【知识库】--Dubbo ReferenceBean获取 -- 源码过程（254）

此段分析的由来：

     <dubbo:reference/> 自定义标签被spring加载时生成ReferenceBean，而ReferenceBean类的定义

public class ReferenceBean<T> extends ReferenceConfig<T> implements FactoryBean, ApplicationContextAware, InitializingBean, DisposableBean

看到实现了spring的FactoryBean 他有一个接口用来获取代理对象：getObject().其实对于dubbo来说就是生成对远程服务调用的代理。

public Object getObject() throws Exception {
return get();
}

继续调用

ReferenceConfig

public synchronized T get() {
if (destroyed) {
throw new IllegalStateException("Already destroyed!");
}
if (ref == null) {
init();
}
return ref;
}

继续调用：

private void init() {
if (initialized) {
return;
}
checkAndLoadConfig();
ref = createProxy();
initialized = true;
}

@SuppressWarnings({"unchecked", "rawtypes", "deprecation"})
private T createProxy() {
URL tmpUrl = new URL("temp", "localhost", 0, initedParameterMap);
if (isJvmRefer(tmpUrl)) {
URL url = new URL(Constants.LOCAL_PROTO
4000
COL, NetUtils.LOCALHOST, 0, interfaceClass.getName()).addParameters(initedParameterMap);
invoker = refprotocol.refer(interfaceClass, url);
if (logger.isInfoEnabled()) {
logger.info("Using injvm service " + interfaceClass.getName());
}
} else {
urls.addAll(getInvokerUrls());//获取registryUrls
invoker = getClusterInvoker(urls);//伪装策略
}
Boolean c = check;
if (c == null && consumer != null) {
c = consumer.isCheck();
}
if (c == null) {
c = true; // default true
}
if (c && !invoker.isAvailable()) {
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());
}
// 创建服务代理
return (T) proxyFactory.getProxy(invoker);
}

private List<URL> getInvokerUrls() {
List<URL> urlList = Lists.newArrayList();
if (url != null && url.length() > 0) { // 用户指定URL，指定的URL可能是对点对直连地址，也可能是注册中心URL
String[] us = Constants.SEMICOLON_SPLIT_PATTERN.split(url);
if (us != null && us.length > 0) {
for (String u : us) {
URL url = URL.valueOf(u);
if (url.getPath() == null || url.getPath().length() == 0) {
url = url.setPath(interfaceName);
}
if (Constants.REGISTRY_PROTOCOL.equals(url.getProtocol())) {
urlList.add(url.addParameterAndEncoded(Constants.REFER_KEY, StringUtils.toQueryString(initedParameterMap)));
} else {
urlList.add(ClusterUtils.mergeUrl(url, initedParameterMap));//此处应该是不是dubbo://127.0.0.1:20880...等待debug
}
}
}
} else { // 通过注册中心配置拼装URL
List<URL> us = loadRegistries(false);
if (us != null && us.size() > 0) {
for (URL u : us) {
URL monitorUrl = loadMonitor(u);
if (monitorUrl != null) {
initedParameterMap.put(Constants.MONITOR_KEY, URL.encode(monitorUrl.toFullString()));
}
Map<String, String> params = Maps.newHashMap(this.initedParameterMap);
String quota = u.getParameter(Constants.REGISTRY_WEIGHT_KEY);
if (!Strings.isNullOrEmpty(quota)) {
params.put(Constants.REGISTRY_WEIGHT_KEY, quota);
}
String unit = u.getParameter(Constants.QDUBBO_UNIT);
if (!Strings.isNullOrEmpty(unit)) {
params.put(Constants.QDUBBO_UNIT, unit);
}
urlList.add(u.removeParameter(Constants.REGISTRY_WEIGHT_KEY).addParameterAndEncoded(Constants.REFER_KEY,  StringUtils.toQueryString(params))); //增加REFER_KEY = "refer"; 结果例如registry://127.0.0.1:9098/com.alibaba.dubbo.registry.RegistryService?application=demo-consumer&dubbo=2.0.0&pid=2484&refer=application%3Ddemo-consumer ...
}
}
if (urlList.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.");
}
}
return urlList;
}

跟进 -- getClusterInvoker(urls);

@SuppressWarnings("unchecked")
private Invoker<?> getClusterInvoker(List<URL> urls) {
List<Invoker<?>> invokers = new ArrayList<Invoker<?>>();
URL registryURL = null;
for (URL url : urls) {
invokers.add(refprotocol.refer(interfaceClass, url));       //SPI扩展接口自适应获取invoker
if (Constants.REGISTRY_PROTOCOL.equals(url.getProtocol())) {// 注册中心协议  REGISTRY_PROTOCOL = "registry";

registryURL = url; // 用了最后一个registry url
}
}
if (registryURL != null) { // 有 注册中心协议的URL
if (useUnitCluster()) {
URL u = registryURL.addParameterIfAbsent(Constants.REGISTRY_KEY + "." + Constants.CLUSTER_KEY, FailfastCluster.NAME);
return registryCluster.join(new UnitDirectory(u, invokers));
} else {
URL u = registryURL.addParameterIfAbsent(Constants.REGISTRY_KEY + "." + Constants.CLUSTER_KEY, AvailableCluster.NAME);//默认是用available策略    伪装成一个invoker
return registryCluster.join(new StaticDirectory(u, invokers));
}
} else { // 不是 注册中心的URL
return cluster.join(new StaticDirectory(invokers));
}
}

最后使用代理工厂创建--代理T

// 创建服务代理
return (T) proxyFactory.getProxy(invoker);