消息派发扩展

<dubbo:protocol dispatcher="xxx" />
<!-- 缺省值设置，当<dubbo:protocol>没有配置dispatcher属性时，使用此配置 -->
<dubbo:provider dispatcher="xxx" />

src
 |-main
    |-java
        |-com
            |-xxx
                |-XxxDispatcher.java (实现Dispatcher接口)
    |-resources
        |-META-INF
            |-dubbo
                |-org.apache.dubbo.remoting.Dispatcher (纯文本文件，内容为：xxx=com.xxx.XxxDispatcher)

package com.xxx;
 
import org.apache.dubbo.remoting.Dispatcher;
 
public class XxxDispatcher implements Dispatcher {
    public Group lookup(URL url) {
        // ...
    }
}

xxx=com.xxx.XxxDispatcher