546 lines
22 KiB
Java
546 lines
22 KiB
Java
/*
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* Copyright 2012 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.channel;
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import io.netty.buffer.ByteBuf;
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import io.netty.util.concurrent.EventExecutor;
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import java.net.SocketAddress;
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import java.nio.ByteBuffer;
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import java.nio.channels.SocketChannel;
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import java.util.List;
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import java.util.Map;
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import java.util.NoSuchElementException;
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/**
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* A list of {@link ChannelHandler}s which handles or intercepts inbound events and outbound operations of a
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* {@link Channel}. {@link ChannelPipeline} implements an advanced form of the
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* <a href="http://www.oracle.com/technetwork/java/interceptingfilter-142169.html">Intercepting Filter</a> pattern
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* to give a user full control over how an event is handled and how the {@link ChannelHandler}s in a pipeline
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* interact with each other.
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*
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* <h3>Creation of a pipeline</h3>
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*
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* Each channel has its own pipeline and it is created automatically when a new channel is created.
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*
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* <h3>How an event flows in a pipeline</h3>
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*
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* The following diagram describes how I/O events are processed by {@link ChannelHandler}s in a {@link ChannelPipeline}
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* typically. An I/O event is handled by a {@link ChannelHandler} (which may handle inbound or / and outbound events)
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* and be forwarded to its closest handler by calling the event propagation methods defined in
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* {@link ChannelHandlerContext}, such as {@link ChannelHandlerContext#fireChannelRead(Object)} and
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* {@link ChannelHandlerContext#write(Object)}.
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*
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* <pre>
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* I/O Request
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* via {@link Channel} or
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* {@link ChannelHandlerContext}
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* |
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* +---------------------------------------------------+---------------+
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* | ChannelPipeline | |
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* | \|/ |
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* | +---------------------+ +-----------+----------+ |
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* | | Inbound Handler N | | Outbound Handler 1 | |
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* | +----------+----------+ +-----------+----------+ |
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* | /|\ | |
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* | | \|/ |
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* | +----------+----------+ +-----------+----------+ |
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* | | Inbound Handler N-1 | | Outbound Handler 2 | |
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* | +----------+----------+ +-----------+----------+ |
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* | /|\ . |
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* | . . |
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* | ChannelHandlerContext.fireIN_EVT() ChannelHandlerContext.OUT_EVT()|
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* | [ method call] [method call] |
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* | . . |
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* | . \|/ |
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* | +----------+----------+ +-----------+----------+ |
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* | | Inbound Handler 2 | | Outbound Handler M-1 | |
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* | +----------+----------+ +-----------+----------+ |
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* | /|\ | |
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* | | \|/ |
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* | +----------+----------+ +-----------+----------+ |
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* | | Inbound Handler 1 | | Outbound Handler M | |
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* | +----------+----------+ +-----------+----------+ |
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* | /|\ | |
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* +---------------+-----------------------------------+---------------+
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* | \|/
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* +---------------+-----------------------------------+---------------+
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* | | | |
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* | [ Socket.read() ] [ Socket.write() ] |
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* | |
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* | Netty Internal I/O Threads (Transport Implementation) |
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* +-------------------------------------------------------------------+
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* </pre>
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* An inbound event is handled by the inbound handlers in the bottom-up direction as shown on the left side of the
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* diagram. An inbound handler usually handles the inbound data generated by the I/O thread on the bottom of the
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* diagram. The inbound data is often read from a remote peer via the actual input operation such as
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* {@link SocketChannel#read(ByteBuffer)}. If an inbound event goes beyond the top inbound handler, it is discarded
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* silently, or logged if it needs your attention.
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* <p>
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* An outbound event is handled by the outbound handler in the top-down direction as shown on the right side of the
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* diagram. An outbound handler usually generates or transforms the outbound traffic such as write requests.
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* If an outbound event goes beyond the bottom outbound handler, it is handled by an I/O thread associated with the
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* {@link Channel}. The I/O thread often performs the actual output operation such as
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* {@link SocketChannel#write(ByteBuffer)}.
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* <p>
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* For example, let us assume that we created the following pipeline:
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* <pre>
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* {@link ChannelPipeline} p = ...;
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* p.addLast("1", new InboundHandlerA());
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* p.addLast("2", new InboundHandlerB());
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* p.addLast("3", new OutboundHandlerA());
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* p.addLast("4", new OutboundHandlerB());
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* p.addLast("5", new InboundOutboundHandlerX());
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* </pre>
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* In the example above, the class whose name starts with {@code Inbound} means it is an inbound handler.
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* The class whose name starts with {@code Outbound} means it is a outbound handler.
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* <p>
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* In the given example configuration, the handler evaluation order is 1, 2, 3, 4, 5 when an event goes inbound.
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* When an event goes outbound, the order is 5, 4, 3, 2, 1. On top of this principle, {@link ChannelPipeline} skips
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* the evaluation of certain handlers to shorten the stack depth:
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* <ul>
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* <li>3 and 4 don't implement {@link ChannelInboundHandler}, and therefore the actual evaluation order of an inbound
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* event will be: 1, 2, and 5.</li>
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* <li>1 and 2 don't implement {@link ChannelOutboundHandler}, and therefore the actual evaluation order of a
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* outbound event will be: 5, 4, and 3.</li>
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* <li>If 5 implements both {@link ChannelInboundHandler} and {@link ChannelOutboundHandler}, the evaluation order of
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* an inbound and a outbound event could be 125 and 543 respectively.</li>
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* </ul>
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*
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* <h3>Forwarding an event to the next handler</h3>
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*
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* As you might noticed in the diagram shows, a handler has to invoke the event propagation methods in
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* {@link ChannelHandlerContext} to forward an event to its next handler. Those methods include:
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* <ul>
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* <li>Inbound event propagation methods:
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* <ul>
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* <li>{@link ChannelHandlerContext#fireChannelRegistered()}</li>
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* <li>{@link ChannelHandlerContext#fireChannelActive()}</li>
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* <li>{@link ChannelHandlerContext#fireChannelRead(Object)}</li>
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* <li>{@link ChannelHandlerContext#fireChannelReadComplete()}</li>
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* <li>{@link ChannelHandlerContext#fireExceptionCaught(Throwable)}</li>
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* <li>{@link ChannelHandlerContext#fireUserEventTriggered(Object)}</li>
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* <li>{@link ChannelHandlerContext#fireChannelWritabilityChanged()}</li>
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* <li>{@link ChannelHandlerContext#fireChannelInactive()}</li>
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* <li>{@link ChannelHandlerContext#fireChannelUnregistered()}</li>
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* </ul>
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* </li>
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* <li>Outbound event propagation methods:
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* <ul>
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* <li>{@link ChannelHandlerContext#bind(SocketAddress, ChannelPromise)}</li>
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* <li>{@link ChannelHandlerContext#connect(SocketAddress, SocketAddress, ChannelPromise)}</li>
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* <li>{@link ChannelHandlerContext#write(Object, ChannelPromise)}</li>
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* <li>{@link ChannelHandlerContext#flush()}</li>
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* <li>{@link ChannelHandlerContext#read()}</li>
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* <li>{@link ChannelHandlerContext#disconnect(ChannelPromise)}</li>
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* <li>{@link ChannelHandlerContext#close(ChannelPromise)}</li>
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* <li>{@link ChannelHandlerContext#deregister(ChannelPromise)}</li>
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* </ul>
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* </li>
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* </ul>
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*
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* and the following example shows how the event propagation is usually done:
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*
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* <pre>
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* public class MyInboundHandler implements {@link ChannelInboundHandler} {
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* {@code @Override}
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* public void channelActive({@link ChannelHandlerContext} ctx) {
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* System.out.println("Connected!");
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* ctx.fireChannelActive();
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* }
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* }
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*
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* public class MyOutboundHandler implements {@link ChannelOutboundHandler} {
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* {@code @Override}
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* public void close({@link ChannelHandlerContext} ctx, {@link ChannelPromise} promise) {
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* System.out.println("Closing ..");
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* ctx.close(promise);
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* }
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* }
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* </pre>
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*
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* <h3>Building a pipeline</h3>
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* <p>
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* A user is supposed to have one or more {@link ChannelHandler}s in a pipeline to receive I/O events (e.g. read) and
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* to request I/O operations (e.g. write and close). For example, a typical server will have the following handlers
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* in each channel's pipeline, but your mileage may vary depending on the complexity and characteristics of the
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* protocol and business logic:
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*
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* <ol>
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* <li>Protocol Decoder - translates binary data (e.g. {@link ByteBuf}) into a Java object.</li>
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* <li>Protocol Encoder - translates a Java object into binary data.</li>
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* <li>Business Logic Handler - performs the actual business logic (e.g. database access).</li>
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* </ol>
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*
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* and it could be represented as shown in the following example:
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*
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* <pre>
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* ...
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*
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* {@link ChannelPipeline} pipeline = ch.pipeline();
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*
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* pipeline.addLast("decoder", new MyProtocolDecoder());
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* pipeline.addLast("encoder", new MyProtocolEncoder());
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*
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* // If your business logic does block or take a lot of time you should offload the work to an extra
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* // {@link java.util.concurrent.Executor} to ensure you don't block the {@link EventLoop}.
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* pipeline.addLast("handler", new MyBusinessLogicHandler());
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* </pre>
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*
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* <h3>Thread safety</h3>
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* <p>
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* A {@link ChannelHandler} can be added or removed at any time because a {@link ChannelPipeline} is thread safe.
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* For example, you can insert an encryption handler when sensitive information is about to be exchanged, and remove it
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* after the exchange.
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*/
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public interface ChannelPipeline
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extends ChannelInboundInvoker, ChannelOutboundInvoker, Iterable<Map.Entry<String, ChannelHandler>> {
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/**
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* Inserts a {@link ChannelHandler} at the first position of this pipeline.
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*
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* @param name the name of the handler to insert first
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* @param handler the handler to insert first
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*
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* @throws IllegalArgumentException
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* if there's an entry with the same name already in the pipeline
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* @throws NullPointerException
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* if the specified handler is {@code null}
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*/
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ChannelPipeline addFirst(String name, ChannelHandler handler);
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/**
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* Appends a {@link ChannelHandler} at the last position of this pipeline.
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*
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* @param name the name of the handler to append
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* @param handler the handler to append
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*
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* @throws IllegalArgumentException
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* if there's an entry with the same name already in the pipeline
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* @throws NullPointerException
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* if the specified handler is {@code null}
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*/
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ChannelPipeline addLast(String name, ChannelHandler handler);
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/**
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* Inserts a {@link ChannelHandler} before an existing handler of this
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* pipeline.
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*
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* @param baseName the name of the existing handler
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* @param name the name of the handler to insert before
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* @param handler the handler to insert before
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*
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* @throws NoSuchElementException
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* if there's no such entry with the specified {@code baseName}
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* @throws IllegalArgumentException
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* if there's an entry with the same name already in the pipeline
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* @throws NullPointerException
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* if the specified baseName or handler is {@code null}
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*/
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ChannelPipeline addBefore(String baseName, String name, ChannelHandler handler);
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/**
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* Inserts a {@link ChannelHandler} after an existing handler of this
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* pipeline.
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*
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* @param baseName the name of the existing handler
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* @param name the name of the handler to insert after
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* @param handler the handler to insert after
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*
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* @throws NoSuchElementException
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* if there's no such entry with the specified {@code baseName}
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* @throws IllegalArgumentException
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* if there's an entry with the same name already in the pipeline
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* @throws NullPointerException
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* if the specified baseName or handler is {@code null}
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*/
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ChannelPipeline addAfter(String baseName, String name, ChannelHandler handler);
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/**
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* Inserts {@link ChannelHandler}s at the first position of this pipeline.
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*
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* @param handlers the handlers to insert first
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*
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*/
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ChannelPipeline addFirst(ChannelHandler... handlers);
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/**
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* Inserts {@link ChannelHandler}s at the last position of this pipeline.
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*
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* @param handlers the handlers to insert last
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*
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*/
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ChannelPipeline addLast(ChannelHandler... handlers);
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/**
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* Removes the specified {@link ChannelHandler} from this pipeline.
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*
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* @param handler the {@link ChannelHandler} to remove
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*
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* @throws NoSuchElementException
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* if there's no such handler in this pipeline
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* @throws NullPointerException
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* if the specified handler is {@code null}
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*/
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ChannelPipeline remove(ChannelHandler handler);
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/**
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* Removes the {@link ChannelHandler} with the specified name from this pipeline.
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*
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* @param name the name under which the {@link ChannelHandler} was stored.
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*
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* @return the removed handler
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*
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* @throws NoSuchElementException
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* if there's no such handler with the specified name in this pipeline
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* @throws NullPointerException
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* if the specified name is {@code null}
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*/
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ChannelHandler remove(String name);
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/**
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* Removes the {@link ChannelHandler} of the specified type from this pipeline.
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*
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* @param <T> the type of the handler
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* @param handlerType the type of the handler
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*
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* @return the removed handler
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*
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* @throws NoSuchElementException
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* if there's no such handler of the specified type in this pipeline
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* @throws NullPointerException
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* if the specified handler type is {@code null}
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*/
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<T extends ChannelHandler> T remove(Class<T> handlerType);
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/**
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* Removes the first {@link ChannelHandler} in this pipeline.
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*
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* @return the removed handler
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*
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* @throws NoSuchElementException
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* if this pipeline is empty
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*/
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ChannelHandler removeFirst();
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/**
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* Removes the last {@link ChannelHandler} in this pipeline.
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*
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* @return the removed handler
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*
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* @throws NoSuchElementException
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* if this pipeline is empty
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*/
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ChannelHandler removeLast();
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/**
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* Replaces the specified {@link ChannelHandler} with a new handler in this pipeline.
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*
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* @param oldHandler the {@link ChannelHandler} to be replaced
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* @param newName the name under which the replacement should be added
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* @param newHandler the {@link ChannelHandler} which is used as replacement
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*
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* @return itself
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* @throws NoSuchElementException
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* if the specified old handler does not exist in this pipeline
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* @throws IllegalArgumentException
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* if a handler with the specified new name already exists in this
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* pipeline, except for the handler to be replaced
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* @throws NullPointerException
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* if the specified old handler or new handler is
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* {@code null}
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*/
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ChannelPipeline replace(ChannelHandler oldHandler, String newName, ChannelHandler newHandler);
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/**
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* Replaces the {@link ChannelHandler} of the specified name with a new handler in this pipeline.
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*
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* @param oldName the name of the {@link ChannelHandler} to be replaced
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* @param newName the name under which the replacement should be added
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* @param newHandler the {@link ChannelHandler} which is used as replacement
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*
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* @return the removed handler
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*
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* @throws NoSuchElementException
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* if the handler with the specified old name does not exist in this pipeline
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* @throws IllegalArgumentException
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* if a handler with the specified new name already exists in this
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* pipeline, except for the handler to be replaced
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* @throws NullPointerException
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* if the specified old handler or new handler is
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* {@code null}
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*/
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ChannelHandler replace(String oldName, String newName, ChannelHandler newHandler);
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/**
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* Replaces the {@link ChannelHandler} of the specified type with a new handler in this pipeline.
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*
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* @param oldHandlerType the type of the handler to be removed
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* @param newName the name under which the replacement should be added
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* @param newHandler the {@link ChannelHandler} which is used as replacement
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*
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* @return the removed handler
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*
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* @throws NoSuchElementException
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* if the handler of the specified old handler type does not exist
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* in this pipeline
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* @throws IllegalArgumentException
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* if a handler with the specified new name already exists in this
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* pipeline, except for the handler to be replaced
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* @throws NullPointerException
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* if the specified old handler or new handler is
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* {@code null}
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*/
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<T extends ChannelHandler> T replace(Class<T> oldHandlerType, String newName,
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ChannelHandler newHandler);
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/**
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* Returns the first {@link ChannelHandler} in this pipeline.
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*
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* @return the first handler. {@code null} if this pipeline is empty.
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*/
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ChannelHandler first();
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/**
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* Returns the context of the first {@link ChannelHandler} in this pipeline.
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*
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* @return the context of the first handler. {@code null} if this pipeline is empty.
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*/
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ChannelHandlerContext firstContext();
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/**
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* Returns the last {@link ChannelHandler} in this pipeline.
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*
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* @return the last handler. {@code null} if this pipeline is empty.
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*/
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ChannelHandler last();
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/**
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* Returns the context of the last {@link ChannelHandler} in this pipeline.
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*
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* @return the context of the last handler. {@code null} if this pipeline is empty.
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*/
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ChannelHandlerContext lastContext();
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/**
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* Returns {@code true} if this {@link ChannelPipeline} is empty, which means no {@link ChannelHandler} is
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* present.
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*/
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default boolean isEmpty() {
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return lastContext() == null;
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}
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/**
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* Returns the {@link ChannelHandler} with the specified name in this
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* pipeline.
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*
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* @return the handler with the specified name.
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* {@code null} if there's no such handler in this pipeline.
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*/
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ChannelHandler get(String name);
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/**
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* Returns the {@link ChannelHandler} of the specified type in this
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* pipeline.
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*
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* @return the handler of the specified handler type.
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* {@code null} if there's no such handler in this pipeline.
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*/
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<T extends ChannelHandler> T get(Class<T> handlerType);
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/**
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* Returns the context object of the specified {@link ChannelHandler} in
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* this pipeline.
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*
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* @return the context object of the specified handler.
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* {@code null} if there's no such handler in this pipeline.
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*/
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ChannelHandlerContext context(ChannelHandler handler);
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/**
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* Returns the context object of the {@link ChannelHandler} with the
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* specified name in this pipeline.
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*
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* @return the context object of the handler with the specified name.
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* {@code null} if there's no such handler in this pipeline.
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*/
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ChannelHandlerContext context(String name);
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/**
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* Returns the context object of the {@link ChannelHandler} of the
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* specified type in this pipeline.
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*
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* @return the context object of the handler of the specified type.
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* {@code null} if there's no such handler in this pipeline.
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*/
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ChannelHandlerContext context(Class<? extends ChannelHandler> handlerType);
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|
|
/**
|
|
* 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<String> names();
|
|
|
|
/**
|
|
* Converts this pipeline into an ordered {@link Map} whose keys are
|
|
* handler names and whose values are handlers.
|
|
*/
|
|
Map<String, ChannelHandler> 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();
|
|
|
|
/**
|
|
* Returns the {@link EventExecutor} which is used by all {@link ChannelHandler}s in the pipeline.
|
|
*/
|
|
EventExecutor executor();
|
|
}
|