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 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

以上为个人经验,希望能给大家一个参考,也希望大家多多支持。

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