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

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。