Dubbo源码-08-Exchanger

一 接口声明

@SPI(HeaderExchanger.NAME)
public interface Exchanger {

    /**
     * bind.
     *
     * @param url
     * @param handler
     * @return message server
     */
    @Adaptive({Constants.EXCHANGER_KEY})
    ExchangeServer bind(URL url, ExchangeHandler handler) throws RemotingException;

    /**
     * connect.
     *
     * @param url
     * @param handler
     * @return message channel
     */
    @Adaptive({Constants.EXCHANGER_KEY})
    ExchangeClient connect(URL url, ExchangeHandler handler) throws RemotingException;

}

默认实现使用header，HeaderExchanger，该实现没有标识@Adaptive

二 code生成

package com.alibaba.dubbo.remoting.exchange;

import com.alibaba.dubbo.common.extension.ExtensionLoader;

public class Exchanger$Adaptive implements com.alibaba.dubbo.remoting.exchange.Exchanger {
    public com.alibaba.dubbo.remoting.exchange.ExchangeClient connect(com.alibaba.dubbo.common.URL arg0, com.alibaba.dubbo.remoting.exchange.ExchangeHandler arg1) throws com.alibaba.dubbo.remoting.RemotingException {
        if (arg0 == null) throw new IllegalArgumentException("url == null");
        com.alibaba.dubbo.common.URL url = arg0;
        String extName = url.getParameter("exchanger", "header");
        if (extName == null)
            throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.remoting.exchange.Exchanger) name from url(" + url.toString() + ") use keys([exchanger])");
        com.alibaba.dubbo.remoting.exchange.Exchanger extension = (com.alibaba.dubbo.remoting.exchange.Exchanger) ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.remoting.exchange.Exchanger.class).getExtension(extName);
        return extension.connect(arg0, arg1);
    }

    public com.alibaba.dubbo.remoting.exchange.ExchangeServer bind(com.alibaba.dubbo.common.URL arg0, com.alibaba.dubbo.remoting.exchange.ExchangeHandler arg1) throws com.alibaba.dubbo.remoting.RemotingException {
        if (arg0 == null) throw new IllegalArgumentException("url == null");
        com.alibaba.dubbo.common.URL url = arg0;
        String extName = url.getParameter("exchanger", "header");
        if (extName == null)
            throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.remoting.exchange.Exchanger) name from url(" + url.toString() + ") use keys([exchanger])");
        com.alibaba.dubbo.remoting.exchange.Exchanger extension = (com.alibaba.dubbo.remoting.exchange.Exchanger) ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.remoting.exchange.Exchanger.class).getExtension(extName);
        return extension.bind(arg0, arg1);
    }
}

三 实现

HeaderExchanger

1 生产者导出服务

@Override
    public ExchangeServer bind(URL url, ExchangeHandler handler) throws RemotingException {
        /**
         * url
         *     - dubbo://192.168.0.11:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=native-provider&bind.ip=192.168.0.11&bind.port=20880&channel.readonly.sent=true&codec=dubbo&dubbo=2.0.2&generic=false&heartbeat=60000&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=35700&qos.port=22222&side=provider&timestamp=1669554921457
         */
        return new HeaderExchangeServer(Transporters.bind(url, new DecodeHandler(new HeaderExchangeHandler(handler))));
    }

public static Server bind(URL url, ChannelHandler... handlers) throws RemotingException {
        if (url == null) {
            throw new IllegalArgumentException("url == null");
        }
        if (handlers == null || handlers.length == 0) {
            throw new IllegalArgumentException("handlers == null");
        }
        ChannelHandler handler;
        if (handlers.length == 1) {
            handler = handlers[0];
        } else {
            handler = new ChannelHandlerDispatcher(handlers);
        }
        /**
         * url
         *     - dubbo://192.168.0.11:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=native-provider&bind.ip=192.168.0.11&bind.port=20880&channel.readonly.sent=true&codec=dubbo&dubbo=2.0.2&generic=false&heartbeat=60000&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=36435&qos.port=22222&side=provider&timestamp=1669555941396
         * 自适应
         *     - @SPI指定默认实现是netty
         *     - 自适应扩展点优先级
         *         - URL中配置server
         *         - URL中配置transporter
         * 默认实现是NettyTransporter
         */
        return getTransporter().bind(url, handler);
    }

public static Transporter getTransporter() {
        return ExtensionLoader.getExtensionLoader(Transporter.class).getAdaptiveExtension();
    }

跟进到NettyTransporter

2 消费者引用服务

// HeaderExchanger.java
@Override
    public ExchangeClient connect(URL url, ExchangeHandler handler) throws RemotingException {
        return new HeaderExchangeClient(Transporters.connect(url, new DecodeHandler(new HeaderExchangeHandler(handler))), true);
    }

// Transporters.java
public static Client connect(URL url, ChannelHandler... handlers) throws RemotingException {
        if (url == null) {
            throw new IllegalArgumentException("url == null");
        }
        ChannelHandler handler;
        if (handlers == null || handlers.length == 0) {
            handler = new ChannelHandlerAdapter();
        } else if (handlers.length == 1) {
            handler = handlers[0];
        } else {
            handler = new ChannelHandlerDispatcher(handlers);
        }
        return getTransporter().connect(url, handler);
    }

// Transporters.java
public static Transporter getTransporter() {
        return ExtensionLoader.getExtensionLoader(Transporter.class).getAdaptiveExtension();
    }

跟进到NettyTransporter