/*
* Copyright 2012 The Netty Project
*
* The Netty Project 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 io.netty.channel;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufAllocator;
import io.netty.util.Attribute;
import io.netty.util.AttributeKey;
import io.netty.util.AttributeMap;
import io.netty.util.concurrent.EventExecutor;
import io.netty.util.concurrent.FutureListener;
import java.net.ConnectException;
import java.net.SocketAddress;
import java.nio.channels.Channels;
/**
* Enables a {@link ChannelHandler} to interact with its {@link ChannelPipeline}
* and other handlers. A handler can notify the next {@link ChannelHandler} in the {@link ChannelPipeline},
* modify the {@link ChannelPipeline} it belongs to dynamically.
*
* <h3>Notify</h3>
*
* You can notify the closest handler in the
* same {@link ChannelPipeline} by calling one of the various methods provided here.
* Please refer to {@link ChannelPipeline} to understand how an event flows.
*
* <h3>Modifying a pipeline</h3>
*
* You can get the {@link ChannelPipeline} your handler belongs to by calling
* {@link #pipeline()}. A non-trivial application could insert, remove, or
* replace handlers in the pipeline dynamically at runtime.
*
* <h3>Retrieving for later use</h3>
*
* You can keep the {@link ChannelHandlerContext} for later use, such as
* triggering an event outside the handler methods, even from a different thread.
* <pre>
* public class MyHandler extends {@link ChannelDuplexHandler} {
*
* <b>private {@link ChannelHandlerContext} ctx;</b>
*
* public void beforeAdd({@link ChannelHandlerContext} ctx) {
* <b>this.ctx = ctx;</b>
* }
*
* public void login(String username, password) {
* ctx.write(new LoginMessage(username, password));
* }
* ...
* }
* </pre>
*
* <h3>Storing stateful information</h3>
*
* {@link #attr(AttributeKey)} allow you to
* store and access stateful information that is related with a handler and its
* context. Please refer to {@link ChannelHandler} to learn various recommended
* ways to manage stateful information.
*
* <h3>A handler can have more than one context</h3>
*
* Please note that a {@link ChannelHandler} instance can be added to more than
* one {@link ChannelPipeline}. It means a single {@link ChannelHandler}
* instance can have more than one {@link ChannelHandlerContext} and therefore
* the single instance can be invoked with different
* {@link ChannelHandlerContext}s if it is added to one or more
* {@link ChannelPipeline}s more than once.
* <p>
* For example, the following handler will have as many independent {@link AttributeKey}s
* as how many times it is added to pipelines, regardless if it is added to the
* same pipeline multiple times or added to different pipelines multiple times:
* <pre>
* public class FactorialHandler extends {@link ChannelInboundHandlerAdapter}<{@link Integer}> {
*
* private final {@link AttributeKey}<{@link Integer}> counter =
* new {@link AttributeKey}<{@link Integer}>("counter");
*
* // This handler will receive a sequence of increasing integers starting
* // from 1.
* {@code @Override}
* public void channelRead({@link ChannelHandlerContext} ctx, {@link Integer} integer) {
* {@link Attribute}<{@link Integer}> attr = ctx.getAttr(counter);
* Integer a = ctx.getAttr(counter).get();
*
* if (a == null) {
* a = 1;
* }
*
* attr.set(a * integer));
* }
* }
*
* // Different context objects are given to "f1", "f2", "f3", and "f4" even if
* // they refer to the same handler instance. Because the FactorialHandler
* // stores its state in a context object (as an (using an {@link AttributeKey}), the factorial is
* // calculated correctly 4 times once the two pipelines (p1 and p2) are active.
* FactorialHandler fh = new FactorialHandler();
*
* {@link ChannelPipeline} p1 = {@link Channels}.pipeline();
* p1.addLast("f1", fh);
* p1.addLast("f2", fh);
*
* {@link ChannelPipeline} p2 = {@link Channels}.pipeline();
* p2.addLast("f3", fh);
* p2.addLast("f4", fh);
* </pre>
*
* <h3>Additional resources worth reading</h3>
* <p>
* Please refer to the {@link ChannelHandler}, and
* {@link ChannelPipeline} to find out more about inbound and outbound operations,
* what fundamental differences they have, how they flow in a pipeline, and how to handle
* the operation in your application.
*/
public interface ChannelHandlerContext
extends AttributeMap {
/**
* Return the {@link Channel} which is bound to the {@link ChannelHandlerContext}.
*/
Channel channel();
/**
* The {@link EventExecutor} that is used to dispatch the events. This can also be used to directly
* submit tasks that get executed in the event loop. For more information please refer to the
* {@link EventExecutor} javadoc.
*/
EventExecutor executor();
/**
* The unique name of the {@link ChannelHandlerContext}.The name was used when then {@link ChannelHandler}
* was added to the {@link ChannelPipeline}. This name can also be used to access the registered
* {@link ChannelHandler} from the {@link ChannelPipeline}.
*/
String name();
/**
* The {@link ChannelHandler} that is bound this {@link ChannelHandlerContext}.
*/
ChannelHandler handler();
/**
* Return {@code true} if the {@link ChannelHandler} which belongs to this {@link ChannelHandler} was removed
* from the {@link ChannelPipeline}. Note that this method is only meant to be called from with in the
* {@link EventLoop}.
*/
boolean isRemoved();
/**
* A {@link Channel} was registered to its {@link EventLoop}.
*
* This will result in having the {@link ChannelInboundHandler#channelRegistered(ChannelHandlerContext)} method
* called of the next {@link ChannelInboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelHandlerContext fireChannelRegistered();
/**
* A {@link Channel} was unregistered from its {@link EventLoop}.
*
* This will result in having the {@link ChannelInboundHandler#channelUnregistered(ChannelHandlerContext)} method
* called of the next {@link ChannelInboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelHandlerContext fireChannelUnregistered();
/**
* A {@link Channel} is active now, which means it is connected.
*
* This will result in having the {@link ChannelInboundHandler#channelActive(ChannelHandlerContext)} method
* called of the next {@link ChannelInboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelHandlerContext fireChannelActive();
/**
* A {@link Channel} is inactive now, which means it is closed.
*
* This will result in having the {@link ChannelInboundHandler#channelInactive(ChannelHandlerContext)} method
* called of the next {@link ChannelInboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelHandlerContext fireChannelInactive();
/**
* A {@link Channel} received an {@link Throwable} in one of its inbound operations.
*
* This will result in having the {@link ChannelInboundHandler#exceptionCaught(ChannelHandlerContext, Throwable)}
* method called of the next {@link ChannelInboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelHandlerContext fireExceptionCaught(Throwable cause);
/**
* A {@link Channel} received an user defined event.
*
* This will result in having the {@link ChannelInboundHandler#userEventTriggered(ChannelHandlerContext, Object)}
* method called of the next {@link ChannelInboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelHandlerContext fireUserEventTriggered(Object event);
/**
* A {@link Channel} received a message.
*
* This will result in having the {@link ChannelInboundHandler#channelRead(ChannelHandlerContext, Object)}
* method called of the next {@link ChannelInboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelHandlerContext fireChannelRead(Object msg);
/**
* Triggers an {@link ChannelInboundHandler#channelReadComplete(ChannelHandlerContext)}
* event to the next {@link ChannelInboundHandler} in the {@link ChannelPipeline}.
*/
ChannelHandlerContext fireChannelReadComplete();
/**
* Triggers an {@link ChannelInboundHandler#channelWritabilityChanged(ChannelHandlerContext)}
* event to the next {@link ChannelInboundHandler} in the {@link ChannelPipeline}.
*/
ChannelHandlerContext fireChannelWritabilityChanged();
/**
* Request to bind to the given {@link SocketAddress} and notify the {@link ChannelFuture} once the operation
* completes, either because the operation was successful or because of an error.
* <p>
* This will result in having the
* {@link ChannelOutboundHandler#bind(ChannelHandlerContext, SocketAddress, ChannelPromise)} method
* called of the next {@link ChannelOutboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelFuture bind(SocketAddress localAddress);
/**
* Request to connect to the given {@link SocketAddress} and notify the {@link ChannelFuture} once the operation
* completes, either because the operation was successful or because of an error.
* <p>
* If the connection fails because of a connection timeout, the {@link ChannelFuture} will get failed with
* a {@link ConnectTimeoutException}. If it fails because of connection refused a {@link ConnectException}
* will be used.
* <p>
* This will result in having the
* {@link ChannelOutboundHandler#connect(ChannelHandlerContext, SocketAddress, SocketAddress, ChannelPromise)}
* method called of the next {@link ChannelOutboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelFuture connect(SocketAddress remoteAddress);
/**
* Request to connect to the given {@link SocketAddress} while bind to the localAddress and notify the
* {@link ChannelFuture} once the operation completes, either because the operation was successful or because of
* an error.
* <p>
* This will result in having the
* {@link ChannelOutboundHandler#connect(ChannelHandlerContext, SocketAddress, SocketAddress, ChannelPromise)}
* method called of the next {@link ChannelOutboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelFuture connect(SocketAddress remoteAddress, SocketAddress localAddress);
/**
* Request to disconnect from the remote peer and notify the {@link ChannelFuture} once the operation completes,
* either because the operation was successful or because of an error.
* <p>
* This will result in having the
* {@link ChannelOutboundHandler#disconnect(ChannelHandlerContext, ChannelPromise)}
* method called of the next {@link ChannelOutboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelFuture disconnect();
/**
* Request to close the {@link Channel} and notify the {@link ChannelFuture} once the operation completes,
* either because the operation was successful or because of
* an error.
*
* After it is closed it is not possible to reuse it again.
* <p>
* This will result in having the
* {@link ChannelOutboundHandler#close(ChannelHandlerContext, ChannelPromise)}
* method called of the next {@link ChannelOutboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelFuture close();
/**
* Request to deregister from the previous assigned {@link EventExecutor} and notify the
* {@link ChannelFuture} once the operation completes, either because the operation was successful or because of
* an error.
* <p>
* This will result in having the
* {@link ChannelOutboundHandler#deregister(ChannelHandlerContext, ChannelPromise)}
* method called of the next {@link ChannelOutboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*
*/
ChannelFuture deregister();
/**
* Request to bind to the given {@link SocketAddress} and notify the {@link ChannelFuture} once the operation
* completes, either because the operation was successful or because of an error.
*
* The given {@link ChannelPromise} will be notified.
* <p>
* This will result in having the
* {@link ChannelOutboundHandler#bind(ChannelHandlerContext, SocketAddress, ChannelPromise)} method
* called of the next {@link ChannelOutboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelFuture bind(SocketAddress localAddress, ChannelPromise promise);
/**
* Request to connect to the given {@link SocketAddress} and notify the {@link ChannelFuture} once the operation
* completes, either because the operation was successful or because of an error.
*
* The given {@link ChannelFuture} will be notified.
*
* <p>
* If the connection fails because of a connection timeout, the {@link ChannelFuture} will get failed with
* a {@link ConnectTimeoutException}. If it fails because of connection refused a {@link ConnectException}
* will be used.
* <p>
* This will result in having the
* {@link ChannelOutboundHandler#connect(ChannelHandlerContext, SocketAddress, SocketAddress, ChannelPromise)}
* method called of the next {@link ChannelOutboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelFuture connect(SocketAddress remoteAddress, ChannelPromise promise);
/**
* Request to connect to the given {@link SocketAddress} while bind to the localAddress and notify the
* {@link ChannelFuture} once the operation completes, either because the operation was successful or because of
* an error.
*
* The given {@link ChannelPromise} will be notified and also returned.
* <p>
* This will result in having the
* {@link ChannelOutboundHandler#connect(ChannelHandlerContext, SocketAddress, SocketAddress, ChannelPromise)}
* method called of the next {@link ChannelOutboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelFuture connect(SocketAddress remoteAddress, SocketAddress localAddress, ChannelPromise promise);
/**
* Request to disconnect from the remote peer and notify the {@link ChannelFuture} once the operation completes,
* either because the operation was successful or because of an error.
*
* The given {@link ChannelPromise} will be notified.
* <p>
* This will result in having the
* {@link ChannelOutboundHandler#disconnect(ChannelHandlerContext, ChannelPromise)}
* method called of the next {@link ChannelOutboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelFuture disconnect(ChannelPromise promise);
/**
* Request to close the {@link Channel} and notify the {@link ChannelFuture} once the operation completes,
* either because the operation was successful or because of
* an error.
*
* After it is closed it is not possible to reuse it again.
* The given {@link ChannelPromise} will be notified.
* <p>
* This will result in having the
* {@link ChannelOutboundHandler#close(ChannelHandlerContext, ChannelPromise)}
* method called of the next {@link ChannelOutboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelFuture close(ChannelPromise promise);
/**
* Request to deregister from the previous assigned {@link EventExecutor} and notify the
* {@link ChannelFuture} once the operation completes, either because the operation was successful or because of
* an error.
*
* The given {@link ChannelPromise} will be notified.
* <p>
* This will result in having the
* {@link ChannelOutboundHandler#deregister(ChannelHandlerContext, ChannelPromise)}
* method called of the next {@link ChannelOutboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelFuture deregister(ChannelPromise promise);
/**
* Request to Read data from the {@link Channel} into the first inbound buffer, triggers an
* {@link ChannelInboundHandler#channelRead(ChannelHandlerContext, Object)} event if data was
* read, and triggers a
* {@link ChannelInboundHandler#channelReadComplete(ChannelHandlerContext) channelReadComplete} event so the
* handler can decide to continue reading. If there's a pending read operation already, this method does nothing.
* <p>
* This will result in having the
* {@link ChannelOutboundHandler#read(ChannelHandlerContext)}
* method called of the next {@link ChannelOutboundHandler} contained in the {@link ChannelPipeline} of the
* {@link Channel}.
*/
ChannelHandlerContext read();
/**
* Request to write a message via this {@link ChannelHandlerContext} through the {@link ChannelPipeline}.
* This method will not request to actual flush, so be sure to call {@link #flush()}
* once you want to request to flush all pending data to the actual transport.
*/
ChannelFuture write(Object msg);
/**
* Request to write a message via this {@link ChannelHandlerContext} through the {@link ChannelPipeline}.
* This method will not request to actual flush, so be sure to call {@link #flush()}
* once you want to request to flush all pending data to the actual transport.
*/
ChannelFuture write(Object msg, ChannelPromise promise);
/**
* Request to flush all pending messages via this ChannelOutboundInvoker.
*/
ChannelHandlerContext flush();
/**
* Shortcut for call {@link #write(Object, ChannelPromise)} and {@link #flush()}.
*/
ChannelFuture writeAndFlush(Object msg, ChannelPromise promise);
/**
* Shortcut for call {@link #write(Object)} and {@link #flush()}.
*/
ChannelFuture writeAndFlush(Object msg);
/**
* Return the assigned {@link ChannelPipeline}
*/
ChannelPipeline pipeline();
/**
* Return the assigned {@link ByteBufAllocator} which will be used to allocate {@link ByteBuf}s.
*/
ByteBufAllocator alloc();
/**
* Return a new {@link ChannelPromise}.
*/
ChannelPromise newPromise();
/**
* Return an new {@link ChannelProgressivePromise}
*/
ChannelProgressivePromise newProgressivePromise();
/**
* Create a new {@link ChannelFuture} which is marked as succeeded already. So {@link ChannelFuture#isSuccess()}
* will return {@code true}. All {@link FutureListener} added to it will be notified directly. Also
* every call of blocking methods will just return without blocking.
*/
ChannelFuture newSucceededFuture();
/**
* Create a new {@link ChannelFuture} which is marked as failed already. So {@link ChannelFuture#isSuccess()}
* will return {@code false}. All {@link FutureListener} added to it will be notified directly. Also
* every call of blocking methods will just return without blocking.
*/
ChannelFuture newFailedFuture(Throwable cause);
/**
* Return a special ChannelPromise which can be reused for different operations.
* <p>
* It's only supported to use
* it for {@link ChannelHandlerContext#write(Object, ChannelPromise)}.
* </p>
* <p>
* Be aware that the returned {@link ChannelPromise} will not support most operations and should only be used
* if you want to save an object allocation for every write operation. You will not be able to detect if the
* operation was complete, only if it failed as the implementation will call
* {@link ChannelPipeline#fireExceptionCaught(Throwable)} in this case.
* </p>
* <strong>Be aware this is an expert feature and should be used with care!</strong>
*/
ChannelPromise voidPromise();
}