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/*
* 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:
*
* https://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.util.concurrent.DefaultEventExecutorGroup;
import io.netty.util.concurrent.EventExecutorGroup;
import io.netty.util.concurrent.UnorderedThreadPoolEventExecutor;
import java.net.SocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SocketChannel;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.NoSuchElementException;
/**
* A list of {@link ChannelHandler}s which handles or intercepts inbound events and outbound operations of a
* {@link Channel}. {@link ChannelPipeline} implements an advanced form of the
* Intercepting Filter pattern
* to give a user full control over how an event is handled and how the {@link ChannelHandler}s in a pipeline
* interact with each other.
*
* Creation of a pipeline
*
* Each channel has its own pipeline and it is created automatically when a new channel is created.
*
* How an event flows in a pipeline
*
* The following diagram describes how I/O events are processed by {@link ChannelHandler}s in a {@link ChannelPipeline}
* typically. An I/O event is handled by either a {@link ChannelInboundHandler} or a {@link ChannelOutboundHandler}
* and be forwarded to its closest handler by calling the event propagation methods defined in
* {@link ChannelHandlerContext}, such as {@link ChannelHandlerContext#fireChannelRead(Object)} and
* {@link ChannelHandlerContext#write(Object)}.
*
*
* I/O Request
* via {@link Channel} or
* {@link ChannelHandlerContext}
* |
* +---------------------------------------------------+---------------+
* | ChannelPipeline | |
* | \|/ |
* | +---------------------+ +-----------+----------+ |
* | | Inbound Handler N | | Outbound Handler 1 | |
* | +----------+----------+ +-----------+----------+ |
* | /|\ | |
* | | \|/ |
* | +----------+----------+ +-----------+----------+ |
* | | Inbound Handler N-1 | | Outbound Handler 2 | |
* | +----------+----------+ +-----------+----------+ |
* | /|\ . |
* | . . |
* | ChannelHandlerContext.fireIN_EVT() ChannelHandlerContext.OUT_EVT()|
* | [ method call] [method call] |
* | . . |
* | . \|/ |
* | +----------+----------+ +-----------+----------+ |
* | | Inbound Handler 2 | | Outbound Handler M-1 | |
* | +----------+----------+ +-----------+----------+ |
* | /|\ | |
* | | \|/ |
* | +----------+----------+ +-----------+----------+ |
* | | Inbound Handler 1 | | Outbound Handler M | |
* | +----------+----------+ +-----------+----------+ |
* | /|\ | |
* +---------------+-----------------------------------+---------------+
* | \|/
* +---------------+-----------------------------------+---------------+
* | | | |
* | [ Socket.read() ] [ Socket.write() ] |
* | |
* | Netty Internal I/O Threads (Transport Implementation) |
* +-------------------------------------------------------------------+
*
* An inbound event is handled by the inbound handlers in the bottom-up direction as shown on the left side of the
* diagram. An inbound handler usually handles the inbound data generated by the I/O thread on the bottom of the
* diagram. The inbound data is often read from a remote peer via the actual input operation such as
* {@link SocketChannel#read(ByteBuffer)}. If an inbound event goes beyond the top inbound handler, it is discarded
* silently, or logged if it needs your attention.
*
* An outbound event is handled by the outbound handler in the top-down direction as shown on the right side of the
* diagram. An outbound handler usually generates or transforms the outbound traffic such as write requests.
* If an outbound event goes beyond the bottom outbound handler, it is handled by an I/O thread associated with the
* {@link Channel}. The I/O thread often performs the actual output operation such as
* {@link SocketChannel#write(ByteBuffer)}.
*
* For example, let us assume that we created the following pipeline:
*
* {@link ChannelPipeline} p = ...;
* p.addLast("1", new InboundHandlerA());
* p.addLast("2", new InboundHandlerB());
* p.addLast("3", new OutboundHandlerA());
* p.addLast("4", new OutboundHandlerB());
* p.addLast("5", new InboundOutboundHandlerX());
*
* In the example above, the class whose name starts with {@code Inbound} means it is an inbound handler.
* The class whose name starts with {@code Outbound} means it is a outbound handler.
*
* In the given example configuration, the handler evaluation order is 1, 2, 3, 4, 5 when an event goes inbound.
* When an event goes outbound, the order is 5, 4, 3, 2, 1. On top of this principle, {@link ChannelPipeline} skips
* the evaluation of certain handlers to shorten the stack depth:
*
* - 3 and 4 don't implement {@link ChannelInboundHandler}, and therefore the actual evaluation order of an inbound
* event will be: 1, 2, and 5.
* - 1 and 2 don't implement {@link ChannelOutboundHandler}, and therefore the actual evaluation order of a
* outbound event will be: 5, 4, and 3.
* - If 5 implements both {@link ChannelInboundHandler} and {@link ChannelOutboundHandler}, the evaluation order of
* an inbound and a outbound event could be 125 and 543 respectively.
*
*
* Forwarding an event to the next handler
*
* As you might noticed in the diagram shows, a handler has to invoke the event propagation methods in
* {@link ChannelHandlerContext} to forward an event to its next handler. Those methods include:
*
* - Inbound event propagation methods:
*
* - {@link ChannelHandlerContext#fireChannelRegistered()}
* - {@link ChannelHandlerContext#fireChannelActive()}
* - {@link ChannelHandlerContext#fireChannelRead(Object)}
* - {@link ChannelHandlerContext#fireChannelReadComplete()}
* - {@link ChannelHandlerContext#fireExceptionCaught(Throwable)}
* - {@link ChannelHandlerContext#fireUserEventTriggered(Object)}
* - {@link ChannelHandlerContext#fireChannelWritabilityChanged()}
* - {@link ChannelHandlerContext#fireChannelInactive()}
* - {@link ChannelHandlerContext#fireChannelUnregistered()}
*
*
* - Outbound event propagation methods:
*
* - {@link ChannelHandlerContext#bind(SocketAddress, ChannelPromise)}
* - {@link ChannelHandlerContext#connect(SocketAddress, SocketAddress, ChannelPromise)}
* - {@link ChannelHandlerContext#write(Object, ChannelPromise)}
* - {@link ChannelHandlerContext#flush()}
* - {@link ChannelHandlerContext#read()}
* - {@link ChannelHandlerContext#disconnect(ChannelPromise)}
* - {@link ChannelHandlerContext#close(ChannelPromise)}
* - {@link ChannelHandlerContext#deregister(ChannelPromise)}
*
*
*
*
* and the following example shows how the event propagation is usually done:
*
*
* public class MyInboundHandler extends {@link ChannelInboundHandlerAdapter} {
* {@code @Override}
* public void channelActive({@link ChannelHandlerContext} ctx) {
* System.out.println("Connected!");
* ctx.fireChannelActive();
* }
* }
*
* public class MyOutboundHandler extends {@link ChannelOutboundHandlerAdapter} {
* {@code @Override}
* public void close({@link ChannelHandlerContext} ctx, {@link ChannelPromise} promise) {
* System.out.println("Closing ..");
* ctx.close(promise);
* }
* }
*
*
* Building a pipeline
*
* A user is supposed to have one or more {@link ChannelHandler}s in a pipeline to receive I/O events (e.g. read) and
* to request I/O operations (e.g. write and close). For example, a typical server will have the following handlers
* in each channel's pipeline, but your mileage may vary depending on the complexity and characteristics of the
* protocol and business logic:
*
*
* - Protocol Decoder - translates binary data (e.g. {@link ByteBuf}) into a Java object.
* - Protocol Encoder - translates a Java object into binary data.
* - Business Logic Handler - performs the actual business logic (e.g. database access).
*
*
* and it could be represented as shown in the following example:
*
*
* static final {@link EventExecutorGroup} group = new {@link DefaultEventExecutorGroup}(16);
* ...
*
* {@link ChannelPipeline} pipeline = ch.pipeline();
*
* pipeline.addLast("decoder", new MyProtocolDecoder());
* pipeline.addLast("encoder", new MyProtocolEncoder());
*
* // Tell the pipeline to run MyBusinessLogicHandler's event handler methods
* // in a different thread than an I/O thread so that the I/O thread is not blocked by
* // a time-consuming task.
* // If your business logic is fully asynchronous or finished very quickly, you don't
* // need to specify a group.
* pipeline.addLast(group, "handler", new MyBusinessLogicHandler());
*
*
* Be aware that while using {@link DefaultEventLoopGroup} will offload the operation from the {@link EventLoop} it will
* still process tasks in a serial fashion per {@link ChannelHandlerContext} and so guarantee ordering. Due the ordering
* it may still become a bottle-neck. If ordering is not a requirement for your use-case you may want to consider using
* {@link UnorderedThreadPoolEventExecutor} to maximize the parallelism of the task execution.
*
* Thread safety
*
* A {@link ChannelHandler} can be added or removed at any time because a {@link ChannelPipeline} is thread safe.
* For example, you can insert an encryption handler when sensitive information is about to be exchanged, and remove it
* after the exchange.
*/
public interface ChannelPipeline
extends ChannelInboundInvoker, ChannelOutboundInvoker, Iterable> {
/**
* Inserts a {@link ChannelHandler} at the first position of this pipeline.
*
* @param name the name of the handler to insert first
* @param handler the handler to insert first
*
* @throws IllegalArgumentException
* if there's an entry with the same name already in the pipeline
* @throws NullPointerException
* if the specified handler is {@code null}
*/
ChannelPipeline addFirst(String name, ChannelHandler handler);
/**
* Inserts a {@link ChannelHandler} at the first position of this pipeline.
*
* @param group the {@link EventExecutorGroup} which will be used to execute the {@link ChannelHandler}
* methods
* @param name the name of the handler to insert first
* @param handler the handler to insert first
*
* @throws IllegalArgumentException
* if there's an entry with the same name already in the pipeline
* @throws NullPointerException
* if the specified handler is {@code null}
*/
ChannelPipeline addFirst(EventExecutorGroup group, String name, ChannelHandler handler);
/**
* Appends a {@link ChannelHandler} at the last position of this pipeline.
*
* @param name the name of the handler to append
* @param handler the handler to append
*
* @throws IllegalArgumentException
* if there's an entry with the same name already in the pipeline
* @throws NullPointerException
* if the specified handler is {@code null}
*/
ChannelPipeline addLast(String name, ChannelHandler handler);
/**
* Appends a {@link ChannelHandler} at the last position of this pipeline.
*
* @param group the {@link EventExecutorGroup} which will be used to execute the {@link ChannelHandler}
* methods
* @param name the name of the handler to append
* @param handler the handler to append
*
* @throws IllegalArgumentException
* if there's an entry with the same name already in the pipeline
* @throws NullPointerException
* if the specified handler is {@code null}
*/
ChannelPipeline addLast(EventExecutorGroup group, String name, ChannelHandler handler);
/**
* Inserts a {@link ChannelHandler} before an existing handler of this
* pipeline.
*
* @param baseName the name of the existing handler
* @param name the name of the handler to insert before
* @param handler the handler to insert before
*
* @throws NoSuchElementException
* if there's no such entry with the specified {@code baseName}
* @throws IllegalArgumentException
* if there's an entry with the same name already in the pipeline
* @throws NullPointerException
* if the specified baseName or handler is {@code null}
*/
ChannelPipeline addBefore(String baseName, String name, ChannelHandler handler);
/**
* Inserts a {@link ChannelHandler} before an existing handler of this
* pipeline.
*
* @param group the {@link EventExecutorGroup} which will be used to execute the {@link ChannelHandler}
* methods
* @param baseName the name of the existing handler
* @param name the name of the handler to insert before
* @param handler the handler to insert before
*
* @throws NoSuchElementException
* if there's no such entry with the specified {@code baseName}
* @throws IllegalArgumentException
* if there's an entry with the same name already in the pipeline
* @throws NullPointerException
* if the specified baseName or handler is {@code null}
*/
ChannelPipeline addBefore(EventExecutorGroup group, String baseName, String name, ChannelHandler handler);
/**
* Inserts a {@link ChannelHandler} after an existing handler of this
* pipeline.
*
* @param baseName the name of the existing handler
* @param name the name of the handler to insert after
* @param handler the handler to insert after
*
* @throws NoSuchElementException
* if there's no such entry with the specified {@code baseName}
* @throws IllegalArgumentException
* if there's an entry with the same name already in the pipeline
* @throws NullPointerException
* if the specified baseName or handler is {@code null}
*/
ChannelPipeline addAfter(String baseName, String name, ChannelHandler handler);
/**
* Inserts a {@link ChannelHandler} after an existing handler of this
* pipeline.
*
* @param group the {@link EventExecutorGroup} which will be used to execute the {@link ChannelHandler}
* methods
* @param baseName the name of the existing handler
* @param name the name of the handler to insert after
* @param handler the handler to insert after
*
* @throws NoSuchElementException
* if there's no such entry with the specified {@code baseName}
* @throws IllegalArgumentException
* if there's an entry with the same name already in the pipeline
* @throws NullPointerException
* if the specified baseName or handler is {@code null}
*/
ChannelPipeline addAfter(EventExecutorGroup group, String baseName, String name, ChannelHandler handler);
/**
* Inserts {@link ChannelHandler}s at the first position of this pipeline.
*
* @param handlers the handlers to insert first
*
*/
ChannelPipeline addFirst(ChannelHandler... handlers);
/**
* Inserts {@link ChannelHandler}s at the first position of this pipeline.
*
* @param group the {@link EventExecutorGroup} which will be used to execute the {@link ChannelHandler}s
* methods.
* @param handlers the handlers to insert first
*
*/
ChannelPipeline addFirst(EventExecutorGroup group, ChannelHandler... handlers);
/**
* Inserts {@link ChannelHandler}s at the last position of this pipeline.
*
* @param handlers the handlers to insert last
*
*/
ChannelPipeline addLast(ChannelHandler... handlers);
/**
* Inserts {@link ChannelHandler}s at the last position of this pipeline.
*
* @param group the {@link EventExecutorGroup} which will be used to execute the {@link ChannelHandler}s
* methods.
* @param handlers the handlers to insert last
*
*/
ChannelPipeline addLast(EventExecutorGroup group, ChannelHandler... handlers);
/**
* Removes the specified {@link ChannelHandler} from this pipeline.
*
* @param handler the {@link ChannelHandler} to remove
*
* @throws NoSuchElementException
* if there's no such handler in this pipeline
* @throws NullPointerException
* if the specified handler is {@code null}
*/
ChannelPipeline remove(ChannelHandler handler);
/**
* Removes the {@link ChannelHandler} with the specified name from this pipeline.
*
* @param name the name under which the {@link ChannelHandler} was stored.
*
* @return the removed handler
*
* @throws NoSuchElementException
* if there's no such handler with the specified name in this pipeline
* @throws NullPointerException
* if the specified name is {@code null}
*/
ChannelHandler remove(String name);
/**
* Removes the {@link ChannelHandler} of the specified type from this pipeline.
*
* @param the type of the handler
* @param handlerType the type of the handler
*
* @return the removed handler
*
* @throws NoSuchElementException
* if there's no such handler of the specified type in this pipeline
* @throws NullPointerException
* if the specified handler type is {@code null}
*/
T remove(Class handlerType);
/**
* Removes the first {@link ChannelHandler} in this pipeline.
*
* @return the removed handler
*
* @throws NoSuchElementException
* if this pipeline is empty
*/
ChannelHandler removeFirst();
/**
* Removes the last {@link ChannelHandler} in this pipeline.
*
* @return the removed handler
*
* @throws NoSuchElementException
* if this pipeline is empty
*/
ChannelHandler removeLast();
/**
* Replaces the specified {@link ChannelHandler} with a new handler in this pipeline.
*
* @param oldHandler the {@link ChannelHandler} to be replaced
* @param newName the name under which the replacement should be added
* @param newHandler the {@link ChannelHandler} which is used as replacement
*
* @return itself
* @throws NoSuchElementException
* if the specified old handler does not exist in this pipeline
* @throws IllegalArgumentException
* if a handler with the specified new name already exists in this
* pipeline, except for the handler to be replaced
* @throws NullPointerException
* if the specified old handler or new handler is
* {@code null}
*/
ChannelPipeline replace(ChannelHandler oldHandler, String newName, ChannelHandler newHandler);
/**
* Replaces the {@link ChannelHandler} of the specified name with a new handler in this pipeline.
*
* @param oldName the name of the {@link ChannelHandler} to be replaced
* @param newName the name under which the replacement should be added
* @param newHandler the {@link ChannelHandler} which is used as replacement
*
* @return the removed handler
*
* @throws NoSuchElementException
* if the handler with the specified old name does not exist in this pipeline
* @throws IllegalArgumentException
* if a handler with the specified new name already exists in this
* pipeline, except for the handler to be replaced
* @throws NullPointerException
* if the specified old handler or new handler is
* {@code null}
*/
ChannelHandler replace(String oldName, String newName, ChannelHandler newHandler);
/**
* Replaces the {@link ChannelHandler} of the specified type with a new handler in this pipeline.
*
* @param oldHandlerType the type of the handler to be removed
* @param newName the name under which the replacement should be added
* @param newHandler the {@link ChannelHandler} which is used as replacement
*
* @return the removed handler
*
* @throws NoSuchElementException
* if the handler of the specified old handler type does not exist
* in this pipeline
* @throws IllegalArgumentException
* if a handler with the specified new name already exists in this
* pipeline, except for the handler to be replaced
* @throws NullPointerException
* if the specified old handler or new handler is
* {@code null}
*/
T replace(Class oldHandlerType, String newName,
ChannelHandler newHandler);
/**
* Returns the first {@link ChannelHandler} in this pipeline.
*
* @return the first handler. {@code null} if this pipeline is empty.
*/
ChannelHandler first();
/**
* Returns the context of the first {@link ChannelHandler} in this pipeline.
*
* @return the context of the first handler. {@code null} if this pipeline is empty.
*/
ChannelHandlerContext firstContext();
/**
* Returns the last {@link ChannelHandler} in this pipeline.
*
* @return the last handler. {@code null} if this pipeline is empty.
*/
ChannelHandler last();
/**
* Returns the context of the last {@link ChannelHandler} in this pipeline.
*
* @return the context of the last handler. {@code null} if this pipeline is empty.
*/
ChannelHandlerContext lastContext();
/**
* Returns the {@link ChannelHandler} with the specified name in this
* pipeline.
*
* @return the handler with the specified name.
* {@code null} if there's no such handler in this pipeline.
*/
ChannelHandler get(String name);
/**
* Returns the {@link ChannelHandler} of the specified type in this
* pipeline.
*
* @return the handler of the specified handler type.
* {@code null} if there's no such handler in this pipeline.
*/
T get(Class handlerType);
/**
* Returns the context object of the specified {@link ChannelHandler} in
* this pipeline.
*
* @return the context object of the specified handler.
* {@code null} if there's no such handler in this pipeline.
*/
ChannelHandlerContext context(ChannelHandler handler);
/**
* Returns the context object of the {@link ChannelHandler} with the
* specified name in this pipeline.
*
* @return the context object of the handler with the specified name.
* {@code null} if there's no such handler in this pipeline.
*/
ChannelHandlerContext context(String name);
/**
* Returns the context object of the {@link ChannelHandler} of the
* specified type in this pipeline.
*
* @return the context object of the handler of the specified type.
* {@code null} if there's no such handler in this pipeline.
*/
ChannelHandlerContext context(Class handlerType);
/**
* Returns the {@link Channel} that this pipeline is attached to.
*
* @return the channel. {@code null} if this pipeline is not attached yet.
*/
Channel channel();
/**
* Returns the {@link List} of the handler names.
*/
List names();
/**
* Converts this pipeline into an ordered {@link Map} whose keys are
* handler names and whose values are handlers.
*/
Map toMap();
@Override
ChannelPipeline fireChannelRegistered();
@Override
ChannelPipeline fireChannelUnregistered();
@Override
ChannelPipeline fireChannelActive();
@Override
ChannelPipeline fireChannelInactive();
@Override
ChannelPipeline fireExceptionCaught(Throwable cause);
@Override
ChannelPipeline fireUserEventTriggered(Object event);
@Override
ChannelPipeline fireChannelRead(Object msg);
@Override
ChannelPipeline fireChannelReadComplete();
@Override
ChannelPipeline fireChannelWritabilityChanged();
@Override
ChannelPipeline flush();
}