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上一节给大家分享了 Spring Cloud OpenFeign 的启动流程,接下来给大家分享一下调用流程。话不多说,咱们间接开始。
视频:https://www.bilibili.com/video/BV1A84y1C7XD/
调用流程
xxxFeignClient
→ feign.ReflectiveFeign.FeignInvocationHandler#invoke
→ feign.InvocationHandlerFactory.MethodHandler#invoke
→ feign.SynchronousMethodHandler#invoke
→ feign.SynchronousMethodHandler#executeAndDecode
→ org.springframework.cloud.openfeign.loadbalancer.FeignBlockingLoadBalancerClient#execute
→ feign.Client.Default#execute
→ feign.AsyncResponseHandler#handleResponse
动静代理
feign.ReflectiveFeign.FeignInvocationHandler#invoke
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {return dispatch.get(method).invoke(args);
}
这里说一下 dispatch
属性,它的类型是 Map<Method, MethodHandler>
意思是,能够通过办法找到对应的 Handler,这样就能够进入到 SynchronousMethodHandler#invoke。
feign.SynchronousMethodHandler#executeAndDecode
从这个办法的名称也能看进去,这个是执行申请,并且实现解码的性能,这是一个外围的办法。
负载平衡
org.springframework.cloud.openfeign.loadbalancer.FeignBlockingLoadBalancerClient#execute
这个是实现平衡,实现将 URL 中服务名转成 实在的 IP。
上面咱们看看它是如何被主动注入的。
首先在 spring.factories
文件中,做了配置
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.cloud.openfeign.loadbalancer.FeignLoadBalancerAutoConfiguration
FeignLoadBalancerAutoConfiguration 中引入 DefaultFeignLoadBalancerConfiguration
@ConditionalOnClass(Feign.class)
@ConditionalOnBean({LoadBalancerClient.class, LoadBalancerClientFactory.class})
@AutoConfigureBefore(FeignAutoConfiguration.class)
@AutoConfigureAfter({BlockingLoadBalancerClientAutoConfiguration.class, LoadBalancerAutoConfiguration.class})
@EnableConfigurationProperties(FeignHttpClientProperties.class)
@Configuration(proxyBeanMethods = false)
// Order is important here, last should be the default, first should be optional
// see
// https://github.com/spring-cloud/spring-cloud-netflix/issues/2086#issuecomment-316281653
@Import({ HttpClientFeignLoadBalancerConfiguration.class, OkHttpFeignLoadBalancerConfiguration.class,
HttpClient5FeignLoadBalancerConfiguration.class, DefaultFeignLoadBalancerConfiguration.class })
public class FeignLoadBalancerAutoConfiguration {}
new FeignBlockingLoadBalancerClient,并且注入到 Spring Bean 中
@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties(LoadBalancerClientsProperties.class)
class DefaultFeignLoadBalancerConfiguration {
@Bean
@ConditionalOnMissingBean
@Conditional(OnRetryNotEnabledCondition.class)
public Client feignClient(LoadBalancerClient loadBalancerClient,
LoadBalancerClientFactory loadBalancerClientFactory) {return new FeignBlockingLoadBalancerClient(new Client.Default(null, null), loadBalancerClient,
loadBalancerClientFactory);
}
}
Http 申请
上面咱们看看 feign 是如何实现 Http 申请的。
feign.Client.Default#execute
@Override
public Response execute(Request request, Options options) throws IOException {HttpURLConnection connection = convertAndSend(request, options);
return convertResponse(connection, request);
}
次要就是在这个办法中,默认应用 jdk 实现 http 申请。
convertAndSend,这个办法做了两件事,一是,关上 Http 连贯,获取到 HttpURLConnection
,并设置相干属性;二是,如果有参数,就通过输入流(OutputStream
)写入参数。
convertResponse,这个办法返回的是 feign.Response
,咱们它有哪些属性:
public final class Response implements Closeable {
private final int status;
private final String reason;
private final Map<String, Collection<String>> headers;
private final Body body;
private final Request request;
private final ProtocolVersion protocolVersion;
}
首先,这里实现 Closeable 接口,所以必然有 close 办法,咱们看一下:
@Override
public void close() {Util.ensureClosed(body);
}
好了,明确了,body 实际上是写入流(InputStream
)。
总结一下:这里实现了 Http 申请,上传了参数,或取得了输出流。
Http 响应解决
看完了申请,咱们再回到 feign.SynchronousMethodHandler#executeAndDecode,看上面的代码
CompletableFuture<Object> resultFuture = new CompletableFuture<>();
asyncResponseHandler.handleResponse(resultFuture, metadata.configKey(), response,
metadata.returnType(),
elapsedTime);
try {if (!resultFuture.isDone())
throw new IllegalStateException("Response handling not done");
return resultFuture.join();} catch (CompletionException e) {Throwable cause = e.getCause();
if (cause != null)
throw cause;
throw e;
}
这里是通过 CompletableFuture,来拆卸响应后果。
feign.AsyncResponseHandler#handleResponse,这个办法就也就是解决 Http 响应后果的入口。
比方要判断状态码,获取后果,敞开输出流等。
响应后果解码
解码流程如下:
feign.AsyncResponseHandler#decode
→ org.springframework.cloud.openfeign.support.ResponseEntityDecoder#decode
→ org.springframework.cloud.openfeign.support.SpringDecoder#decode
→ org.springframework.cloud.openfeign.support.SpringDecoder.FeignResponseAdapter#FeignResponseAdapter
→ org.springframework.web.client.HttpMessageConverterExtractor#extractData
→ org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter#read
为什么须要解码呢?
http 响应的后果类型是 String,而咱们须要的是一个对象,比方:
@FeignClient(
value = "openfeign-goods-service",
path = "/goods"
)
public interface IGoodsFeignClient {@GetMapping("/list")
ResultTemplate<ListTemplate<GoodsModel>> list();}
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