SpringCloud @FeignClient參數的用法解析
SpringCloud @FeignClient 參數詳解
今天因為工作中遇到FeignClient一個奇葩的bug,後面仔細研究瞭,找出瞭原因,那麼剛好對FeignClient 這個註解總結一下:
先看@FeignClient 源碼:源碼如下,本文最後面。
11個方法,常用方法說明如下
@FeignClient(name = "service-name", url = "${feign.urls.service-name:}", fallback =ApiFallBack.class,configuration = Interceptor.class)
- 1.
value
,name
這兩個就同一個意思:對應的是調用的微服務的服務名,對用服務發現、走網關調用,這個很關鍵。 - 2.
url
這是訪問地址,可以直接提供給外部調用,也可以直接寫如192.168.1.11:8800/applicationName - 3.
fallback
與fallbackFactory
就給@FeignClient註解設置fallback屬性,並且回退類要繼承@FeignClient所註解的接口
ApiFallBack類拿出去單獨作為一個類的話,我們就得在該類上添加註解@Component
如果fallback默認優先級比fallfactory優先級高。所以二者都存在的話,會訪問fallback的回退方法。
這裡不做演示。
那麼fallback和fallfactory有什麼區別呢
@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區別
fallback
隻是重寫瞭回退方法。fallfactory
層面比較深,因為它用線程拋出瞭異常,可以看到底層具體問題。
/** * 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: ${propertyKey}. */ @AliasFor("name") String value() default ""; /** * The service id with optional protocol prefix. Synonym for {@link #value() value}. * * @deprecated use {@link #name() name} instead */ @Deprecated String serviceId() default ""; /** * The service id with optional protocol prefix. Synonym for {@link #value() value}. */ @AliasFor("value") String name() default ""; /** * Sets the <code>@Qualifier</code> value for the feign client. */ String qualifier() default ""; /** * An absolute URL or resolvable hostname (the protocol is optional). */ String url() default ""; /** * Whether 404s should be decoded instead of throwing FeignExceptions */ boolean decode404() default false; /** * A custom <code>@Configuration</code> for the feign client. Can contain override * <code>@Bean</code> definition for the pieces that make up the client, for instance * {@link feign.codec.Decoder}, {@link feign.codec.Encoder}, {@link feign.Contract}. * * @see FeignClientsConfiguration for the defaults */ Class<?>[] configuration() default {}; /** * Fallback class for the specified Feign client interface. The fallback class must * implement the interface annotated by this annotation and be a valid spring bean. */ Class<?> fallback() default void.class; /** * Define a fallback factory for the specified Feign client interface. The fallback * factory must produce instances of fallback classes that implement the interface * annotated by {@link FeignClient}. The fallback factory must be a valid spring * bean. * * @see feign.hystrix.FallbackFactory for details. */ Class<?> fallbackFactory() default void.class; /** * Path prefix to be used by all method-level mappings. Can be used with or without * <code>@RibbonClient</code>. */ String path() default ""; /** * Whether to mark the feign proxy as a primary bean. Defaults to true. */ boolean primary() default true; }
@FeignClient 註解常用參數
怕以後又忘記,總結下目前項目中實際用到的 @FeignClient 註解中的參數,如下:
@FeignClient(value = "annoroad-alpha", url = "${annoroad.ms.annoroad-alpha.url}") public interface UserFacade { @PostMapping(value = "/user/detail") UserDto detail(@RequestParam("id") long id); }
value
- value 等同於 name
url
- 一般用於調試,可以手動指定 @FeignClient 調用的地址
以上為個人經驗,希望能給大傢一個參考,也希望大傢多多支持WalkonNet。
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