openfeigin配置相关

http请求client配置

默认情况下使用使用的HttpURLConnection，这样可以使用Apache HttpClient和OkHttp。在FeignAutoConfiguration自动装配类中会进行条件装配。

	@Configuration(proxyBeanMethods = false)@ConditionalOnClass(ApacheHttpClient.class)@ConditionalOnMissingBean(CloseableHttpClient.class)@ConditionalOnProperty(value = "feign.httpclient.enabled", matchIfMissing = true)@Conditional(HttpClient5DisabledConditions.class)protected static class HttpClientFeignConfiguration {@Bean@ConditionalOnMissingBean(HttpClientConnectionManager.class)public HttpClientConnectionManager connectionManager(ApacheHttpClientConnectionManagerFactory connectionManagerFactory,FeignHttpClientProperties httpClientProperties) {//HttpClientConnection连接信息final HttpClientConnection连接信息Manager connectionManager = connectionManagerFactory.newConnectionManager(httpClientProperties.isDisableSslValidation(), httpClientProperties.getMaxConnections(),httpClientProperties.getMaxConnectionsPerRoute(), httpClientProperties.getTimeToLive(),httpClientProperties.getTimeToLiveUnit(), this.registryBuilder);this.connectionManagerTimer.schedule(new TimerTask() {@Overridepublic void run() {connectionManager.closeExpiredConnections();}}, 30000, httpClientProperties.getConnectionTimerRepeat());return connectionManager;}@Beanpublic CloseableHttpClient httpClient(ApacheHttpClientFactory httpClientFactory,HttpClientConnectionManager httpClientConnectionManager,FeignHttpClientProperties httpClientProperties) {RequestConfig defaultRequestConfig = RequestConfig.custom().setConnectTimeout(httpClientProperties.getConnectionTimeout()).setRedirectsEnabled(httpClientProperties.isFollowRedirects()).build();this.httpClient = httpClientFactory.createBuilder().setConnectionManager(httpClientConnectionManager).setDefaultRequestConfig(defaultRequestConfig).build();return this.httpClient;}@Bean@ConditionalOnMissingBean(Client.class)public Client feignClient(HttpClient httpClient) {return new ApacheHttpClient(httpClient);}}

开启httpclient要在配置文件中配置feign.httpclient.enabled: true，除此之外还要添加对应的jar包依赖

        <dependency><groupId>io.github.openfeign</groupId><artifactId>feign-httpclient</artifactId></dependency>

httpclient相关的配置都被封装在FeignHttpClientProperties类中。可以配置连接超时时间，连接池信息等。

OkHttpClient连接配置信息同理，也是在自动装配类里进行条件装配。feign.okhttp.enabled要配置成true，同时添加相关依赖

<dependency><groupId>io.github.openfeign</groupId><artifactId>feign-okhttp</artifactId>
</dependency>

@FeignClient注解配置

属性	说明	示例
name	指定 FeignClient 的名字（在 Ribbon/Eureka/Nacos 里作为服务名使用），也是 feign.client.config.<name> 的 key	@FeignClient(name = "userservice")
value	name 的别名（和 name 作用相同）	@FeignClient(value = "userservice")
url	直连模式时指定调用地址（不走服务发现）	@FeignClient(name = "user", url = "http://localhost:8080")
path	为所有方法统一加上路径前缀	@FeignClient(name = "user", path = "/api/v1")
fallback	熔断降级时指定的回退实现类（必须实现当前接口）	@FeignClient(name = "user", fallback = UserClientFallback.class)
fallbackFactory	降级工厂，可以根据异常类型返回不同的回退实现	@FeignClient(name = "user", fallbackFactory = UserClientFallbackFactory.class)
configuration	指定当前客户端的专属配置类（Bean 定义：日志级别、编码器、解码器、拦截器等）	@FeignClient(name = "user", configuration = UserFeignConfig.class)
primary	是否作为 @Primary Bean 注册到 Spring 容器，默认 true	@FeignClient(name = "user", primary = false)
contextId	用于区分同一个 name 下的多个 FeignClient Bean，防止冲突	@FeignClient(name = "user", contextId = "userApiV2")

configuration 如果不指定，默认会使用FeignClientsConfiguration中的配置。

FeignContext

Spring Boot 启动时会加载 FeignAutoConfiguration，其中定义了一个 FeignContext Bean。

会为每个 FeignClient 创建一个子容器,FeiginContext内部有一个Map<String, AnnotationConfigApplicationContext> contexts 来存储每个FeignClient的配置容器信息，其中key是FeignClient 的contextId或name。

在FeignClientFactoryBean中getTarget()方法创建FeignClient 代理实例时，会创建对应的context

FeiginContext.getInstance(contextId, type)方法会尝试从contexts map中获取对应的ApplicationContext，如果获取不到就证明当前FeignClient还未初始化，就会创建一个AnnotationConfigApplicationContext，放到contexts map里，然后会执行容context的初始化，Annotation类型的容器会执行注解扫描，可能会花费一定的时间，由于FeignClientFactoryBean创建的代理类时懒加载的，所以会造成当feigin接口第一次请求时会偏慢。但是当前切换到apache httpclient后这样，FeignClient接口就不会延迟加载，因为有外部依赖，@FeignClient Bean接口需要依赖ApacheHttpClient Bean，就会启动时候初始化。