.queryMapIndex()];

        Map<String, Object> queryMap = toQueryMap(value);

        template = addQueryMapQueryParameters(queryMap, template);

      }

      if (metadata.headerMapIndex() != null) {

        template =

            addHeaderMapHeaders((Map<String, Object>) argv[metadata.headerMapIndex()], template);

      }

      return template;

    }

5. 编译打包 feign-core ，并且将其引入工程里面。

<dependency>

    <groupId>com.yun.demo</groupId>

    <artifactId>feign-core</artifactId>

    <version>1.0-SNAPSHOT</version>

</dependency>

注意要将spring cloud的原本引入的 feign-core 去除掉。

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
    <exclusions>
        <exclusion>
            <groupId>io.github.openfeign</groupId>
            <artifactId>feign-core</artifactId>
        </exclusion>
    </exclusions>
</dependency>

6. 使用时将注解注入到get请求的对象上就可以了。

import com.yun.demo.annotation.GetParam;

import com.yun.demo.entity.User;

import com.yun.demo.fallback.UserClientFallback;

import org.springframework.cloud.openfeign.FeignClient;

import org.springframework.web.bind.annotation.*;

/**

 * Created by qingyun.yu on 2018/9/2.

 */

@FeignClient(name = "feign-service", fallback = UserClientFallback.class)

public interface UserClient {

    @RequestMapping(value = "user", method = RequestMethod.GET)

    User getUser(@GetParam User user);

}

下面附上我的git地址，里面是我写的demo，有什么不妥的地方还希望各位大虾指正。

巴特西

[spring cloud feign] [bug] 使用对象传输get请求参数

前言

环境

解决方案

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