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本篇文章为大家展示了如何解析SpringCloud @FeignClient参数的用法,内容简明扼要并且容易理解,绝对能使你眼前一亮,通过这篇文章的详细介绍希望你能有所收获。
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: ${propertyKey}. */ @AliasFor("name") String value() default ""; /** * The service id with optional protocol prefix. Synonym for {@link #value() value}. * * @deprecated use {@link #name() name} instead */ @Deprecated String serviceId() default ""; /** * The service id with optional protocol prefix. Synonym for {@link #value() value}. */ @AliasFor("value") String name() default ""; /** * Sets the <code>@Qualifier</code> value for the feign client. */ String qualifier() default ""; /** * An absolute URL or resolvable hostname (the protocol is optional). */ String url() default ""; /** * Whether 404s should be decoded instead of throwing FeignExceptions */ boolean decode404() default false; /** * A custom <code>@Configuration</code> for the feign client. Can contain override * <code>@Bean</code> definition for the pieces that make up the client, for instance * {@link feign.codec.Decoder}, {@link feign.codec.Encoder}, {@link feign.Contract}. * * @see FeignClientsConfiguration for the defaults */ Class<?>[] configuration() default {}; /** * Fallback class for the specified Feign client interface. The fallback class must * implement the interface annotated by this annotation and be a valid spring bean. */ Class<?> fallback() default void.class; /** * Define a fallback factory for the specified Feign client interface. The fallback * factory must produce instances of fallback classes that implement the interface * annotated by {@link FeignClient}. The fallback factory must be a valid spring * bean. * * @see feign.hystrix.FallbackFactory for details. */ Class<?> fallbackFactory() default void.class; /** * Path prefix to be used by all method-level mappings. Can be used with or without * <code>@RibbonClient</code>. */ String path() default ""; /** * Whether to mark the feign proxy as a primary bean. Defaults to true. */ boolean primary() default true; }
怕以后又忘记,总结下目前项目中实际用到的 @FeignClient 注解中的参数,如下:
@FeignClient(value = "annoroad-alpha", url = "${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
上述内容就是如何解析SpringCloud @FeignClient参数的用法,你们学到知识或技能了吗?如果还想学到更多技能或者丰富自己的知识储备,欢迎关注亿速云行业资讯频道。
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