服务引用
服务引用的流程可以概括为以下五点
- 两种模式（饿汉式/懒汉式）
- 组装URL并向注册中心注册
- 获取服务提供者信息并根据协议（默认Dubbo协议）开始Invoker的创建流程
- 通过Cluster包装Invoker（默认FailoverCluster）
- 返回代理类
饿汉式与懒汉式
Dubbo 服务引用的时机
- 饿汉式：饿汉式是通过实现 Spring 的
InitializingBean接口中的afterPropertiesSet方法，容器通过调用ReferenceBean的afterPropertiesSet方法时引入服务。 - 懒汉式：只有当这个服务被注入到其他类中时启动引入流程
注释：我们创建出来的远程调用的代理对象，实际上是ReferenceBean的一个成员变量（相当于我们在代理对象上套了个壳，把这个壳作为一个bean注册到spring容器中）
关于这点的解释。如果 <dubbo:reference> 的init属性开启（饿汉式），创建完ReferenceBean 的时候，在afterProperties方法里面调用对应的getObject方法，将对应的Invoker的Bean创建出来并注册到容器中。而懒汉式则是在其他的Bean去注入它的时候，才会去进行Invoker的创建流程
然后ContextRefreshedEvent事件那一步的处理会将我上面没有去实例化的那些Invoker也实例化一次（个人猜测是那些懒加载没有被其他Bean注入的Bean）
为什么要是用FactoryBean接口的方式去创建对应的Bean。因为FactoryBean本身的作用是为了能够进行复杂的Bean逻辑创建，而不通过Spring本身的三级缓存的方式创建Bean。而且此处的Invoker还涉及到动态代理之类的情况，FactoryBean就很适合这种创建Bean场景
同样的，例如SpringCloud的Feign之类的也是通过这样的方式注入Bean
关键类 ReferenceConfig
核心源码
触发的地方
public <T> T get(ReferenceConfigBase<T> referenceConfig) {
String key = generator.generateKey(referenceConfig);
Class<?> type = referenceConfig.getInterfaceClass();
proxies.computeIfAbsent(type, _t -> new ConcurrentHashMap<>());
ConcurrentMap<String, Object> proxiesOfType = proxies.get(type);
proxiesOfType.computeIfAbsent(key, _k -> {
// 触发的地方，最终调用到init
Object proxy = referenceConfig.get();
referredReferences.put(key, referenceConfig);
return proxy;
});
return (T) proxiesOfType.get(key);
}
public synchronized void init() {
if (initialized) {
return;
}
if (bootstrap == null) {
bootstrap = DubboBootstrap.getInstance();
bootstrap.initialize();
}
checkAndUpdateSubConfigs();
checkStubAndLocal(interfaceClass);
ConfigValidationUtils.checkMock(interfaceClass, this);
Map<String, String> map = new HashMap<String, String>();
map.put(SIDE_KEY, CONSUMER_SIDE);
ReferenceConfigBase.appendRuntimeParameters(map);
if (!ProtocolUtils.isGeneric(generic)) {
String revision = Version.getVersion(interfaceClass, version);
if (revision != null && revision.length() > 0) {
map.put(REVISION_KEY, revision);
}
String[] methods = Wrapper.getWrapper(interfaceClass).getMethodNames();
if (methods.length == 0) {
logger.warn("No method found in service interface " + interfaceClass.getName());
map.put(METHODS_KEY, ANY_VALUE);
} else {
map.put(METHODS_KEY, StringUtils.join(new HashSet<String>(Arrays.asList(methods)), COMMA_SEPARATOR));
}
}
map.put(INTERFACE_KEY, interfaceName);
AbstractConfig.appendParameters(map, getMetrics());
AbstractConfig.appendParameters(map, getApplication());
AbstractConfig.appendParameters(map, getModule());
// remove 'default.' prefix for configs from ConsumerConfig
// appendParameters(map, consumer, Constants.DEFAULT_KEY);
AbstractConfig.appendParameters(map, consumer);
AbstractConfig.appendParameters(map, this);
MetadataReportConfig metadataReportConfig = getMetadataReportConfig();
if (metadataReportConfig != null && metadataReportConfig.isValid()) {
map.putIfAbsent(METADATA_KEY, REMOTE_METADATA_STORAGE_TYPE);
}
Map<String, AsyncMethodInfo> attributes = null;
if (CollectionUtils.isNotEmpty(getMethods())) {
attributes = new HashMap<>();
for (MethodConfig methodConfig : getMethods()) {
AbstractConfig.appendParameters(map, methodConfig, methodConfig.getName());
String retryKey = methodConfig.getName() + ".retry";
if (map.containsKey(retryKey)) {
String retryValue = map.remove(retryKey);
if ("false".equals(retryValue)) {
map.put(methodConfig.getName() + ".retries", "0");
}
}
AsyncMethodInfo asyncMethodInfo = AbstractConfig.convertMethodConfig2AsyncInfo(methodConfig);
if (asyncMethodInfo != null) {
// consumerModel.getMethodModel(methodConfig.getName()).addAttribute(ASYNC_KEY, asyncMethodInfo);
attributes.put(methodConfig.getName(), asyncMethodInfo);
}
}
}
String hostToRegistry = ConfigUtils.getSystemProperty(DUBBO_IP_TO_REGISTRY);
if (StringUtils.isEmpty(hostToRegistry)) {
hostToRegistry = NetUtils.getLocalHost();
} else if (isInvalidLocalHost(hostToRegistry)) {
throw new IllegalArgumentException("Specified invalid registry ip from property:" + DUBBO_IP_TO_REGISTRY + ", value:" + hostToRegistry);
}
map.put(REGISTER_IP_KEY, hostToRegistry);
serviceMetadata.getAttachments().putAll(map);
// 创建代理 即生成invoker（代理中包括invoker）
ref = createProxy(map);
serviceMetadata.setTarget(ref);
serviceMetadata.addAttribute(PROXY_CLASS_REF, ref);
ConsumerModel consumerModel = repository.lookupReferredService(serviceMetadata.getServiceKey());
consumerModel.setProxyObject(ref);
consumerModel.init(attributes);
initialized = true;
checkInvokerAvailable();
// dispatch a ReferenceConfigInitializedEvent since 2.7.4
dispatch(new ReferenceConfigInitializedEvent(this, invoker));
}
创建代理
重点在这个创建代理的方法里面
主要分为以下几点
- injvm =》 走jvm内部调用（自己服务中的dubbo接口调用）
- 配置了URL =》 点对点
- 未配置URL，从注册中心获取服务提供者信息
private T createProxy(Map<String, String> map) {
if (shouldJvmRefer(map)) {
// 本地调用的情况
URL url = new URL(LOCAL_PROTOCOL, LOCALHOST_VALUE, 0, interfaceClass.getName()).addParameters(map);
invoker = REF_PROTOCOL.refer(interfaceClass, url);
if (logger.isInfoEnabled()) {
logger.info("Using injvm service " + interfaceClass.getName());
}
} else {
urls.clear();
// 配置的url的情况 点对点/注册中心地址
if (url != null && url.length() > 0) { // user specified URL, could be peer-to-peer address, or register center's address.
String[] us = SEMICOLON_SPLIT_PATTERN.split(url);
if (us != null && us.length > 0) {
for (String u : us) {
URL url = URL.valueOf(u);
if (StringUtils.isEmpty(url.getPath())) {
url = url.setPath(interfaceName);
}
if (UrlUtils.isRegistry(url)) {
// 如果是注册中心，将map转换为查询字符串，并作为refer参数的值添加到url中
urls.add(url.addParameterAndEncoded(REFER_KEY, StringUtils.toQueryString(map)));
} else {
// 点对点直连，合并url，移除一些服务提供者的配置
urls.add(ClusterUtils.mergeUrl(url, map));
}
}
}
} else { // assemble URL from register center's configuration
// 未配置url的情况
// if protocols not injvm checkRegistry
if (!LOCAL_PROTOCOL.equalsIgnoreCase(getProtocol())) {
checkRegistry();
// 获取注册中心地址
List<URL> us = ConfigValidationUtils.loadRegistries(this, false);
if (CollectionUtils.isNotEmpty(us)) {
for (URL u : us) {
URL monitorUrl = ConfigValidationUtils.loadMonitor(this, u);
if (monitorUrl != null) {
map.put(MONITOR_KEY, URL.encode(monitorUrl.toFullString()));
}
urls.add(u.addParameterAndEncoded(REFER_KEY, StringUtils.toQueryString(map))); // registry://127.0.0.1:2181/org.apache.dubbo.registry.RegistryService?application=dubbo-demo-api-consumer&dubbo=2.0.2&pid=52327&refer=application=dubbo-demo-api-consumer&dubbo=2.0.2&generic=true&interface=org.apache.dubbo.demo.DemoService&pid=52327®ister.ip=10.167.10.19&side=consumer&sticky=false×tamp=1631087606024®istry=zookeeper×tamp=1631087917015
}
}
if (urls.isEmpty()) {
throw new IllegalStateException("No such any registry to reference " + interfaceName + " on the consumer " + NetUtils.getLocalHost() + " use dubbo version " + Version.getVersion() + ", please config <dubbo:registry address=\"...\" /> to your spring config.");
}
}
}
//
if (urls.size() == 1) {
invoker = REF_PROTOCOL.refer(interfaceClass, urls.get(0));
} else {
List<Invoker<?>> invokers = new ArrayList<Invoker<?>>();
URL registryURL = null;
for (URL url : urls) {
invokers.add(REF_PROTOCOL.refer(interfaceClass, url));
if (UrlUtils.isRegistry(url)) {
registryURL = url; // use last registry url
}
}
if (registryURL != null) { // registry url is available
// for multi-subscription scenario, use 'zone-aware' policy by default
String cluster = registryURL.getParameter(CLUSTER_KEY, ZoneAwareCluster.NAME);
// The invoker wrap sequence would be: ZoneAwareClusterInvoker(StaticDirectory) -> FailoverClusterInvoker(RegistryDirectory, routing happens here) -> Invoker
invoker = Cluster.getCluster(cluster, false).join(new StaticDirectory(registryURL, invokers));
} else { // not a registry url, must be direct invoke.
String cluster = CollectionUtils.isNotEmpty(invokers)
? (invokers.get(0).getUrl() != null ? invokers.get(0).getUrl().getParameter(CLUSTER_KEY, ZoneAwareCluster.NAME) : Cluster.DEFAULT)
: Cluster.DEFAULT;
invoker = Cluster.getCluster(cluster).join(new StaticDirectory(invokers));
}
}
}
if (logger.isInfoEnabled()) {
logger.info("Refer dubbo service " + interfaceClass.getName() + " from url " + invoker.getUrl());
}
URL consumerURL = new URL(CONSUMER_PROTOCOL, map.remove(REGISTER_IP_KEY), 0, map.get(INTERFACE_KEY), map);
MetadataUtils.publishServiceDefinition(consumerURL);
// create service proxy 创建代理服务
return (T) PROXY_FACTORY.getProxy(invoker, ProtocolUtils.isGeneric(generic));
}
此处细讲一下通过注册中心创建Invoker的方式（多个服务提供者的情况）
遍历注册中心，将注册中心所有的服务提供者信息（DynamicDirectory）汇集起来，创建出一个ClusterInvoker，并将ClusterInvoker的代理对象T返回给调用点
List<Invoker<?>> invokers = new ArrayList<Invoker<?>>();
URL registryURL = null;
for (URL url : urls) {
// 引用服务
invokers.add(REF_PROTOCOL.refer(interfaceClass, url));
if (UrlUtils.isRegistry(url)) {
registryURL = url; // use last registry url
}
}
if (registryURL != null) { // registry url is available
// for multi-subscription scenario, use 'zone-aware' policy by default
String cluster = registryURL.getParameter(CLUSTER_KEY, ZoneAwareCluster.NAME);
// The invoker wrap sequence would be: ZoneAwareClusterInvoker(StaticDirectory) -> FailoverClusterInvoker(RegistryDirectory, routing happens here) -> Invoker
invoker = Cluster.getCluster(cluster, false).join(new StaticDirectory(registryURL, invokers));
} else { // not a registry url, must be direct invoke.
String cluster = CollectionUtils.isNotEmpty(invokers)
? (invokers.get(0).getUrl() != null ? invokers.get(0).getUrl().getParameter(CLUSTER_KEY, ZoneAwareCluster.NAME) : Cluster.DEFAULT)
: Cluster.DEFAULT;
invoker = Cluster.getCluster(cluster).join(new StaticDirectory(invokers));
}
RegistryProtocol#refer
@Override
@SuppressWarnings("unchecked")
public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
url = getRegistryUrl(url);
// 获取注册中心
Registry registry = registryFactory.getRegistry(url);
if (RegistryService.class.equals(type)) {
return proxyFactory.getInvoker((T) registry, type, url);
}
// group="a,b" or group="*"
Map<String, String> qs = StringUtils.parseQueryString(url.getParameterAndDecoded(REFER_KEY));
String group = qs.get(GROUP_KEY);
if (group != null && group.length() > 0) {
if ((COMMA_SPLIT_PATTERN.split(group)).length > 1 || "*".equals(group)) {
return doRefer(Cluster.getCluster(MergeableCluster.NAME), registry, type, url);
}
}
Cluster cluster = Cluster.getCluster(qs.get(CLUSTER_KEY));
// 引用具体的服务
return doRefer(cluster, registry, type, url);
}
protected <T> Invoker<T> doRefer(Cluster cluster, Registry registry, Class<T> type, URL url) {
return interceptInvoker(getInvoker(cluster, registry, type, url), url);
}
具体的某一个服务提供者对应的Invoker
protected <T> ClusterInvoker<T> getInvoker(Cluster cluster, Registry registry, Class<T> type, URL url) {
// 封装成一个directory （invoker的集合）
DynamicDirectory<T> directory = createDirectory(type, url);
directory.setRegistry(registry);
directory.setProtocol(protocol);
// all attributes of REFER_KEY
Map<String, String> parameters = new HashMap<String, String>(directory.getConsumerUrl().getParameters());
URL urlToRegistry = new URL(CONSUMER_PROTOCOL, parameters.remove(REGISTER_IP_KEY), 0, type.getName(), parameters);
if (directory.isShouldRegister()) {
directory.setRegisteredConsumerUrl(urlToRegistry);
registry.register(directory.getRegisteredConsumerUrl());
}
// 建立路由规则链
directory.buildRouterChain(urlToRegistry);
// 订阅provider
directory.subscribe(toSubscribeUrl(urlToRegistry));
// 包装集群容错策略到invoker
return (ClusterInvoker<T>) cluster.join(directory);
}
懒汉式，ReferenceBean
底层使用的Spring的FactoryBean的方式去创建一个Bean对象，然后在我们具体的去注入这个对象的的时候才去实例化对应的Invoker代理对象
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