Open Feign 源码解析(二) --- 如何发送http请求-编程知识

Open Feign 源码解析二如何发送http请求？

如何组件化？

定义接口

public interface Client {Response execute(Request request, Options options) throws IOException;
}

是否存在已有的方案？

1）rest template

http client
ok http 。。。

如何整合已有的方案？

在这里插入图片描述

/** http client的适配器 */
public final class ApacheHttpClient implements Client {private final HttpClient client;public ApacheHttpClient(HttpClient client) {this.client = client;}@Overridepublic Response execute(Request request, Request.Options options) throws IOException {HttpUriRequest httpUriRequest;try {httpUriRequest = toHttpUriRequest(request, options);} catch (URISyntaxException e) {throw new IOException("URL '" + request.url() + "' couldn't be parsed into a URI", e);}HttpResponse httpResponse = client.execute(httpUriRequest);return toFeignResponse(httpResponse, request);}
}/** ok http 的适配器 */
public final class OkHttpClient implements Client {private final okhttp3.OkHttpClient delegate;public OkHttpClient(okhttp3.OkHttpClient delegate) {this.delegate = delegate;}@Overridepublic feign.Response execute(feign.Request input, feign.Request.Options options)throws IOException {okhttp3.OkHttpClient requestScoped;if (delegate.connectTimeoutMillis() != options.connectTimeoutMillis()|| delegate.readTimeoutMillis() != options.readTimeoutMillis()) {requestScoped = delegate.newBuilder().connectTimeout(options.connectTimeoutMillis(), TimeUnit.MILLISECONDS).readTimeout(options.readTimeoutMillis(), TimeUnit.MILLISECONDS).followRedirects(options.isFollowRedirects()).build();} else {requestScoped = delegate;}Request request = toOkHttpRequest(input);Response response = requestScoped.newCall(request).execute();return toFeignResponse(response, input).toBuilder().request(input).build();}
}

适配器需要引入的包(Pom.xml)

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

如何动态选择实现方案？

插拔式：

提供几种思路：

1）JAVA SPI -> 无法提供依赖注入，无法动态地选择实现类

2）Dubbo SPI -> 额外添加dubbo依赖，Dubbo SPI 与其业务模型耦合

3）springboot的自动装配 -> open feign 作为spirngcloud组件之一直接依托于springboot

技巧：如何快速找到自动装配类？

1）Ctrl+G -> find Usages 功能寻找new Instance

2）通过名字去猜 autoconfiguration结尾，其中带有feign开头

3）直接通过 spring.factories 文件去搜索

spring-cloud-openfeign-core-2.2.1.RELEASE.jar -> META-INF/spring.factories

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.cloud.openfeign.ribbon.FeignRibbonClientAutoConfiguration,\
org.springframework.cloud.openfeign.hateoas.FeignHalAutoConfiguration,\
org.springframework.cloud.openfeign.FeignAutoConfiguration,\
org.springframework.cloud.openfeign.encoding.FeignAcceptGzipEncodingAutoConfiguration,\
org.springframework.cloud.openfeign.encoding.FeignContentGzipEncodingAutoConfiguration,\
org.springframework.cloud.openfeign.loadbalancer.FeignLoadBalancerAutoConfiguration

feign 的带负载均衡的自动配置类

@Import({ HttpClientFeignLoadBalancedConfiguration.class,OkHttpFeignLoadBalancedConfiguration.class,DefaultFeignLoadBalancedConfiguration.class })
public class FeignRibbonClientAutoConfiguration {// ...
}

HttpClient适配器的配置类

@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(ApacheHttpClient.class)
@ConditionalOnProperty(value = "feign.httpclient.enabled", matchIfMissing = true)
@Import(HttpClientFeignConfiguration.class)
class HttpClientFeignLoadBalancedConfiguration {@Bean@ConditionalOnMissingBean(Client.class)public Client feignClient(CachingSpringLoadBalancerFactory cachingFactory,SpringClientFactory clientFactory, HttpClient httpClient) {ApacheHttpClient delegate = new ApacheHttpClient(httpClient);return new LoadBalancerFeignClient(delegate, cachingFactory, clientFactory);}
}

HttpClient的配置类

@Configuration(proxyBeanMethods = false)
@ConditionalOnMissingBean(CloseableHttpClient.class)
public class HttpClientFeignConfiguration {private final Timer connectionManagerTimer = new Timer("FeignApacheHttpClientConfiguration.connectionManagerTimer", true);private CloseableHttpClient httpClient;@Autowired(required = false)private RegistryBuilder registryBuilder;@Bean@ConditionalOnMissingBean(HttpClientConnectionManager.class)public HttpClientConnectionManager connectionManager(ApacheHttpClientConnectionManagerFactory connectionManagerFactory,FeignHttpClientProperties httpClientProperties) {final HttpClientConnectionManager 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;}// ...@Bean@ConditionalOnProperty(value = "feign.compression.response.enabled",havingValue = "false", matchIfMissing = true)public CloseableHttpClient httpClient(ApacheHttpClientFactory httpClientFactory,HttpClientConnectionManager httpClientConnectionManager,FeignHttpClientProperties httpClientProperties) {this.httpClient = createClient(httpClientFactory.createBuilder(),httpClientConnectionManager, httpClientProperties);return this.httpClient;}private CloseableHttpClient createClient(HttpClientBuilder builder,HttpClientConnectionManager httpClientConnectionManager,FeignHttpClientProperties httpClientProperties) {RequestConfig defaultRequestConfig = RequestConfig.custom().setConnectTimeout(httpClientProperties.getConnectionTimeout()).setRedirectsEnabled(httpClientProperties.isFollowRedirects()).build();CloseableHttpClient httpClient = builder.setDefaultRequestConfig(defaultRequestConfig).setConnectionManager(httpClientConnectionManager).build();return httpClient;}
}

如果同时依赖了http client和ok http？

// 依照import的顺序 http client -> ok http -> jdk
@Import({ HttpClientFeignLoadBalancedConfiguration.class,OkHttpFeignLoadBalancedConfiguration.class,DefaultFeignLoadBalancedConfiguration.class })
public class FeignRibbonClientAutoConfiguration {// ...
}

如何修改配置参数？

方法一：通过配置文件修改FeignHttpClientProperties的参数（属性绑定）

@Configuration(proxyBeanMethods = false)
@ConditionalOnMissingBean(CloseableHttpClient.class)
public class HttpClientFeignConfiguration { // http client的配置类@Bean@ConditionalOnMissingBean(HttpClientConnectionManager.class)public HttpClientConnectionManager connectionManager(ApacheHttpClientConnectionManagerFactory connectionManagerFactory,FeignHttpClientProperties httpClientProperties) {final HttpClientConnectionManager 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;}
}

方法二：修改配置类(@Bean) 替换源码中的配置

@Configuration
public class DefaultConfiguration {@Beanpublic HttpClientBuilder apacheHttpClientBuilder() {// 修改builder参数return HttpClientBuilder.create().setMaxConnTotal(1000);}
}

如何装配组件？

组件装配到哪里？

答案： SynchronousMethodHandler

public class ReflectiveFeign extends Feign {// .../** 创建JDK动态代理对象 */@Overridepublic <T> T newInstance(Target<T> target) {Map<String, MethodHandler> nameToHandler = targetToHandlersByName.apply(target);Map<Method, MethodHandler> methodToHandler = new LinkedHashMap<Method, MethodHandler>();List<DefaultMethodHandler> defaultMethodHandlers = new LinkedList<DefaultMethodHandler>();// 拿到接口中的所有方法for (Method method : target.type().getMethods()) {if (method.getDeclaringClass() == Object.class) {continue;} else if (Util.isDefault(method)) {// DefaultMethodHandler DefaultMethodHandler handler = new DefaultMethodHandler(method);defaultMethodHandlers.add(handler);methodToHandler.put(method, handler);} else {// SynchronousMethodHandler (我们正常使用的情况下, 通常MethodHandler都是SynchronousMethodHandler)// SynchronousMethodHandler他里面有个属性client, 把组件(就是对应http请求的组件), 就放在了这个类的client属性里面methodToHandler.put(method, nameToHandler.get(Feign.configKey(target.type(), method)));}}// 通过工厂创建FeignInvocationHandler对象并把methodToHandler封装进去// target: 里面三个属性(type: 对应的feign接口class加载器, name:服务名称, url:http://服务名称)// methodToHandler: 对应的方法事件InvocationHandler handler = factory.create(target, methodToHandler);// JDK动态代理的APIT proxy = (T) Proxy.newProxyInstance(target.type().getClassLoader(),new Class<?>[] {target.type()}, handler);for (DefaultMethodHandler defaultMethodHandler : defaultMethodHandlers) {defaultMethodHandler.bindTo(proxy);}return proxy;}// jdk动态代理的第三个参数InvocationHandlerstatic class FeignInvocationHandler implements InvocationHandler {private final Target target;private final Map<Method, MethodHandler> dispatch; // 每个方法封装到MethodHandlerFeignInvocationHandler(Target target, Map<Method, MethodHandler> dispatch) {this.target = checkNotNull(target, "target");this.dispatch = checkNotNull(dispatch, "dispatch for %s", target);}@Overridepublic Object invoke(Object proxy, Method method, Object[] args) throws Throwable {if ("equals".equals(method.getName())) {try {Object otherHandler =args.length > 0 && args[0] != null ? Proxy.getInvocationHandler(args[0]) : null;return equals(otherHandler);} catch (IllegalArgumentException e) {return false;}} else if ("hashCode".equals(method.getName())) {return hashCode();} else if ("toString".equals(method.getName())) {return toString();}// 通过方法, 找到对应的MethodHandler去调用它的invoke方法把对应的参数传递进去return dispatch.get(method).invoke(args);}}
}

final class SynchronousMethodHandler implements MethodHandler {private final MethodMetadata metadata;private final Target<?> target;private final Client client; // http 请求客户端private final Retryer retryer;private final List<RequestInterceptor> requestInterceptors;private final Logger logger;private final Logger.Level logLevel;private final RequestTemplate.Factory buildTemplateFromArgs;private final Options options;// ...private SynchronousMethodHandler(Target<?> target, Client client, Retryer retryer,List<RequestInterceptor> requestInterceptors, Logger logger,Logger.Level logLevel, MethodMetadata metadata,RequestTemplate.Factory buildTemplateFromArgs, Options options,Decoder decoder, ErrorDecoder errorDecoder, boolean decode404,boolean closeAfterDecode, ExceptionPropagationPolicy propagationPolicy) {// ...this.client = checkNotNull(client, "client for %s", target);// ...}/** 真正地调用每个方法 */  @Overridepublic Object invoke(Object[] argv) throws Throwable {RequestTemplate template = buildTemplateFromArgs.create(argv);Options options = findOptions(argv);Retryer retryer = this.retryer.clone();while (true) {try {return executeAndDecode(template, options); // 调用client} catch (RetryableException e) {try {retryer.continueOrPropagate(e);} catch (RetryableException th) {Throwable cause = th.getCause();if (propagationPolicy == UNWRAP && cause != null) {throw cause;} else {throw th;}}if (logLevel != Logger.Level.NONE) {logger.logRetry(metadata.configKey(), logLevel);}continue;}}}Object executeAndDecode(RequestTemplate template, Options options) throws Throwable {Request request = targetRequest(template);if (logLevel != Logger.Level.NONE) {logger.logRequest(metadata.configKey(), logLevel, request);}Response response;long start = System.nanoTime();try {response = client.execute(request, options); // 调用client组件的execute方法} catch (IOException e) {if (logLevel != Logger.Level.NONE) {logger.logIOException(metadata.configKey(), logLevel, e, elapsedTime(start));}throw errorExecuting(request, e);}// ...}  
}