SpringCloud-Feign原理研究1(掃描、反射、實例化)

SpringCloud-Feign原理研究1(掃描、反射、實例化)

總結：

1. 掃描路徑下所有class，獲取到有@FeignClient聲明註解的接口類；
2. 反射獲取：url、path、參數信息；
3. 通過FeignClientFactoryBean提供getObject() 實例化對象。

/*
 * Copyright 2013-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.cloud.netflix.feign;

import java.io.IOException;
import java.lang.annotation.Annotation;
import java.net.MalformedURLException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.springframework.beans.factory.BeanClassLoaderAware;
import org.springframework.beans.factory.annotation.AnnotatedBeanDefinition;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanDefinitionHolder;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.BeanDefinitionReaderUtils;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.EnvironmentAware;
import org.springframework.context.ResourceLoaderAware;
import org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.annotation.AnnotationAttributes;
import org.springframework.core.env.Environment;
import org.springframework.core.io.ResourceLoader;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.core.type.ClassMetadata;
import org.springframework.core.type.classreading.MetadataReader;
import org.springframework.core.type.classreading.MetadataReaderFactory;
import org.springframework.core.type.filter.AbstractClassTestingTypeFilter;
import org.springframework.core.type.filter.AnnotationTypeFilter;
import org.springframework.core.type.filter.TypeFilter;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.StringUtils;

/**
 * @author Spencer Gibb
 * @author Jakub Narloch
 * @author Venil Noronha
 */
class FeignClientsRegistrar implements ImportBeanDefinitionRegistrar,
		ResourceLoaderAware, BeanClassLoaderAware, EnvironmentAware {

	// patterned after Spring Integration IntegrationComponentScanRegistrar
	// and RibbonClientsConfigurationRegistgrar

	private ResourceLoader resourceLoader;

	private ClassLoader classLoader;

	private Environment environment;

	public FeignClientsRegistrar() {
	}

	@Override
	public void setResourceLoader(ResourceLoader resourceLoader) {
		this.resourceLoader = resourceLoader;
	}

	@Override
	public void setBeanClassLoader(ClassLoader classLoader) {
		this.classLoader = classLoader;
	}

	@Override
	public void registerBeanDefinitions(AnnotationMetadata metadata,
			BeanDefinitionRegistry registry) {
		registerDefaultConfiguration(metadata, registry);
		registerFeignClients(metadata, registry);
	}

	private void registerDefaultConfiguration(AnnotationMetadata metadata,
			BeanDefinitionRegistry registry) {
		Map<String, Object> defaultAttrs = metadata
				.getAnnotationAttributes(EnableFeignClients.class.getName(), true);

		if (defaultAttrs != null && defaultAttrs.containsKey("defaultConfiguration")) {
			String name;
			if (metadata.hasEnclosingClass()) {
				name = "default." + metadata.getEnclosingClassName();
			}
			else {
				name = "default." + metadata.getClassName();
			}
			registerClientConfiguration(registry, name,
					defaultAttrs.get("defaultConfiguration"));
		}
	}

	public void registerFeignClients(AnnotationMetadata metadata,
			BeanDefinitionRegistry registry) {
		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)));
		}

		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"));

					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);
		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 = name + "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);
	}

	private void validate(Map<String, Object> attributes) {
		AnnotationAttributes annotation = AnnotationAttributes.fromMap(attributes);
		// This blows up if an aliased property is overspecified
		annotation.getAliasedString("name", FeignClient.class, null);
	}

	/* for testing */ String getName(Map<String, Object> attributes) {
		String name = (String) attributes.get("serviceId");
		if (!StringUtils.hasText(name)) {
			name = (String) attributes.get("name");
		}
		if (!StringUtils.hasText(name)) {
			name = (String) attributes.get("value");
		}
		name = resolve(name);
		if (!StringUtils.hasText(name)) {
			return "";
		}

		String host = null;
		try {
			String url;
			if (!name.startsWith("http://") && !name.startsWith("https://")) {
				url = "http://" + name;
			} else {
				url = name;
			}
			host = new URI(url).getHost();

		}
		catch (URISyntaxException e) {
		}
		Assert.state(host != null, "Service id not legal hostname (" + name + ")");
		return name;
	}

	private String resolve(String value) {
		if (StringUtils.hasText(value)) {
			return this.environment.resolvePlaceholders(value);
		}
		return value;
	}

	private String getUrl(Map<String, Object> attributes) {
		String url = resolve((String) attributes.get("url"));
		if (StringUtils.hasText(url) && !(url.startsWith("#{") && url.contains("}"))) {
			if (!url.contains("://")) {
				url = "http://" + url;
			}
			try {
				new URL(url);
			}
			catch (MalformedURLException e) {
				throw new IllegalArgumentException(url + " is malformed", e);
			}
		}
		return url;
	}

	private String getPath(Map<String, Object> attributes) {
		String path = resolve((String) attributes.get("path"));
		if (StringUtils.hasText(path)) {
			path = path.trim();
			if (!path.startsWith("/")) {
				path = "/" + path;
			}
			if (path.endsWith("/")) {
				path = path.substring(0, path.length() - 1);
			}
		}
		return path;
	}

	protected ClassPathScanningCandidateComponentProvider getScanner() {
		return new ClassPathScanningCandidateComponentProvider(false, this.environment) {

			@Override
			protected boolean isCandidateComponent(
					AnnotatedBeanDefinition beanDefinition) {
				if (beanDefinition.getMetadata().isIndependent()) {
					// TODO until SPR-11711 will be resolved
					if (beanDefinition.getMetadata().isInterface()
							&& beanDefinition.getMetadata()
									.getInterfaceNames().length == 1
							&& Annotation.class.getName().equals(beanDefinition
									.getMetadata().getInterfaceNames()[0])) {
						try {
							Class<?> target = ClassUtils.forName(
									beanDefinition.getMetadata().getClassName(),
									FeignClientsRegistrar.this.classLoader);
							return !target.isAnnotation();
						}
						catch (Exception ex) {
							this.logger.error(
									"Could not load target class: "
											+ beanDefinition.getMetadata().getClassName(),
									ex);

						}
					}
					return true;
				}
				return false;

			}
		};
	}

	protected Set<String> getBasePackages(AnnotationMetadata importingClassMetadata) {
		Map<String, Object> attributes = importingClassMetadata
				.getAnnotationAttributes(EnableFeignClients.class.getCanonicalName());

		Set<String> basePackages = new HashSet<>();
		for (String pkg : (String[]) attributes.get("value")) {
			if (StringUtils.hasText(pkg)) {
				basePackages.add(pkg);
			}
		}
		for (String pkg : (String[]) attributes.get("basePackages")) {
			if (StringUtils.hasText(pkg)) {
				basePackages.add(pkg);
			}
		}
		for (Class<?> clazz : (Class[]) attributes.get("basePackageClasses")) {
			basePackages.add(ClassUtils.getPackageName(clazz));
		}

		if (basePackages.isEmpty()) {
			basePackages.add(
					ClassUtils.getPackageName(importingClassMetadata.getClassName()));
		}
		return basePackages;
	}
	
	private String getQualifier(Map<String, Object> client) {
		if (client == null) {
			return null;
		}
		String qualifier = (String) client.get("qualifier");
		if (StringUtils.hasText(qualifier)) {
			return qualifier;
		}
		return null;
	}

	private String getClientName(Map<String, Object> client) {
		if (client == null) {
			return null;
		}
		String value = (String) client.get("value");
		if (!StringUtils.hasText(value)) {
			value = (String) client.get("name");
		}
		if (!StringUtils.hasText(value)) {
			value = (String) client.get("serviceId");
		}
		if (StringUtils.hasText(value)) {
			return value;
		}

		throw new IllegalStateException("Either 'name' or 'value' must be provided in @"
				+ FeignClient.class.getSimpleName());
	}

	private void registerClientConfiguration(BeanDefinitionRegistry registry, Object name,
			Object configuration) {
		BeanDefinitionBuilder builder = BeanDefinitionBuilder
				.genericBeanDefinition(FeignClientSpecification.class);
		builder.addConstructorArgValue(name);
		builder.addConstructorArgValue(configuration);
		registry.registerBeanDefinition(
				name + "." + FeignClientSpecification.class.getSimpleName(),
				builder.getBeanDefinition());
	}

	@Override
	public void setEnvironment(Environment environment) {
		this.environment = environment;
	}

	/**
	 * Helper class to create a {@link TypeFilter} that matches if all the delegates
	 * match.
	 *
	 * @author Oliver Gierke
	 */
	private static class AllTypeFilter implements TypeFilter {

		private final List<TypeFilter> delegates;

		/**
		 * Creates a new {@link AllTypeFilter} to match if all the given delegates match.
		 *
		 * @param delegates must not be {@literal null}.
		 */
		public AllTypeFilter(List<TypeFilter> delegates) {

			Assert.notNull(delegates);
			this.delegates = delegates;
		}

		@Override
		public boolean match(MetadataReader metadataReader,
				MetadataReaderFactory metadataReaderFactory) throws IOException {

			for (TypeFilter filter : this.delegates) {
				if (!filter.match(metadataReader, metadataReaderFactory)) {
					return false;
				}
			}

			return true;
		}
	}
}

/*
 * Copyright 2013-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.cloud.netflix.feign;

import java.util.Map;
import java.util.Objects;

import org.springframework.beans.BeanUtils;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.cloud.netflix.feign.ribbon.LoadBalancerFeignClient;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

import feign.Client;
import feign.Contract;
import feign.Feign;
import feign.Logger;
import feign.Request;
import feign.RequestInterceptor;
import feign.Retryer;
import feign.Target.HardCodedTarget;
import feign.codec.Decoder;
import feign.codec.Encoder;
import feign.codec.ErrorDecoder;

/**
 * @author Spencer Gibb
 * @author Venil Noronha
 * @author Eko Kurniawan Khannedy
 * @author Gregor Zurowski
 */
class FeignClientFactoryBean implements FactoryBean<Object>, InitializingBean,
		ApplicationContextAware {
	/***********************************
	 * WARNING! Nothing in this class should be @Autowired. It causes NPEs because of some lifecycle race condition.
	 ***********************************/

	private Class<?> type;

	private String name;

	private String url;

	private String path;

	private boolean decode404;

	private ApplicationContext applicationContext;

	private Class<?> fallback = void.class;

	private Class<?> fallbackFactory = void.class;

	@Override
	public void afterPropertiesSet() throws Exception {
		Assert.hasText(this.name, "Name must be set");
	}

	@Override
	public void setApplicationContext(ApplicationContext context) throws BeansException {
		this.applicationContext = context;
	}

	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

		configureFeign(context, builder);

		return builder;
	}

	protected void configureFeign(FeignContext context, Feign.Builder builder) {
		FeignClientProperties properties = applicationContext.getBean(FeignClientProperties.class);
		if (properties != null) {
			if (properties.isDefaultToProperties()) {
				configureUsingConfiguration(context, builder);
				configureUsingProperties(properties.getConfig().get(properties.getDefaultConfig()), builder);
				configureUsingProperties(properties.getConfig().get(this.name), builder);
			} else {
				configureUsingProperties(properties.getConfig().get(properties.getDefaultConfig()), builder);
				configureUsingProperties(properties.getConfig().get(this.name), builder);
				configureUsingConfiguration(context, builder);
			}
		} else {
			configureUsingConfiguration(context, builder);
		}
	}

	protected void configureUsingConfiguration(FeignContext context, Feign.Builder builder) {
		Logger.Level level = getOptional(context, Logger.Level.class);
		if (level != null) {
			builder.logLevel(level);
		}
		Retryer retryer = getOptional(context, Retryer.class);
		if (retryer != null) {
			builder.retryer(retryer);
		}
		ErrorDecoder errorDecoder = getOptional(context, ErrorDecoder.class);
		if (errorDecoder != null) {
			builder.errorDecoder(errorDecoder);
		}
		Request.Options options = getOptional(context, Request.Options.class);
		if (options != null) {
			builder.options(options);
		}
		Map<String, RequestInterceptor> requestInterceptors = context.getInstances(
				this.name, RequestInterceptor.class);
		if (requestInterceptors != null) {
			builder.requestInterceptors(requestInterceptors.values());
		}

		if (decode404) {
			builder.decode404();
		}
	}

	protected void configureUsingProperties(FeignClientProperties.FeignClientConfiguration config, Feign.Builder builder) {
		if (config == null) {
			return;
		}

		if (config.getLoggerLevel() != null) {
			builder.logLevel(config.getLoggerLevel());
		}

		if (config.getConnectTimeout() != null && config.getReadTimeout() != null) {
			builder.options(new Request.Options(config.getConnectTimeout(), config.getReadTimeout()));
		}

		if (config.getRetryer() != null) {
			Retryer retryer = getOrInstantiate(config.getRetryer());
			builder.retryer(retryer);
		}

		if (config.getErrorDecoder() != null) {
			ErrorDecoder errorDecoder = getOrInstantiate(config.getErrorDecoder());
			builder.errorDecoder(errorDecoder);
		}

		if (config.getRequestInterceptors() != null && !config.getRequestInterceptors().isEmpty()) {
			// this will add request interceptor to builder, not replace existing
			for (Class<RequestInterceptor> bean : config.getRequestInterceptors()) {
				RequestInterceptor interceptor = getOrInstantiate(bean);
				builder.requestInterceptor(interceptor);
			}
		}

		if (config.getDecode404() != null) {
			if (config.getDecode404()) {
				builder.decode404();
			}
		}
	}

	private <T> T getOrInstantiate(Class<T> tClass) {
		try {
			return applicationContext.getBean(tClass);
		} catch (NoSuchBeanDefinitionException e) {
			return BeanUtils.instantiateClass(tClass);
		}
	}

	protected <T> T get(FeignContext context, Class<T> type) {
		T instance = context.getInstance(this.name, type);
		if (instance == null) {
			throw new IllegalStateException("No bean found of type " + type + " for "
					+ this.name);
		}
		return instance;
	}

	protected <T> T getOptional(FeignContext context, Class<T> type) {
		return context.getInstance(this.name, type);
	}

	protected <T> T loadBalance(Feign.Builder builder, FeignContext context,
			HardCodedTarget<T> target) {
		Client client = getOptional(context, Client.class);
		if (client != null) {
			builder.client(client);
			Targeter targeter = get(context, Targeter.class);
			return targeter.target(this, builder, context, target);
		}

		throw new IllegalStateException(
				"No Feign Client for loadBalancing defined. Did you forget to include spring-cloud-starter-netflix-ribbon?");
	}

	@Override
	public Object getObject() throws Exception {
		FeignContext context = applicationContext.getBean(FeignContext.class);
		Feign.Builder builder = feign(context);

		if (!StringUtils.hasText(this.url)) {
			String url;
			if (!this.name.startsWith("http")) {
				url = "http://" + this.name;
			}
			else {
				url = this.name;
			}
			url += cleanPath();
			return loadBalance(builder, context, new HardCodedTarget<>(this.type,
					this.name, 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 lod balancing because we have a url,
				// but ribbon is on the classpath, so unwrap
				client = ((LoadBalancerFeignClient)client).getDelegate();
			}
			builder.client(client);
		}
		Targeter targeter = get(context, Targeter.class);
		return targeter.target(this, builder, context, new HardCodedTarget<>(
				this.type, this.name, url));
	}

	private String cleanPath() {
		String path = this.path.trim();
		if (StringUtils.hasLength(path)) {
			if (!path.startsWith("/")) {
				path = "/" + path;
			}
			if (path.endsWith("/")) {
				path = path.substring(0, path.length() - 1);
			}
		}
		return path;
	}

	@Override
	public Class<?> getObjectType() {
		return this.type;
	}

	@Override
	public boolean isSingleton() {
		return true;
	}

	public Class<?> getType() {
		return type;
	}

	public void setType(Class<?> type) {
		this.type = type;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getUrl() {
		return url;
	}

	public void setUrl(String url) {
		this.url = url;
	}

	public String getPath() {
		return path;
	}

	public void setPath(String path) {
		this.path = path;
	}

	public boolean isDecode404() {
		return decode404;
	}

	public void setDecode404(boolean decode404) {
		this.decode404 = decode404;
	}

	public ApplicationContext getApplicationContext() {
		return applicationContext;
	}

	public Class<?> getFallback() {
		return fallback;
	}

	public void setFallback(Class<?> fallback) {
		this.fallback = fallback;
	}

	public Class<?> getFallbackFactory() {
		return fallbackFactory;
	}

	public void setFallbackFactory(Class<?> fallbackFactory) {
		this.fallbackFactory = fallbackFactory;
	}

	@Override
	public boolean equals(Object o) {
		if (this == o) return true;
		if (o == null || getClass() != o.getClass()) return false;
		FeignClientFactoryBean that = (FeignClientFactoryBean) o;
		return Objects.equals(applicationContext, that.applicationContext) &&
				decode404 == that.decode404 &&
				Objects.equals(fallback, that.fallback) &&
				Objects.equals(fallbackFactory, that.fallbackFactory) &&
				Objects.equals(name, that.name) &&
				Objects.equals(path, that.path) &&
				Objects.equals(type, that.type) &&
				Objects.equals(url, that.url);
	}

	@Override
	public int hashCode() {
		return Objects.hash(applicationContext, decode404, fallback, fallbackFactory,
				name, path, type, url);
	}

	@Override
	public String toString() {
		return new StringBuilder("FeignClientFactoryBean{")
				.append("type=").append(type).append(", ")
				.append("name='").append(name).append("', ")
				.append("url='").append(url).append("', ")
				.append("path='").append(path).append("', ")
				.append("decode404=").append(decode404).append(", ")
				.append("applicationContext=").append(applicationContext).append(", ")
				.append("fallback=").append(fallback).append(", ")
				.append("fallbackFactory=").append(fallbackFactory)
				.append("}").toString();
	}

}