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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.dubbo.rpc;
import org.apache.dubbo.common.URL;
import org.apache.dubbo.common.extension.Adaptive;
import org.apache.dubbo.common.extension.SPI;
import java.util.Collections;
import java.util.List;
/**
* Protocol. (API/SPI, Singleton, ThreadSafe)
*/
@SPI("dubbo")
public interface Protocol {
/**
* Get default port when user doesn't config the port.
*
* @return default port
*/
int getDefaultPort();
/**
* Export service for remote invocation:
* 1. Protocol should record request source address after receive a request:
* RpcContext.getContext().setRemoteAddress();
* 2. export() must be idempotent, that is, there's no difference between invoking once and invoking twice when
* export the same URL
* 3. Invoker instance is passed in by the framework, protocol needs not to care
*
* @param Service type
* @param invoker Service invoker
* @return exporter reference for exported service, useful for unexport the service later
* @throws RpcException thrown when error occurs during export the service, for example: port is occupied
*/
@Adaptive
Exporter export(Invoker invoker) throws RpcException;
/**
* Refer a remote service:
* 1. When user calls `invoke()` method of `Invoker` object which's returned from `refer()` call, the protocol
* needs to correspondingly execute `invoke()` method of `Invoker` object
* 2. It's protocol's responsibility to implement `Invoker` which's returned from `refer()`. Generally speaking,
* protocol sends remote request in the `Invoker` implementation.
* 3. When there's check=false set in URL, the implementation must not throw exception but try to recover when
* connection fails.
*
* @param Service type
* @param type Service class
* @param url URL address for the remote service
* @return invoker service's local proxy
* @throws RpcException when there's any error while connecting to the service provider
*/
@Adaptive
Invoker refer(Class type, URL url) throws RpcException;
/**
* Destroy protocol:
* 1. Cancel all services this protocol exports and refers
* 2. Release all occupied resources, for example: connection, port, etc.
* 3. Protocol can continue to export and refer new service even after it's destroyed.
*/
void destroy();
/**
* Get all servers serving this protocol
*
* @return
*/
default List getServers() {
return Collections.emptyList();
}
}