用来在服务响应返回到客户端之前进行额外处理。
一、定义Filter

package cn.edu.tju.config;

import org.apache.dubbo.rpc.Filter;
import org.apache.dubbo.rpc.Result;
import org.apache.dubbo.rpc.Invoker;
import org.apache.dubbo.rpc.Invocation;
import org.apache.dubbo.rpc.RpcException;
import org.apache.dubbo.rpc.AsyncRpcResult;

public class AppendedFilter implements Filter {

    @Override
    public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
        Result result= invoker.invoke(invocation);
        // Obtain the returned value
        Result appResponse = ((AsyncRpcResult) result).getAppResponse();
        // Appended value
        appResponse.setValue(appResponse.getValue()+"'s customized AppendedFilter");
        return result;
    }
}

二、SPI注入Filter

org.apache.dubbo.rpc.Filter的内容如下：

appended=cn.edu.tju.config.AppendedFilter

三、配置文件中指定Filter

server:
  port: 9953
spring:
  application:
    name: dubbosky
dubbo:
  application:
    name: dubbosky
  protocol:
    name: dubbo
    port: 28030
  registry:
    address: nacos://xx.xx.xx.xx:8848
  provider:
    filter: appended