Dubbo-Dubbo SPI 机制实现 默认的Adaptive

Dubbo SPI 机制实现 默认的Adaptive

1、最好的学习就是直接下载源码跟踪了解实现的思路

想要从根了解源码的实现原理，最好的思路就是下载源码debug一下，了解其核心思路的实现原理；这个其实有个前提，不是来不来就开始debug 这样的效率特别的低，最好还是先看看官方的文档或者博客查看其实现的思路到底是什么?

2、根据官方的Test用例中，debug到了生成的默认的 XXXX$Adaptive的源码的信息

ProxyFactory$Adaptive

package org.apache.dubbo.rpc;
import org.apache.dubbo.common.extension.ExtensionLoader;
public class ProxyFactory$Adaptive implements org.apache.dubbo.rpc.ProxyFactory {
    public java.lang.Object getProxy(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.getParameter("proxy", "javassist");
        if(extName == null) throw new IllegalStateException("Fail to get extension(org.apache.dubbo.rpc.ProxyFactory) name from url(" + url.toString() + ") use keys([proxy])");
        org.apache.dubbo.rpc.ProxyFactory extension = (org.apache.dubbo.rpc.ProxyFactory)ExtensionLoader.getExtensionLoader(org.apache.dubbo.rpc.ProxyFactory.class).getExtension(extName);
        return extension.getProxy(arg0);
    }
    public java.lang.Object getProxy(org.apache.dubbo.rpc.Invoker arg0, boolean arg1) 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.getParameter("proxy", "javassist");
        if(extName == null) throw new IllegalStateException("Fail to get extension(org.apache.dubbo.rpc.ProxyFactory) name from url(" + url.toString() + ") use keys([proxy])");
        org.apache.dubbo.rpc.ProxyFactory extension = (org.apache.dubbo.rpc.ProxyFactory)ExtensionLoader.getExtensionLoader(org.apache.dubbo.rpc.ProxyFactory.class).getExtension(extName);
        return extension.getProxy(arg0, arg1);
    }
    public org.apache.dubbo.rpc.Invoker getInvoker(java.lang.Object arg0, java.lang.Class arg1, org.apache.dubbo.common.URL arg2) throws org.apache.dubbo.rpc.RpcException {
        if (arg2 == null) throw new IllegalArgumentException("url == null");
        org.apache.dubbo.common.URL url = arg2;
        String extName = url.getParameter("proxy", "javassist");
        if(extName == null) throw new IllegalStateException("Fail to get extension(org.apache.dubbo.rpc.ProxyFactory) name from url(" + url.toString() + ") use keys([proxy])");
        org.apache.dubbo.rpc.ProxyFactory extension = (org.apache.dubbo.rpc.ProxyFactory)ExtensionLoader.getExtensionLoader(org.apache.dubbo.rpc.ProxyFactory.class).getExtension(extName);
        return extension.getInvoker(arg0, arg1, arg2);
    }
}

Protocol$Adaptive

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("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("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.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("Fail 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);
    }
    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("Fail 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);
    }
}

3、如何测试呢GenericServiceTest#testGeneric

根据这个类，#getAdaptiveExtension 获取到扩展选择的类的信息，就是上面自动生成的自适应扩展的class的文件的实例，然后动态的根据URL中的MAP中的参数进行选择哦！然后在通过获取到的key，根据名称选择具体的扩展的实例；

 @Test
    public void testGeneric() {
        DemoService server = new DemoServiceImpl();
        ProxyFactory proxyFactory = ExtensionLoader.getExtensionLoader(ProxyFactory.class).getAdaptiveExtension();
        Protocol protocol = ExtensionLoader.getExtensionLoader(Protocol.class).getAdaptiveExtension();
        URL url = URL.valueOf("dubbo://127.0.0.1:5342/" + DemoService.class.getName() + "?version=1.0.0");
        Exporter<DemoService> exporter = protocol.export(proxyFactory.getInvoker(server, DemoService.class, url));
        Invoker<DemoService> invoker = protocol.refer(DemoService.class, url);

        GenericService client = (GenericService) proxyFactory.getProxy(invoker, true);
        Object result = client.$invoke("sayHello", new String[]{"java.lang.String"}, new Object[]{"haha"});
        Assertions.assertEquals("hello haha", result);

        org.apache.dubbo.rpc.service.GenericService newClient = (org.apache.dubbo.rpc.service.GenericService) proxyFactory.getProxy(invoker, true);
        Object res = newClient.$invoke("sayHello", new String[]{"java.lang.String"}, new Object[]{"hehe"});
        Assertions.assertEquals("hello hehe", res);
        invoker.destroy();
        exporter.unexport();
    }

4、看一下代理工厂的扩展接口

默认是javassist，然后根据dubbo：org.apache.dubbo.common.URL中的参数去动态的选择哦，真正调用的时候通过这个自适应的代理转发调用的逻辑，其实这个默认的自适应的实现就是从URL中获取固定的参数啦

/**
 * ProxyFactory. (API/SPI, Singleton, ThreadSafe)
 */
@SPI("javassist")
public interface ProxyFactory {

    /**
     * create proxy.
     *
     * @param invoker
     * @return proxy
     */
    @Adaptive({Constants.PROXY_KEY})
    <T> T getProxy(Invoker<T> invoker) throws RpcException;

    /**
     * create proxy.
     *
     * @param invoker
     * @return proxy
     */
    @Adaptive({Constants.PROXY_KEY})
    <T> T getProxy(Invoker<T> invoker, boolean generic) throws RpcException;

    /**
     * create invoker.
     *
     * @param 
     * @param proxy
     * @param type
     * @param url
     * @return invoker
     */
    @Adaptive({Constants.PROXY_KEY})
    <T> Invoker<T> getInvoker(T proxy, Class<T> type, URL url) throws RpcException;

}


public static final String PROXY_KEY = "proxy";