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

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									@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

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									@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。

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									/**

									 * 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：

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									@FeignClient(value = "annoroad-alpha",  url = "${annoroad.ms.annoroad-alpha.url}")

									public interface UserFacade {

									    @PostMapping(value = "/user/detail")

									    UserDto detail(@RequestParam("id") long id);

									}