com.alibaba.dubbo.rpc

Interface Protocol

All Known Implementing Classes:

AbstractProtocol, AbstractProxyProtocol, DubboProtocol, HessianProtocol, HttpProtocol, InjvmProtocol, MemcachedProtocol, MockProtocol, ProtocolFilterWrapper, ProtocolListenerWrapper, QosProtocolWrapper, RedisProtocol, RegistryProtocol, RestProtocol, RmiProtocol, ThriftProtocol, WebServiceProtocol

@SPI(value="dubbo")
public interface Protocol

Protocol. (API/SPI, Singleton, ThreadSafe)

Method Summary

Modifier and Type	Method and Description
void	destroy() Destroy protocol: 1.
<T> Exporter<T>	export(Invoker<T> invoker) Export service for remote invocation: 1.
int	getDefaultPort() Get default port when user doesn't config the port.
<T> Invoker<T>	refer(Class<T> type, URL url) Refer a remote service: 1.

Method Detail

getDefaultPort

int getDefaultPort()

Get default port when user doesn't config the port.

Returns:

default port

export

@Adaptive
<T> Exporter<T> export(Invoker<T> invoker)
                          throws RpcException

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

Type Parameters:

T - Service type

Parameters:

invoker - Service invoker

Returns:

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

refer

@Adaptive
<T> Invoker<T> refer(Class<T> type,
                               URL url)
                        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.

Type Parameters:

T - Service type

Parameters:

type - Service class

url - URL address for the remote service

Returns:

invoker service's local proxy

Throws:

RpcException - when there's any error while connecting to the service provider

destroy

void destroy()

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.