spring feign使用笔记-白红宇

spring feign使用笔记

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发布时间：2019-06-18

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开启日志支持

@Bean    public Logger.Level feignLoggerLevel() {        return Logger.Level.FULL;    }

源码:

package feign;...  public enum Level {    /**     * No logging.     */    NONE,    /**     * Log only the request method and URL and the response status code and execution time.     */    BASIC,    /**     * Log the basic information along with request and response headers.     */    HEADERS,    /**     * Log the headers, body, and metadata for both requests and responses.     */    FULL  }...

使用http client发起请求,替换原生的connection

加入dependency,自动注入使用httpclient


                    
     
      io.github.openfeign
                     
     
      feign-httpclient
                     
     
      9.5.0
                 
                
                    
     
      org.apache.httpcomponents
                     
     
      httpclient
                     
     
      4.5.3

查看源码 spring-cloud-netflix-core-1.3.1.RELEASE.jar,可以明显看到如下代码,当存在ApacheHttpClient.class...

org.springframework.cloud.netflix.feign.ribbon;,,,public class FeignRibbonClientAutoConfiguration{    ...	@Configuration	@ConditionalOnClass(ApacheHttpClient.class)	@ConditionalOnProperty(value = "feign.httpclient.enabled", matchIfMissing = true)	protected static class HttpClientFeignLoadBalancedConfiguration {		@Autowired(required = false)		private HttpClient httpClient;		@Bean		@ConditionalOnMissingBean(Client.class)		public Client feignClient(CachingSpringLoadBalancerFactory cachingFactory,				SpringClientFactory clientFactory) {			ApacheHttpClient delegate;			if (this.httpClient != null) {				delegate = new ApacheHttpClient(this.httpClient);			}			else {				delegate = new ApacheHttpClient();			}			return new LoadBalancerFeignClient(delegate, cachingFactory, clientFactory);		}	},,,

feign 执行逻辑

1 将FeignClient注解的interface 交由feign.ReflectiveFeign创建代理feign.ReflectiveFeign.FeignInvocationHandler.

2 method代理feign.InvocationHandlerFactory.MethodHandler.默认是SynchronousMethodHandler实现类,执行method时,调用executeAndDecode第一行,顺序调用拦截器.

...  Object executeAndDecode(RequestTemplate template) throws Throwable {    Request request = targetRequest(template);...  Request targetRequest(RequestTemplate template) {    for (RequestInterceptor interceptor : requestInterceptors) {      interceptor.apply(template);    }    return target.apply(new RequestTemplate(template));  }...

3 然后交由 client执行http请求,client有不同实现,具体可看上面FeignRibbonClientAutoConfiguration

FeignClient注解

value,name: 二选一,都是一个东西.可以注入

serviceId: 过期了.

url: 不用多说,可以注入(注:一个cloud集群可以不用url,会自动根据name去找集群中服务发起请求)

configuration: 只对当前fegin生效的配置,而不是全局配置.(注:该类不要被扫描注入了)

fallback: 失败回调

path: 该path会作为method上path的前缀

其他参数略

例:

@Slf4jpublic class UserFeignConfiguration {    @Value("${spring.application.name:}")    private String applicationName;    @Bean    public RequestInterceptor userInterceptor() {        log.info("--------定义RequestInterceptor");        RequestInterceptor requestInterceptor = new RequestInterceptor() {            @Override            public void apply(RequestTemplate template) {                template.header("sysCode", applicationName);            }        };        return requestInterceptor;    }}@FeignClient(value = "token", url = "${nirvana.user.url}/v2", configuration = UserFeignConfiguration.class,fallback = TokenRemoteService.TokenRemoteServiceFallback.class)public interface TokenRemoteService {    @PostMapping(value = "/queryToken")    Result
    
      queryToken(TokenBean tokenBean);    @Component    @Slf4j    class TokenRemoteServiceFallback implements TokenRemoteService{        @Override        public Result
     
       queryToken(TokenBean tokenBean) {            log.info("TokenRemoteServiceFallback");            return null;        }    }}