Feign动态代理源码分析
整体流程
自动装配
FeignClientsConfiguration
自动装载Feign.Builder、Decoder、Encoder、Contract等Bean至ApplicationContext。
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@Configuration(proxyBeanMethods = false)
public class FeignClientsConfiguration {
//默认解码器
@Bean
@ConditionalOnMissingBean
public Decoder feignDecoder() {
return new OptionalDecoder(
new ResponseEntityDecoder(new SpringDecoder(this.messageConverters)));
}
//默认编码器
@Bean
@ConditionalOnMissingBean
@ConditionalOnMissingClass("org.springframework.data.domain.Pageable")
public Encoder feignEncoder() {
return new SpringEncoder(this.messageConverters);
}
//默认协议规则
@Bean
@ConditionalOnMissingBean
public Contract feignContract(ConversionService feignConversionService) {
return new SpringMvcContract(this.parameterProcessors, feignConversionService);
}
//默认重试器
@Bean
@ConditionalOnMissingBean
public Retryer feignRetryer() {
return Retryer.NEVER_RETRY;
}
//默认日志工厂
@Bean
@ConditionalOnMissingBean(FeignLoggerFactory.class)
public FeignLoggerFactory feignLoggerFactory() {
return new DefaultFeignLoggerFactory(this.logger);
}
//默认构造器
@Bean
@Scope("prototype")
@ConditionalOnMissingBean
public Feign.Builder feignBuilder(Retryer retryer) {
return Feign.builder().retryer(retryer);
}
//默认Feign构造器
@Bean
@Scope("prototype")
@ConditionalOnMissingBean
public Feign.Builder feignBuilder(Retryer retryer) {
return Feign.builder().retryer(retryer);
}
//如果使用Hystrix，使用Hystrix的Feign构造器
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass({ HystrixCommand.class, HystrixFeign.class })
protected static class HystrixFeignConfiguration {
@Bean
@Scope("prototype")
@ConditionalOnMissingBean
@ConditionalOnProperty(name = "feign.hystrix.enabled")
public Feign.Builder feignHystrixBuilder() {
return HystrixFeign.builder();
}
}
}
FeignAutoConfiguration
FeignAutoConfiguration是Feign自动配置类，自动配置每个服务的Spring容器FeignContext，基于ApacheHttpClient或OkHttpClient自动配置Http客户端。
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@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(Feign.class)
@EnableConfigurationProperties({ FeignClientProperties.class,
FeignHttpClientProperties.class })
@Import(DefaultGzipDecoderConfiguration.class)
public class FeignAutoConfiguration {
//为每一个服务创建一个FeignContext
@Bean
public FeignContext feignContext() {
FeignContext context = new FeignContext();
context.setConfigurations(this.configurations);
return context;
}
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(ApacheHttpClient.class)
@ConditionalOnMissingClass("com.netflix.loadbalancer.ILoadBalancer")
@ConditionalOnMissingBean(CloseableHttpClient.class)
@ConditionalOnProperty(value = "feign.httpclient.enabled", matchIfMissing = true)
protected static class HttpClientFeignConfiguration {
//配置ApacheHttpClient客户端
@Bean
@ConditionalOnMissingBean(Client.class)
public Client feignClient(HttpClient httpClient) {
return new ApacheHttpClient(httpClient);
}
}
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(OkHttpClient.class)
@ConditionalOnMissingClass("com.netflix.loadbalancer.ILoadBalancer")
@ConditionalOnMissingBean(okhttp3.OkHttpClient.class)
@ConditionalOnProperty("feign.okhttp.enabled")
protected static class OkHttpFeignConfiguration {
//配置OkHttpClient客户端
@Bean
@ConditionalOnMissingBean(Client.class)
public Client feignClient(okhttp3.OkHttpClient client) {
return new OkHttpClient(client);
}
}
}
注册FeignClient Bean定义
EnableFeignClients
FeignClient入口，@EnableFeignClients注解标注在SpringBoot启动类上。
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@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(FeignClientsRegistrar.class)
public @interface EnableFeignClients {
//配置basePackages
String[] value() default {};
//配置basePackages
String[] basePackages() default {};
//
Class<?>[] basePackageClasses() default {};
//默认配置
Class<?>[] defaultConfiguration() default {};
//用@FeignClient注释的类列表。如果不为空，则禁用类路径扫描
Class<?>[] clients() default {};
}
FeignClientsRegistrar
负责扫描所有使用@FeignClient注解的接口，并创建BeanDefinition加载至ApplicationCongtext中。
FeignClientsRegistrar#registerBeanDefinitions
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class FeignClientsRegistrar implements ImportBeanDefinitionRegistrar, ResourceLoaderAware, EnvironmentAware {
@Override
public void registerBeanDefinitions(AnnotationMetadata metadata,BeanDefinitionRegistry registry) {
//如果包含默认配置则加载默认配置
registerDefaultConfiguration(metadata, registry);
//将所有符合要求的FeignClient的接口加载至注册表
registerFeignClients(metadata, registry);
}
}
FeignClientsRegistrar#registerFeignClients
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//扫描、解析、注册
public void registerFeignClients(AnnotationMetadata metadata,
BeanDefinitionRegistry registry) {
//扫描器
ClassPathScanningCandidateComponentProvider scanner = getScanner();
scanner.setResourceLoader(this.resourceLoader);
Set<String> basePackages;
Map<String, Object> attrs = metadata
.getAnnotationAttributes(EnableFeignClients.class.getName());
//类型过滤器，带有FeignClient注解的才符合条件
AnnotationTypeFilter annotationTypeFilter = new AnnotationTypeFilter(
FeignClient.class);
final Class<?>[] clients = attrs == null ? null
: (Class<?>[]) attrs.get("clients");
//获取基础扫描包路径
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)));
}
//循环扫描包路径下所有
for (String basePackage : basePackages) {
//根据annotationTypeFilter扫描符合条件的BeanDefinition
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"));
//注册
registerFeignClient(registry, annotationMetadata, attributes);
}
}
}
}
FeignClientsRegistrar#registerFeignClient
为每一个@FeignClient的接口创建一个FeignClientFactoryBean工厂实例并注册在Spring容器中。
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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 });
BeanDefinitionReaderUtils.registerBeanDefinition(holder, registry);
}
实例化FeignContext
FeignContext
每个服务对应一个Spring的ApplicationContext，关于这个服务的配置都从这个服务的FeignContext中获取。
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public class FeignContext extends NamedContextFactory<FeignClientSpecification> {
public FeignContext() {
super(FeignClientsConfiguration.class, "feign", "feign.client.name");
}
}
NamedContextFactory
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//用于管理所有服务关联的Spring容器
public abstract class NamedContextFactory<C extends NamedContextFactory.Specification>
implements DisposableBean, ApplicationContextAware {
//构造方法
public NamedContextFactory(Class<?> defaultConfigType, String propertySourceName,
String propertyName) {
this.defaultConfigType = defaultConfigType;
this.propertySourceName = propertySourceName;
this.propertyName = propertyName;
}
//从指定服务名称的Spring容器中获取指定类型的实例
public <T> T getInstance(String name, Class<T> type) {
AnnotationConfigApplicationContext context = getContext(name);
if (BeanFactoryUtils.beanNamesForTypeIncludingAncestors(context,
type).length > 0) {
return context.getBean(type);
}
return null;
}
//根据服务名称获取Spring容器，没有则创建一个此服务名的Spring容器
protected AnnotationConfigApplicationContext getContext(String name) {
if (!this.contexts.containsKey(name)) {
synchronized (this.contexts) {
if (!this.contexts.containsKey(name)) {
this.contexts.put(name, createContext(name));
}
}
}
return this.contexts.get(name);
}
}
创建Feign.Builder并生成负载均衡代理类
FeignClientFactoryBean
FeignClientFactoryBean主要负责设置Feign.Builder和生成FeignClient注解接口的代理类对象。
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class FeignClientFactoryBean implements FactoryBean<Object>, InitializingBean, ApplicationContextAware {
//设置Feign.Builder
protected Feign.Builder feign(FeignContext context) {
FeignLoggerFactory loggerFactory = get(context, FeignLoggerFactory.class);
Logger logger = loggerFactory.create(this.type);
// @formatter:off
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
//设置Feign配置，优先级从低到高分别是FeignClientsConfiguration配置->yml中default配置->yml中单个服务的配置
configureFeign(context, builder);
return builder;
}
//为builder设置配置
protected void configureFeign(FeignContext context, Feign.Builder builder) {
FeignClientProperties properties = this.applicationContext
.getBean(FeignClientProperties.class);
if (properties != null) {
if (properties.isDefaultToProperties()) {
//FeignClientsConfiguration配置
configureUsingConfiguration(context, builder);
//yml中default配置
configureUsingProperties(properties.getConfig().get(properties.getDefaultConfig()),builder);
//yml中单个服务的配置
configureUsingProperties(properties.getConfig().get(this.contextId),builder);
}else {
configureUsingProperties(properties.getConfig().get(properties.getDefaultConfig()),builder);
configureUsingProperties(properties.getConfig().get(this.contextId),builder);
configureUsingConfiguration(context, builder);
}
}
else {
configureUsingConfiguration(context, builder);
}
}
//返回代理对象
@Override
public Object getObject() throws Exception {
return getTarget();
}
//生成代理对象
<T> T getTarget() {
FeignContext context = this.applicationContext.getBean(FeignContext.class);
Feign.Builder builder = feign(context);
//如果不为空，硬编码默认生成代理类
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);
if (client != null) {
if (client instanceof LoadBalancerFeignClient) {
// not load balancing because we have a url,
// but ribbon is on the classpath, so unwrap
client = ((LoadBalancerFeignClient) client).getDelegate();
}
if (client instanceof FeignBlockingLoadBalancerClient) {
// not load balancing because we have a url,
// but Spring Cloud LoadBalancer is on the classpath, so unwrap
client = ((FeignBlockingLoadBalancerClient) client).getDelegate();
}
builder.client(client);
}
//使用HystrixTargeter或DefaultTargeter
Targeter targeter = get(context, Targeter.class);
return (T) targeter.target(this, builder, context,
new HardCodedTarget<>(this.type, this.name, url));
}
}
FeignRibbonClientAutoConfiguration
Feign整合RibbonClient自动配置类，返回与ApacheHttpClient、OkHttpClient或默认Client整合的LoadBalancerFeignClient。
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@ConditionalOnClass({ ILoadBalancer.class, Feign.class })
@ConditionalOnProperty(value = "spring.cloud.loadbalancer.ribbon.enabled",
matchIfMissing = true)
@Configuration(proxyBeanMethods = false)
@AutoConfigureBefore(FeignAutoConfiguration.class)
@EnableConfigurationProperties({ FeignHttpClientProperties.class })
@Import({ HttpClientFeignLoadBalancedConfiguration.class,
OkHttpFeignLoadBalancedConfiguration.class,
DefaultFeignLoadBalancedConfiguration.class })
public class FeignRibbonClientAutoConfiguration {}
DefaultTargeter
如果没有整合Hystrix,使用的是默认的DefaultTargeter。
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class DefaultTargeter implements Targeter {
@Override
public <T> T target(FeignClientFactoryBean factory, Feign.Builder feign,
FeignContext context, Target.HardCodedTarget<T> target) {
return feign.target(target);
}
}
HystrixTargeter
Hystrix对builder设置一些Hystrix相关操作比如说fallback。
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class HystrixTargeter implements Targeter {
@Override
public <T> T target(FeignClientFactoryBean factory, Feign.Builder feign,
FeignContext context, Target.HardCodedTarget<T> target) {
if (!(feign instanceof feign.hystrix.HystrixFeign.Builder)) {
return feign.target(target);
}
feign.hystrix.HystrixFeign.Builder builder = (feign.hystrix.HystrixFeign.Builder) feign;
String name = StringUtils.isEmpty(factory.getContextId()) ? factory.getName()
: factory.getContextId();
SetterFactory setterFactory = getOptional(name, context, SetterFactory.class);
if (setterFactory != null) {
builder.setterFactory(setterFactory);
}
Class<?> fallback = factory.getFallback();
if (fallback != void.class) {
return targetWithFallback(name, context, target, builder, fallback);
}
Class<?> fallbackFactory = factory.getFallbackFactory();
if (fallbackFactory != void.class) {
return targetWithFallbackFactory(name, context, target, builder,
fallbackFactory);
}
return feign.target(target);
}
//设置包含降级的代理类
private <T> T targetWithFallback(String feignClientName, FeignContext context,
Target.HardCodedTarget<T> target, HystrixFeign.Builder builder,
Class<?> fallback) {
T fallbackInstance = getFromContext("fallback", feignClientName, context,
fallback, target.type());
return builder.target(target, fallbackInstance);
}
//调用父类
public <T> T target(Target<T> target, T fallback) {
return build(fallback != null ? new FallbackFactory.Default<T>(fallback) : null)
.newInstance(target);
}
}
ReflectiveFeign
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public class ReflectiveFeign extends Feign {
//生成代理对象
@Override
public <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>();
for (Method method : target.type().getMethods()) {
if (method.getDeclaringClass() == Object.class) {
continue;
} else if (Util.isDefault(method)) {
DefaultMethodHandler handler = new DefaultMethodHandler(method);
defaultMethodHandlers.add(handler);
methodToHandler.put(method, handler);
} else {
methodToHandler.put(method, nameToHandler.get(Feign.configKey(target.type(), method)));
}
}
InvocationHandler handler = factory.create(target, methodToHandler);
T proxy = (T) Proxy.newProxyInstance(target.type().getClassLoader(),
new Class<?>[] {target.type()}, handler);
for (DefaultMethodHandler defaultMethodHandler : defaultMethodHandlers) {
defaultMethodHandler.bindTo(proxy);
}
return proxy;
}
}
注入Spring容器
通过 spring refresh()方法，触发 FeignClientFactoryBean.getObject()方法获得了代理类，然后完成注入 spring容器。
