Spring Cloud OpenFeign

apan 3/2/2024 spring后端

# 简介

简化外部调用官方文档：https://docs.spring.io/spring-cloud-openfeign/docs/current/reference/html/

# 使用

依赖

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
    <version>2.2.10.RELEASE</version>
</dependency>

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启动类加注解

@SpringBootApplication
@EnableFeignClients
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

}

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业务代码

@FeignClient(name = "${feign.name}", url = "${feign.url}", configuration = FooConfiguration.class)
public interface StoreClient {
    @RequestMapping(method = RequestMethod.GET, value = "/stores")
    List<Store> getStores();

    @RequestMapping(method = RequestMethod.GET, value = "/stores")
    Page<Store> getStores(Pageable pageable);

    @RequestMapping(method = RequestMethod.POST, value = "/stores/{storeId}", consumes = "application/json")
    Store update(@PathVariable("storeId") Long storeId, Store store);

    @RequestMapping(method = RequestMethod.DELETE, value = "/stores/{storeId:\\d+}")
    void delete(@PathVariable Long storeId);
}

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可以配置自动获取token等

# 注意

配置类上不需要加@Configuration注解
配置url后也需要配置name
拦截器上如果添加了@Configuration注解，会全局生效，所有的feign调用都会走这个拦截器！！

# 关键类

feign.SynchronousMethodHandler

# 查看拦截器

尤其是老项目，有大量拦截器，可能会修改入参导致不能调通接口

Request targetRequest(RequestTemplate template) {  
  for (RequestInterceptor interceptor : requestInterceptors) {  
    interceptor.apply(template);  
  }  
  return target.apply(template);  
}

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# 查看实际请求

断点调试

response = client.execute(request, options);

# 常见问题

# 找不到bean

原因：有些老项目包路径不规范，maven分模块项目报名不一致方法如下：

指定扫码路径 @EnableFeignClients(basePackages = "com.example.clients")
指定FeignClient类 @EnableFeignClients(clients = InventoryServiceFeignClient.class)

# 收不到值

原因：java的框架属性都是首字母小写的，有些外部系统字段首字母大写就不认了解决方法：实体类属性上加注解@JsonProperty("Response")

# pathVariable urlencode的内容被decode

@FeignClient(name = "yourClient", url= "xxxx", configuration = YourClient.ClientConf.class)
public interface YourClient {
  class ClientConf{
     @Bean
          Contract contract(@Autowired(required = false) List<AnnotatedParameterProcessor> parameterProcessors,
                            ConversionService feignConversionService) {
              if (parameterProcessors == null) {
                  parameterProcessors = new ArrayList<>();
              }
              return new SpringMvcContract(parameterProcessors, feignConversionService, false);
          }
   }
}

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