SpringCloud @FeignClient参数的用法解析

SpringCloud @FeignClient 参数详解

今天因为工作中遇到FeignClient一个奇葩的bug，后面仔细研究了，找出了原因，那么刚好对FeignClient 这个注解总结一下：

先看@FeignClient 源码：源码如下，本文最后面。

11个方法，常用方法说明如下

@FeignClient(name = "service-name", url = "${feign.urls.service-name:}", fallback =ApiFallBack.class,configuration = Interceptor.class)

• 1.value,name 这两个就同一个意思：对应的是调用的微服务的服务名，对用服务发现、走网关调用，这个很关键。

• 2.url 这是访问地址，可以直接提供给外部调用，也可以直接写如192.168.1.11:8800/applicationName

• 3.fallback 与fallbackFactory

就给@FeignClient注解设置fallback属性，并且回退类要继承@FeignClient所注解的接口

ApiFallBack类拿出去单独作为一个类的话，我们就得在该类上添加注解@Component

如果fallback默认优先级比fallfactory优先级高。所以二者都存在的话，会访问fallback的回退方法。

这里不做演示。

那么fallback和fallfactory有什么区别呢

@FeignClient(name = "service-name", fallbackFactory = HystrixClientFallbackFactory.class)
protected interface HystrixClient {
@RequestMapping(method = RequestMethod.GET, value = "/test")
          Hello iFailSometimes();
}
@Component
static class HystrixClientFallbackFactory implements FallbackFactory<HystrixClient> {
@Override
public HystrixClient create(Throwable cause) {
return new HystrixClientWithFallBackFactory() {
@Override
public Hello iFailSometimes() {
return new Hello("fallback; reason was: " + cause.getMessage());
}
};
}
}

fallback和fallfactory区别

• fallback 只是重写了回退方法。

• fallfactory 层面比较深，因为它用线程抛出了异常,可以看到底层具体问题。

/**
* Annotation for interfaces declaring that a REST client with that interface should be
* created (e.g. for autowiring into another component). If ribbon is available it will be
* used to load balance the backend requests, and the load balancer can be configured
* using a <code>@RibbonClient</code> with the same name (i.e. value) as the feign client.
*
* @author Spencer Gibb
* @author Venil Noronha
*/
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface FeignClient {

/**
   * The name of the service with optional protocol prefix. Synonym for {@link #name()
   * name}. A name must be specified for all clients, whether or not a url is provided.
   * Can be specified as property key, eg: ${propertyKey}.
   */
  @AliasFor("name")
  String value() default "";

/**
   * The service id with optional protocol prefix. Synonym for {@link #value() value}.
   *
   * @deprecated use {@link #name() name} instead
   */
  @Deprecated
  String serviceId() default "";

/**
   * The service id with optional protocol prefix. Synonym for {@link #value() value}.
   */
  @AliasFor("value")
  String name() default "";

/**
   * Sets the <code>@Qualifier</code> value for the feign client.
   */
  String qualifier() default "";

/**
   * An absolute URL or resolvable hostname (the protocol is optional).
   */
  String url() default "";

/**
   * Whether 404s should be decoded instead of throwing FeignExceptions
   */
  boolean decode404() default false;

/**
   * A custom <code>@Configuration</code> for the feign client. Can contain override
   * <code>@Bean</code> definition for the pieces that make up the client, for instance
   * {@link feign.codec.Decoder}, {@link feign.codec.Encoder}, {@link feign.Contract}.
   *
   * @see FeignClientsConfiguration for the defaults
   */
  Class<?>[] configuration() default {};

/**
   * Fallback class for the specified Feign client interface. The fallback class must
   * implement the interface annotated by this annotation and be a valid spring bean.
   */
  Class<?> fallback() default void.class;

/**
   * Define a fallback factory for the specified Feign client interface. The fallback
   * factory must produce instances of fallback classes that implement the interface
   * annotated by {@link FeignClient}. The fallback factory must be a valid spring
   * bean.
   *
   * @see feign.hystrix.FallbackFactory for details.
   */
  Class<?> fallbackFactory() default void.class;

/**
   * Path prefix to be used by all method-level mappings. Can be used with or without
   * <code>@RibbonClient</code>.
   */
  String path() default "";

/**
   * Whether to mark the feign proxy as a primary bean. Defaults to true.
   */
  boolean primary() default true;

}

@FeignClient 注解常用参数

怕以后又忘记，总结下目前项目中实际用到的 @FeignClient 注解中的参数，如下：

@FeignClient(value = "annoroad-alpha",  url = "${annoroad.ms.annoroad-alpha.url}")
public interface UserFacade {
   @PostMapping(value = "/user/detail")
   UserDto detail(@RequestParam("id") long id);
}

value

• value 等同于 name

url

• 一般用于调试，可以手动指定 @FeignClient 调用的地址

来源：https://blog.csdn.net/Susan8888/article/details/95992172