SpringCloud.Honxton 版本 OpenFeign原理
-
- 前置說明
- 如何使用
- springcloud 和 openfeign 整合原理
- 總結
前置說明
上篇介紹了openfeign的使用和原理, 那麼這篇将介紹和springcloud 的整合部分. 有了上一篇的基礎, 那麼在分析原理的時候就簡單很多了, 更多的将關注于springcloud 的整合部分.
使用的依賴
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
如何使用
按照慣例還是先介紹如何使用feign
@FeignClient("client2") // service-id
public interface HelloOpenfeignSpringcloud {
@RequestMapping(name=" /feign",method = RequestMethod.GET, produces="application/x-www-form-urlencoded")
String feign(@RequestParam("feign") String feign);
@RequestMapping(name="/feignPost",method = RequestMethod.POST, produces="application/x-www-form-urlencoded")
String feignPost(@RequestParam("feign") String feign);
@RequestMapping(name = "/feignJson",method = RequestMethod.POST , produces="application/json")
String feignJson(@RequestBody String feign);
}
另外還需要加上
@EnableFeignClients
注解放到啟動類上
可以看到, 整合之後的用法的優點有以下幾點
- 不在需要手動調用代理的生成
- 可以使用我們熟悉的springmvc注解
-
結合注冊中心之後,不需要我們指定url, 且能支援負載均衡
…
處此之外, springcloud 提供了熔斷器和feign的整合, 用法也很簡單, 就是給接口增加個實作類,作為降級處理的邏輯.
當然缺點也有很多啦, 包括傳遞檔案時會有些問題, 然後傳遞對象必須要用@RequestBody, 但是也算是一個公認較好的用戶端遠端調用架構。
springcloud 和 openfeign 整合原理
了解完基本使用, 那麼就是揭開springcloud整合feign面紗的時候了
以下是所有的feign的自動配置類
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
其中最重要的就是
FeignAutoConfiguration
以及
FeignRibbonClientAutoConfiguration
或者
FeignLoadBalancerAutoConfiguration
那麼我們一個個分析
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(Feign.class) // 條件裝配
@EnableConfigurationProperties({ FeignClientProperties.class,
FeignHttpClientProperties.class })
@Import(DefaultGzipDecoderConfiguration.class)
public class FeignAutoConfiguration {
@Autowired(required = false) // 單獨的feignclient配置
private List<FeignClientSpecification> configurations = new ArrayList<>();
@Bean // feignclient的 spring命名工廠, 主要根據不同的serviceId建立不同的applicationContext 然後擷取專屬的配置, 很友善的和其他的client進行配置的隔離
public FeignContext feignContext() {
FeignContext context = new FeignContext();
context.setConfigurations(this.configurations);
return context;
}
// 是否開啟了 feign和hystrix的整合
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(name = "feign.hystrix.HystrixFeign")
protected static class HystrixFeignTargeterConfiguration {
// 這裡的Targeter接口是, springcloud 的一個抽象, 預設的實作是DefaultTargeter ,會委托Feign.Builder的target方法, 也就是我上篇講到的
@Bean
@ConditionalOnMissingBean
public Targeter feignTargeter() {
return new HystrixTargeter();
}
}
// 沒有開啟hystrix 的情況
@Configuration(proxyBeanMethods = false)
@ConditionalOnMissingClass("feign.hystrix.HystrixFeign")
protected static class DefaultFeignTargeterConfiguration {
@Bean
@ConditionalOnMissingBean
public Targeter feignTargeter() {
return new DefaultTargeter();
}
}
// feign 的底層調用實作 , 這裡隻粘貼了和httpclient相關的bean 定義
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(ApacheHttpClient.class) // 一般不引入這個是不會觸發這個配置類
@ConditionalOnMissingClass("com.netflix.loadbalancer.ILoadBalancer")
@ConditionalOnMissingBean(CloseableHttpClient.class)
@ConditionalOnProperty(value = "feign.httpclient.enabled", matchIfMissing = true)
protected static class HttpClientFeignConfiguration {
private final Timer connectionManagerTimer = new Timer(
"FeignApacheHttpClientConfiguration.connectionManagerTimer", true);
@Autowired(required = false)
private RegistryBuilder registryBuilder;
private CloseableHttpClient httpClient;
@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() {
@Override
public void run() {
connectionManager.closeExpiredConnections();
}
}, 30000, httpClientProperties.getConnectionTimerRepeat());
return connectionManager;
}
@Bean
public 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;
}
// 這個client接口就是上篇講到的用于替換底層實作的地方, 這裡用httpclient來實作了, 但是通常不是使用這裡的這個bean後面會有提到
@Bean
@ConditionalOnMissingBean(Client.class)
public Client feignClient(HttpClient httpClient) {
return new ApacheHttpClient(httpClient);
}
@PreDestroy
public void destroy() throws Exception {
this.connectionManagerTimer.cancel();
if (this.httpClient != null) {
this.httpClient.close();
}
}
}
...
}
下面來分别介紹一下feign底層負載均衡的實作, 這裡有2種, 一種是ribbon的底層整合,另一種是我之前的文章介紹過的spring自己研發的loadbalancer.
@ConditionalOnClass({ ILoadBalancer.class, Feign.class })
@ConditionalOnProperty(value = "spring.cloud.loadbalancer.ribbon.enabled",
matchIfMissing = true)
@Configuration(proxyBeanMethods = false)
@AutoConfigureBefore(FeignAutoConfiguration.class) //在上一個自動配置之前配置
@EnableConfigurationProperties({ FeignHttpClientProperties.class })
@Import({ HttpClientFeignLoadBalancedConfiguration.class,
OkHttpFeignLoadBalancedConfiguration.class,
DefaultFeignLoadBalancedConfiguration.class }) // 這裡導入 相關底層client的是實作的client的bean配置
public class FeignRibbonClientAutoConfiguration {
@Bean
@Primary
@ConditionalOnMissingBean
@ConditionalOnMissingClass("org.springframework.retry.support.RetryTemplate")
public CachingSpringLoadBalancerFactory cachingLBClientFactory(
SpringClientFactory factory) {
return new CachingSpringLoadBalancerFactory(factory);
}
// 用于建立 負載均衡器 給Client 進行execute的委派執行
@Bean
@Primary
@ConditionalOnMissingBean
@ConditionalOnClass(name = "org.springframework.retry.support.RetryTemplate")
public CachingSpringLoadBalancerFactory retryabeCachingLBClientFactory(
SpringClientFactory factory, LoadBalancedRetryFactory retryFactory) {
return new CachingSpringLoadBalancerFactory(factory, retryFactory);
}
@Bean
@ConditionalOnMissingBean
public Request.Options feignRequestOptions() {
return LoadBalancerFeignClient.DEFAULT_OPTIONS;
}
}
//這裡介紹一個導入的底層client實作, 預設其實還是使用feign原生的DefaultClient
@Configuration(proxyBeanMethods = false)
class DefaultFeignLoadBalancedConfiguration {
@Bean
@ConditionalOnMissingBean
public Client feignClient(CachingSpringLoadBalancerFactory cachingFactory,
SpringClientFactory clientFactory) {
return new LoadBalancerFeignClient(new Client.Default(null, null), cachingFactory,
clientFactory);
}
}
另外看下另一個負載均衡器和feign的整合
// 實作非常的簡單
@ConditionalOnClass(Feign.class)
@ConditionalOnBean(BlockingLoadBalancerClient.class)
@AutoConfigureBefore(FeignAutoConfiguration.class)
@AutoConfigureAfter(FeignRibbonClientAutoConfiguration.class)
@EnableConfigurationProperties(FeignHttpClientProperties.class)
@Configuration(proxyBeanMethods = false)
@Import({ HttpClientFeignLoadBalancerConfiguration.class,
OkHttpFeignLoadBalancerConfiguration.class,
DefaultFeignLoadBalancerConfiguration.class }) //僅僅是進行了配置導入, 和上面ribbon 一樣
class FeignLoadBalancerAutoConfiguration {
}
// 這個導入的配置類也是提供一個Client的實作
@Configuration(proxyBeanMethods = false)
class DefaultFeignLoadBalancedConfiguration {
@Bean
@ConditionalOnMissingBean
public Client feignClient(CachingSpringLoadBalancerFactory cachingFactory,
SpringClientFactory clientFactory) {
return new LoadBalancerFeignClient(new Client.Default(null, null), cachingFactory,
clientFactory);
}
}
看完上面的全部配置類,我相信可能大家都暈了, 其實不用擔心, 因為下面就會講FeignClient掃描建立FeignClientFactoryBean的時候, 到時候就會将上面配置bean都注入進來使用.
首先是
@EnableFeignClients
注解就是開啟掃描的功能
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(FeignClientsRegistrar.class) //導入掃描器
public @interface EnableFeignClients {
String[] value() default {};
String[] basePackages() default {};//配置掃描的包
...
}
//@FeignClient掃描器
class FeignClientsRegistrar
implements ImportBeanDefinitionRegistrar, ResourceLoaderAware, EnvironmentAware {
public void registerFeignClients(AnnotationMetadata metadata,
BeanDefinitionRegistry registry) {
// 掃描器
ClassPathScanningCandidateComponentProvider scanner = getScanner();
scanner.setResourceLoader(this.resourceLoader);
Set<String> basePackages;
Map<String, Object> attrs = metadata
.getAnnotationAttributes(EnableFeignClients.class.getName());
AnnotationTypeFilter annotationTypeFilter = new AnnotationTypeFilter(
FeignClient.class);
final Class<?>[] clients = attrs == null ? null
: (Class<?>[]) attrs.get("clients");
if (clients == null || clients.length == 0) {
scanner.addIncludeFilter(annotationTypeFilter);
basePackages = getBasePackages(metadata);
}
else {
final Set<String> clientClasses = new HashSet<>();
basePackages = new HashSet<>();
for (Class<?> clazz : clients) {
basePackages.add(ClassUtils.getPackageName(clazz));
clientClasses.add(clazz.getCanonicalName());
}
AbstractClassTestingTypeFilter filter = new AbstractClassTestingTypeFilter() {
@Override
protected boolean match(ClassMetadata metadata) {
String cleaned = metadata.getClassName().replaceAll("\\$", ".");
return clientClasses.contains(cleaned);
}
};
scanner.addIncludeFilter(
new AllTypeFilter(Arrays.asList(filter, annotationTypeFilter)));
}
// 循環掃描和注冊beandefinition
for (String basePackage : basePackages) {
Set<BeanDefinition> candidateComponents = scanner
.findCandidateComponents(basePackage);
for (BeanDefinition candidateComponent : candidateComponents) {
if (candidateComponent instanceof AnnotatedBeanDefinition) {
// verify annotated class is an interface
AnnotatedBeanDefinition beanDefinition = (AnnotatedBeanDefinition) candidateComponent;
AnnotationMetadata annotationMetadata = beanDefinition.getMetadata();
Assert.isTrue(annotationMetadata.isInterface(),
"@FeignClient can only be specified on an interface");
Map<String, Object> attributes = annotationMetadata
.getAnnotationAttributes(
FeignClient.class.getCanonicalName());
String name = getClientName(attributes);
registerClientConfiguration(registry, name,
attributes.get("configuration"));
//注冊方法
registerFeignClient(registry, annotationMetadata, attributes);
}
}
}
}
private void registerFeignClient(BeanDefinitionRegistry registry,
AnnotationMetadata annotationMetadata, Map<String, Object> attributes) {
String className = annotationMetadata.getClassName();
BeanDefinitionBuilder definition = BeanDefinitionBuilder
.genericBeanDefinition(FeignClientFactoryBean.class);
validate(attributes);
definition.addPropertyValue("url", getUrl(attributes));
definition.addPropertyValue("path", getPath(attributes));
String name = getName(attributes);
definition.addPropertyValue("name", name);
String contextId = getContextId(attributes);
definition.addPropertyValue("contextId", contextId);
definition.addPropertyValue("type", className);
definition.addPropertyValue("decode404", attributes.get("decode404"));
definition.addPropertyValue("fallback", attributes.get("fallback"));
definition.addPropertyValue("fallbackFactory", attributes.get("fallbackFactory"));
definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);
String alias = contextId + "FeignClient";
AbstractBeanDefinition beanDefinition = definition.getBeanDefinition();
boolean primary = (Boolean) attributes.get("primary"); // has a default, won't be
// null
beanDefinition.setPrimary(primary);
String qualifier = getQualifier(attributes);
if (StringUtils.hasText(qualifier)) {
alias = qualifier;
}
BeanDefinitionHolder holder = new BeanDefinitionHolder(beanDefinition, className,
new String[] { alias });
// 注冊到beanfactotry
BeanDefinitionReaderUtils.registerBeanDefinition(holder, registry);
}
}
以上是關于掃描相關的實作原理, 所有打着注解的都接口, 最後都變成了
FeignClientFactoryBean
形式注冊成bean了, 接下來就簡單了, 隻要我們盯着
FeignClientFactoryBean
的getObject方法就能揭曉最後的謎底了.
class FeignClientFactoryBean
implements FactoryBean<Object>, InitializingBean, ApplicationContextAware {
<T> T getTarget() {
FeignContext context = this.applicationContext.getBean(FeignContext.class);
// 擷取Builder, 之後就是和上篇講的源碼類似了
Feign.Builder builder = feign(context);
if (!StringUtils.hasText(this.url)) {
if (!this.name.startsWith("http")) {
this.url = "http://" + this.name;
}
else {
this.url = this.name;
}
this.url += cleanPath();
return (T) loadBalance(builder, context,
new HardCodedTarget<>(this.type, this.name, this.url));
}
if (StringUtils.hasText(this.url) && !this.url.startsWith("http")) {
this.url = "http://" + this.url;
}
String url = this.url + cleanPath();
Client client = getOptional(context, Client.class); // 擷取負載均衡用戶端
if (client != null) {
if (client instanceof LoadBalancerFeignClient) {
client = ((LoadBalancerFeignClient) client).getDelegate();
}
builder.client(client);
}
// 這裡的 Targeter前面也有介紹, 這裡預設是 DefaultTargeter
Targeter targeter = get(context, Targeter.class);
return (T) targeter.target(this, builder, context, //這裡進去就是就會驚奇的發現就是上一篇的 入口方法
new HardCodedTarget<>(this.type, this.name, url));
}
protected Feign.Builder feign(FeignContext context) {
FeignLoggerFactory loggerFactory = get(context, FeignLoggerFactory.class);
Logger logger = loggerFactory.create(this.type);
// @formatter:off 其實我看到這裡會有個疑問, 這個bean是怎麼從 對應的命名applicationContext擷取的, 那麼下面會給出答案
Feign.Builder builder = get(context, Feign.Builder.class)
// required values
.logger(logger)
.encoder(get(context, Encoder.class))
.decoder(get(context, Decoder.class))
.contract(get(context, Contract.class));
// @formatter:on
configureFeign(context, builder);
return builder;
}
}
之前遺漏的一個小細節, 關于 Feign.Builder.class 這個bean是如何擷取的
// 這個是最早介紹的被注冊成bean 的, 其實還包含了一個配置類 FeignClientsConfiguration
public class FeignContext extends NamedContextFactory<FeignClientSpecification> {
public FeignContext() {
super(FeignClientsConfiguration.class, "feign", "feign.client.name");
}
}
@Configuration(proxyBeanMethods = false)
public class FeignClientsConfiguration {
...
@Bean
@Scope("prototype")
@ConditionalOnMissingBean
public Feign.Builder feignBuilder(Retryer retryer) {
return Feign.builder().retryer(retryer);
}
...
}
總結
最後總結一下, springcloud為了整合feign做了很多的工作, 包括很多為了結合負載均衡器 以及 hystrix 做的很多擴充實作。 這也是導緻配置類急劇膨脹 ,讓我們看的眼花缭亂, 不知道看完這篇文章有沒有讓你撥開雲霧見青天的趕腳,但是我也是盡可能的去将我所了解的講出來了, 要是覺得我有講錯的可以在下方評論交流。