dubbo源码3-registry

dubbo-registry包封装注册中心相关代码。

api层定义registry的基本接口，主要包括：

registryservice: 定义注册的基本操作，注册、取消注册、订阅、取消订阅

registryfactory：获取注册器工厂

abstractregistry: 缓存注册、订阅以及通知信息和执行通知触发

failbackregistry: 定义失败重试逻辑，是具体注册器的直接父类，该抽象类定义doRegister/doUnRegister/doSubscribe/doUnSubscribe方法由子类实现。

integration包中的RegistryProtocol组合底层Protocol，增加注册功能，在export服务时，会通过url里的protocol参数指定使用该类作为protocol的实现类，具体代码在Protocol自动生成的adapter中，生成的代码如下：

package org.apache.dubbo.rpc;
import org.apache.dubbo.common.extension.ExtensionLoader;
public class Protocol$Adaptive implements org.apache.dubbo.rpc.Protocol {
public void destroy()  {
throw new UnsupportedOperationException("The method public abstract void org.apache.dubbo.rpc.Protocol.destroy() of interface org.apache.dubbo.rpc.Protocol is not adaptive method!");
}
public int getDefaultPort()  {
throw new UnsupportedOperationException("The method public abstract int org.apache.dubbo.rpc.Protocol.getDefaultPort() of interface org.apache.dubbo.rpc.Protocol is not adaptive method!");
}
public org.apache.dubbo.rpc.Exporter export(org.apache.dubbo.rpc.Invoker arg0) throws org.apache.dubbo.rpc.RpcException {
if (arg0 == null) throw new IllegalArgumentException("org.apache.dubbo.rpc.Invoker argument == null");
if (arg0.getUrl() == null) throw new IllegalArgumentException("org.apache.dubbo.rpc.Invoker argument getUrl() == null");
org.apache.dubbo.common.URL url = arg0.getUrl();
String extName = ( url.getProtocol() == null ? "dubbo" : url.getProtocol() );
if(extName == null) throw new IllegalStateException("Failed to get extension (org.apache.dubbo.rpc.Protocol) name from url (" + url.toString() + ") use keys([protocol])");
org.apache.dubbo.rpc.Protocol extension = (org.apache.dubbo.rpc.Protocol)ExtensionLoader.getExtensionLoader(org.apache.dubbo.rpc.Protocol.class).getExtension(extName);
return extension.export(arg0);
}
public java.util.List getServers()  {
throw new UnsupportedOperationException("The method public default java.util.List org.apache.dubbo.rpc.Protocol.getServers() of interface org.apache.dubbo.rpc.Protocol is not adaptive method!");
}
public org.apache.dubbo.rpc.Invoker refer(java.lang.Class arg0, org.apache.dubbo.common.URL arg1) throws org.apache.dubbo.rpc.RpcException {
if (arg1 == null) throw new IllegalArgumentException("url == null");
org.apache.dubbo.common.URL url = arg1;
String extName = ( url.getProtocol() == null ? "dubbo" : url.getProtocol() );
if(extName == null) throw new IllegalStateException("Failed to get extension (org.apache.dubbo.rpc.Protocol) name from url (" + url.toString() + ") use keys([protocol])");
org.apache.dubbo.rpc.Protocol extension = (org.apache.dubbo.rpc.Protocol)ExtensionLoader.getExtensionLoader(org.apache.dubbo.rpc.Protocol.class).getExtension(extName);
return extension.refer(arg0, arg1);
}
}

 主要关注的是  String extName = ( url.getProtocol() == null ? "dubbo" : url.getProtocol() ); 这句代码，表示从url中取protocol来决定使用哪个protocol。

具体url设置是在ServiceConfig类的如下代码:

 这里的url协议是register，然后在dubbo-register包下的meta-inf的internal目录下org.apache.dubbo.rpc.Protocol里register对应的类是： InterfaceCompatibleRegistryProtocol。 该类就是RegistryProtocol的子类，所以间接实例化了RegistryProtocol。

其他包和类待补充，目前没有看到哪里有使用到。