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這篇文章主要介紹“Dubbo Consumer引用服務的方法是什么”的相關知識，小編通過實際案例向大家展示操作過程，操作方法簡單快捷，實用性強，希望這篇“Dubbo Consumer引用服務的方法是什么”文章能幫助大家解決問題。
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:dubbo="http://dubbo.apache.org/schema/dubbo"
xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://dubbo.apache.org/schema/dubbo http://dubbo.apache.org/schema/dubbo/dubbo.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
<context:property-placeholder/>
<dubbo:application name="serialization-java-consumer">
<dubbo:parameter key="qos.enable" value="true" />
<dubbo:parameter key="qos.accept.foreign.ip" value="false" />
<dubbo:parameter key="qos.port" value="33333" />
</dubbo:application>
<dubbo:registry address="zookeeper://${zookeeper.address:127.0.0.1}:2181"/>
<dubbo:reference id="demoService" check="true" interface="org.apache.dubbo.samples.serialization.api.DemoService"/>
</beans>在之前的章節中已經知道，Dubbo基于Spring自定義標簽規范實現了自定義標簽，通過自定義標簽完成了bean的加載，并且通過實現監聽Spring容器刷新完畢事件啟動dubbo客戶端。啟動客戶端伴隨著服務發布和服務的訂閱。
public class DubboConsumer {
public static void main(String[] args) {
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("spring/dubbo-demo-consumer.xml");
context.start();
DemoService demoService = context.getBean("demoService", DemoService.class);
String hello = demoService.sayHello("world");
System.out.println(hello);
}
}dubbo通過<dubbo:reference標簽引用服務，之后在程序中通過Spring的Context依賴查找(getBean)的方式獲取引用的服務的代理實例。<dubbo:reference加載的Bean是ReferenceBean，它實現了FactoryBean接口，getBean時會調用ReferenceBean的getObject()方法，這是獲取引用的入口。getBean方法會判斷Reference對象是否是空的，如果是空的，調用init方法。代碼如下：
@Override
public Object getObject() {
return get();
}ReferenceBean繼承了ReferenceConfig，當調用ReferenceBean的getObject()方法會調用ReferenceBean的get()方法。
public synchronized T get() {
if (destroyed) {
throw new IllegalStateException("The invoker of ReferenceConfig(" + url + ") has already destroyed!");
}
// 代理引用如果是空的，調用init
if (ref == null) {
init();
}
return ref;
}
public synchronized void init() {
if (initialized) {
return;
}
if (bootstrap == null) {
bootstrap = DubboBootstrap.getInstance();
bootstrap.init();
}
// 1. 檢查配置ConsumerConfig，有的話檢查配置，沒有就新建一個ConsumerConfig
// 2. 反射創建調用的API
// 3. 初始化ServiceMetadata
// 4. 注冊Consumer
// 5. 檢查ReferenceConfig，RegistryConfig，ConsumerConfig
checkAndUpdateSubConfigs();
checkStubAndLocal(interfaceClass);
// 檢查引用的接口是否mock
ConfigValidationUtils.checkMock(interfaceClass, this);
// consumer的信息
Map<String, String> map = new HashMap<String, String>();
map.put(SIDE_KEY, CONSUMER_SIDE);
// 添加運行時參數到map，包括：dubbo，release，timestamp，pid
ReferenceConfigBase.appendRuntimeParameters(map);
// 是不是泛化，不是的話進入條件
if (!ProtocolUtils.isGeneric(generic)) {
String revision = Version.getVersion(interfaceClass, version);
if (revision != null && revision.length() > 0) {
map.put(REVISION_KEY, revision);
}
// 獲取方法，生成包裝類，使用javassist，將生成的類放到WRAPPER_MAP中，key是org.apache.dubbo.samples.serialization.api.DemoService類對象，value是包裝類的實例
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 {
// method放到map，這里method是sayHello
map.put(METHODS_KEY, StringUtils.join(new HashSet<String>(Arrays.asList(methods)), COMMA_SEPARATOR));
}
}
// interface org.apache.dubbo.samples.serialization.api.DemoService
map.put(INTERFACE_KEY, interfaceName);
// 追加其他參數到map中
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);
// 所有數據在存到serviceMetadata的attachments中
serviceMetadata.getAttachments().putAll(map);
// 創建Service代理
ref = createProxy(map);
// 設置ServiceMetadata的Service代理引用
serviceMetadata.setTarget(ref);
serviceMetadata.addAttribute(PROXY_CLASS_REF, ref);
ConsumerModel consumerModel = repository.lookupReferredService(serviceMetadata.getServiceKey());
consumerModel.setProxyObject(ref);
consumerModel.init(attributes);
// 標記初始化完畢
initialized = true;
// dispatch a ReferenceConfigInitializedEvent since 2.7.4
dispatch(new ReferenceConfigInitializedEvent(this, invoker));
} @SuppressWarnings({"unchecked", "rawtypes", "deprecation"})
private T createProxy(Map<String, String> map) {
// 是否是InJvm，協議是InJvm
if (shouldJvmRefer(map)) {
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();
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)) {
urls.add(url.addParameterAndEncoded(REFER_KEY, StringUtils.toQueryString(map)));
} else {
urls.add(ClusterUtils.mergeUrl(url, map));
}
}
}
} else { // assemble URL from register center's configuration
// 如果protocols不是injvm檢查注冊中心
if (!LOCAL_PROTOCOL.equalsIgnoreCase(getProtocol())) {
checkRegistry();
// url列表，將zookeeper://改成registry://
List<URL> us = ConfigValidationUtils.loadRegistries(this, false);
if (CollectionUtils.isNotEmpty(us)) {
for (URL u : us) {
// 監控URL
URL monitorUrl = ConfigValidationUtils.loadMonitor(this, u);
// 如果有監控配置放到map中
if (monitorUrl != null) {
map.put(MONITOR_KEY, URL.encode(monitorUrl.toFullString()));
}
// 根據map中的信息生成url，這里生成的結果是
/*
registry://127.0.0.1:2181/org.apache.dubbo.registry.RegistryService?application=serialization-java-consumer&dubbo=2.0.2&pid=66793&qos.accept.foreign.ip=false&qos.enable=true&qos.port=33333&refer=application%3Dserialization-java-consumer%26check%3Dtrue%26dubbo%3D2.0.2%26init%3Dfalse%26interface%3Dorg.apache.dubbo.samples.serialization.api.DemoService%26methods%3DsayHello%26pid%3D66793%26qos.accept.foreign.ip%3Dfalse%26qos.enable%3Dtrue%26qos.port%3D33333%26register.ip%3D192.168.58.45%26release%3D2.7.7%26side%3Dconsumer%26sticky%3Dfalse%26timestamp%3D1636532992568®istry=zookeeper&release=2.7.7×tamp=1636533091883
*/
urls.add(u.addParameterAndEncoded(REFER_KEY, StringUtils.toQueryString(map)));
}
}
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.");
}
}
}
// 如果引用的URL就1個直接通過refer引用服務，這里和export相似，通過調用鏈實現的
// - ProtocolListenerWrapper
// - - ProtocolFilterWrapper
// - - - RegistryProtocol
if (urls.size() == 1) {
// 通過RegistryProtocol#refer引用服務
invoker = REF_PROTOCOL.refer(interfaceClass, urls.get(0));
} else {
// 如果是引用的服務多個，循環處理
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
// 集群處理
URL u = registryURL.addParameterIfAbsent(CLUSTER_KEY, ZoneAwareCluster.NAME);
// The invoker wrap relation would be like: ZoneAwareClusterInvoker(StaticDirectory) -> FailoverClusterInvoker(RegistryDirectory, routing happens here) -> Invoker
// 加入到集群中，這里包含集中集群處理模式，分別是：
invoker = CLUSTER.join(new StaticDirectory(u, invokers));
} else { // not a registry url, must be direct invoke.
invoker = CLUSTER.join(new StaticDirectory(invokers));
}
}
}
// invoer不可用處理
if (shouldCheck() && !invoker.isAvailable()) {
invoker.destroy();
throw new IllegalStateException("Failed to check the status of the service "
+ interfaceName
+ ". No provider available for the service "
+ (group == null ? "" : group + "/")
+ interfaceName +
(version == null ? "" : ":" + version)
+ " from the url "
+ invoker.getUrl()
+ " to the consumer "
+ NetUtils.getLocalHost() + " use dubbo version " + Version.getVersion());
}
if (logger.isInfoEnabled()) {
logger.info("Refer dubbo service " + interfaceClass.getName() + " from url " + invoker.getUrl());
}
/**
* @since 2.7.0
* ServiceData存儲，SPI機制，支持內存和遠程兩種方式
*/
String metadata = map.get(METADATA_KEY);
WritableMetadataService metadataService = WritableMetadataService.getExtension(metadata == null ? DEFAULT_METADATA_STORAGE_TYPE : metadata);
if (metadataService != null) {
URL consumerURL = new URL(CONSUMER_PROTOCOL, map.remove(REGISTER_IP_KEY), 0, map.get(INTERFACE_KEY), map);
metadataService.publishServiceDefinition(consumerURL);
}
// create service proxy
return (T) PROXY_FACTORY.getProxy(invoker, ProtocolUtils.isGeneric(generic));
}創建代理服務會創建Invoker，在引用服務過程中，會判斷協議是否為injvm，會根據協議做不同的處理，不是injvm協議會根據構造的配置信息（map）生成url并將url協議有zookeeper://改成registry://，然后通過Protocol接口refer方法引用服務，與發布服務相似，引用服務的過程也會包裝方法的調用鏈，如下：
- ProtocolListenerWrapper
- - ProtocolFilterWrapper
- - - RegistryProtocol
在refer的過程中會對一個服務端的引用和一個服務多個服務端的服務進行區分處理，對于有多個服務端的服務會進行集群處理（cluster），會講invoker列表加入到集群中，在調用過程中會根據集群策略來選擇不同的策略進行調用，集群策略實現也實現了SPI機制，
@Override
@SuppressWarnings("unchecked")
public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
// 注冊中心url 將 registry:// 轉成 zookeeper://
url = getRegistryUrl(url);
// 獲取注冊中心
Registry registry = registryFactory.getRegistry(url);
if (RegistryService.class.equals(type)) {
return proxyFactory.getInvoker((T) registry, type, url);
}
// 從url中解析出引用服務信息
Map<String, String> qs = StringUtils.parseQueryString(url.getParameterAndDecoded(REFER_KEY));
// 獲取分組
String group = qs.get(GROUP_KEY);
// 如果設置分組了，那么使用MergeableCluster策略
if (group != null && group.length() > 0) {
if ((COMMA_SPLIT_PATTERN.split(group)).length > 1 || "*".equals(group)) {
return doRefer(getMergeableCluster(), registry, type, url);
}
}
return doRefer(cluster, registry, type, url);
} private <T> Invoker<T> doRefer(Cluster cluster, Registry registry, Class<T> type, URL url) {
// 獲取集群目錄Directory，代表Invoker的集合
RegistryDirectory<T> directory = new RegistryDirectory<T>(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 subscribeUrl = new URL(CONSUMER_PROTOCOL, parameters.remove(REGISTER_IP_KEY), 0, type.getName(), parameters);
if (directory.isShouldRegister()) {
directory.setRegisteredConsumerUrl(subscribeUrl);
// 注冊消費者url
registry.register(directory.getRegisteredConsumerUrl());
}
directory.buildRouterChain(subscribeUrl);
// 向ZK發起訂閱服務，并設置監聽，這里比較復雜，最終會在ZookeeperRegistry#doSubscribe做服務訂閱
directory.subscribe(toSubscribeUrl(subscribeUrl));
// 加入集群
Invoker<T> invoker = cluster.join(directory);
List<RegistryProtocolListener> listeners = findRegistryProtocolListeners(url);
if (CollectionUtils.isEmpty(listeners)) {
return invoker;
}
RegistryInvokerWrapper<T> registryInvokerWrapper = new RegistryInvokerWrapper<>(directory, cluster, invoker, subscribeUrl);
for (RegistryProtocolListener listener : listeners) {
listener.onRefer(this, registryInvokerWrapper);
}
return registryInvokerWrapper;
}RegistryProtocol#doRefer方法，directory.subscribe會按照下面的調用鏈進行處理，最后調用ZookeeperRegistry#doSubscribe方法向zk注冊數據訂閱接口，并設置監聽。
- RegistryDirectory
- - ListenerRegistryWrapper
- - - FailbackRegistry
- - - - ZookeeperRegistry
@Override
public void doSubscribe(final URL url, final NotifyListener listener) {
try {
if (ANY_VALUE.equals(url.getServiceInterface())) {
String root = toRootPath();
// 初始化監聽
ConcurrentMap<NotifyListener, ChildListener> listeners = zkListeners.computeIfAbsent(url, k -> new ConcurrentHashMap<>());
ChildListener zkListener = listeners.computeIfAbsent(listener, k -> (parentPath, currentChilds) -> {
for (String child : currentChilds) {
child = URL.decode(child);
if (!anyServices.contains(child)) {
anyServices.add(child);
subscribe(url.setPath(child).addParameters(INTERFACE_KEY, child,
Constants.CHECK_KEY, String.valueOf(false)), k);
}
}
});
// 創建zk節點
zkClient.create(root, false);
List<String> services = zkClient.addChildListener(root, zkListener);
if (CollectionUtils.isNotEmpty(services)) {
for (String service : services) {
service = URL.decode(service);
anyServices.add(service);
subscribe(url.setPath(service).addParameters(INTERFACE_KEY, service,
Constants.CHECK_KEY, String.valueOf(false)), listener);
}
}
} else {
List<URL> urls = new ArrayList<>();
for (String path : toCategoriesPath(url)) {
ConcurrentMap<NotifyListener, ChildListener> listeners = zkListeners.computeIfAbsent(url, k -> new ConcurrentHashMap<>());
ChildListener zkListener = listeners.computeIfAbsent(listener, k -> (parentPath, currentChilds) -> ZookeeperRegistry.this.notify(url, k, toUrlsWithEmpty(url, parentPath, currentChilds)));
zkClient.create(path, false);
List<String> children = zkClient.addChildListener(path, zkListener);
if (children != null) {
urls.addAll(toUrlsWithEmpty(url, path, children));
}
}
//
notify(url, listener, urls);
}
} catch (Throwable e) {
throw new RpcException("Failed to subscribe " + url + " to zookeeper " + getUrl() + ", cause: " + e.getMessage(), e);
}
}refer服務創建Invoker時會調用該方法，該方法會通過getClients創建網絡客戶端，創建客戶端是會判斷客戶端是否為共享鏈接，根據connections創建客戶端ExchangeClient，然后通過initClient初始化客戶端，初始化過程中會判斷是否為延遲的客戶端LazyConnectExchangeClient，不是延遲客戶端，就會通過connect連接服務提供者，與服務提供者連接，具體建立連接流程不在這里說明，會在網絡通信介紹。
@Override
public <T> Invoker<T> protocolBindingRefer(Class<T> serviceType, URL url) throws RpcException {
optimizeSerialization(url);
// 創建RPC Invoker，通過getClients(url)創建網絡客戶端
DubboInvoker<T> invoker = new DubboInvoker<T>(serviceType, url, getClients(url), invokers);
// 將invoker添加到invokers中
invokers.add(invoker);
return invoker;
}
// 創建客戶端數組
private ExchangeClient[] getClients(URL url) {
// whether to share connection
// 是否共享鏈接
boolean useShareConnect = false;
int connections = url.getParameter(CONNECTIONS_KEY, 0);
List<ReferenceCountExchangeClient> shareClients = null;
// if not configured, connection is shared, otherwise, one connection for one service
if (connections == 0) {
useShareConnect = true;
/*
* The xml configuration should have a higher priority than properties.
* xml配置優先級高于properties配置
*/
String shareConnectionsStr = url.getParameter(SHARE_CONNECTIONS_KEY, (String) null);
connections = Integer.parseInt(StringUtils.isBlank(shareConnectionsStr) ? ConfigUtils.getProperty(SHARE_CONNECTIONS_KEY,
DEFAULT_SHARE_CONNECTIONS) : shareConnectionsStr);
// 共享鏈接客戶端
shareClients = getSharedClient(url, connections);
}
// 創建ExchangeClient
ExchangeClient[] clients = new ExchangeClient[connections];
for (int i = 0; i < clients.length; i++) {
if (useShareConnect) {
// 從共享客戶端獲取
clients[i] = shareClients.get(i);
} else {
// 初始化客戶端
clients[i] = initClient(url);
}
}
return clients;
}
// 初始化客戶端
private ExchangeClient initClient(URL url) {
// client type setting.
String str = url.getParameter(CLIENT_KEY, url.getParameter(SERVER_KEY, DEFAULT_REMOTING_CLIENT));
url = url.addParameter(CODEC_KEY, DubboCodec.NAME);
// enable heartbeat by default
url = url.addParameterIfAbsent(HEARTBEAT_KEY, String.valueOf(DEFAULT_HEARTBEAT));
// BIO is not allowed since it has severe performance issue.
if (str != null && str.length() > 0 && !ExtensionLoader.getExtensionLoader(Transporter.class).hasExtension(str)) {
throw new RpcException("Unsupported client type: " + str + "," +
" supported client type is " + StringUtils.join(ExtensionLoader.getExtensionLoader(Transporter.class).getSupportedExtensions(), " "));
}
ExchangeClient client;
try {
// connection should be lazy
if (url.getParameter(LAZY_CONNECT_KEY, false)) {
// 延遲加載客戶端
client = new LazyConnectExchangeClient(url, requestHandler);
} else {
// 通過NettyTransporter connect創建客戶端 與provider建立連接
client = Exchangers.connect(url, requestHandler);
}
} catch (RemotingException e) {
throw new RpcException("Fail to create remoting client for service(" + url + "): " + e.getMessage(), e);
}
return client;
}關于“Dubbo Consumer引用服務的方法是什么”的內容就介紹到這里了，感謝大家的閱讀。如果想了解更多行業相關的知識，可以關注億速云行業資訊頻道，小編每天都會為大家更新不同的知識點。
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