dubbo Protocol 源码
dubbo Protocol 代码
文件路径:/dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/Protocol.java
/*
* 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.ExtensionScope;
import org.apache.dubbo.common.extension.SPI;
import java.util.Collections;
import java.util.List;
/**
* RPC Protocol extension interface, which encapsulates the details of remote invocation. <br /><br />
*
* <p>Conventions:
*
* <li>
* When user invokes the 'invoke()' method in object that the method 'refer()' returns,
* the protocol needs to execute the 'invoke()' method of Invoker object that received by 'export()' method,
* which should have the same URL.
* </li>
*
* <li>
* Invoker that returned by 'refer()' is implemented by the protocol. The remote invocation request should be sent by that Invoker.
* </li>
*
* <li>
* The invoker that 'export()' receives will be implemented by framework. Protocol implementation should not care with that.
* </li>
*
* <p>Attentions:
*
* <li>
* The Protocol implementation does not care the transparent proxy. The invoker will be converted to business interface by other layer.
* </li>
*
* <li>
* The protocol doesn't need to be backed by TCP connection. It can also be backed by file sharing or inter-process communication.
* </li>
*
* (API/SPI, Singleton, ThreadSafe)
*/
@SPI(value = "dubbo", scope = ExtensionScope.FRAMEWORK)
public interface Protocol {
/**
* Get default port when user doesn't config the port.
*
* @return default port
*/
int getDefaultPort();
/**
* Export service for remote invocation: <br>
* 1. Protocol should record request source address after receive a request:
* RpcContext.getServerAttachment().setRemoteAddress();<br>
* 2. export() must be idempotent, that is, there's no difference between invoking once and invoking twice when
* export the same URL<br>
* 3. Invoker instance is passed in by the framework, protocol needs not to care <br>
*
* @param <T> 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
<T> Exporter<T> export(Invoker<T> invoker) throws RpcException;
/**
* Refer a remote service: <br>
* 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 <br>
* 2. It's protocol's responsibility to implement `Invoker` which's returned from `refer()`. Generally speaking,
* protocol sends remote request in the `Invoker` implementation. <br>
* 3. When there's check=false set in URL, the implementation must not throw exception but try to recover when
* connection fails.
*
* @param <T> 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
<T> Invoker<T> refer(Class<T> type, URL url) throws RpcException;
/**
* Destroy protocol: <br>
* 1. Cancel all services this protocol exports and refers <br>
* 2. Release all occupied resources, for example: connection, port, etc. <br>
* 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<ProtocolServer> getServers() {
return Collections.emptyList();
}
}
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