/*
* 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.Buf;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.MessageBuf;
import io.netty.util.concurrent.EventExecutorGroup;
import java.io.InputStream;
import java.io.OutputStream;
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 and outbount 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 the pipeline interact with each other.
*
* Creation of a pipeline
*
* For each new channel, a new pipeline iscreated and attached to the
* channel. Once attached, the coupling between the channel and the pipeline
* is permanent; the channel cannot attach another pipeline to it nor detach
* the current pipeline from it. All of this is handled for you and you not need
* to take care of this.
*
*
*
*
How an event flows in a pipeline
*
* The following diagram describes how I/O is processed by
* {@link ChannelHandler}s in a {@link ChannelPipeline} typically.
* A I/O-operation can be handled by either a {@link ChannelInboundHandler}
* or a {@link ChannelOutboundHandler} and be forwarded to the closest
* handler by calling either one of the methods defined in the
* {@link ChannelInboundInvoker} interface for inbound I/O or by one
* of the methods defined in the {@link ChannelOutboundInvoker} interface
* for outbound I/O. {@link ChannelPipeline} extends both of them.
*
*
* I/O Request
* via {@link Channel} or
* {@link ChannelHandlerContext}
* |
* +----------------------------------------------------+-----------------+
* | ChannelPipeline | |
* | \|/ |
* | +----------------------+ +-----------+------------+ |
* | | Inbound Handler N | | Outbound Handler 1 | |
* | +----------+-----------+ +-----------+------------+ |
* | /|\ | |
* | | \|/ |
* | +----------+-----------+ +-----------+------------+ |
* | | Inbound Handler N-1 | | Outbound Handler 2 | |
* | +----------+-----------+ +-----------+------------+ |
* | /|\ . |
* | . . |
* | [{@link ChannelInboundInvoker}] [{@link ChannelOutboundInvoker}()] |
* | [ 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 InputStream#read(byte[])}.
* If an inbound event goes beyond the top inbound handler, it is discarded
* silently.
*
* A outbound event is handled by the outbound handler in the top-down
* direction as shown on the right side of the diagram. A outbound handler
* usually generates or transforms the outbound traffic such as write requests.
* If a 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 OutputStream#write(byte[])}.
*
* 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, 2, and 5 don't implement {@link ChannelOutboundHandler}, and
* therefore the actual evaluation order of a outbound event will be:
* 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.
*
*
* 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.
* - ExecutionHandler - applies a thread model.
* - Business Logic Handler - performs the actual business logic
* (e.g. database access).
*
*
* and it could be represented as shown in the following example:
*
*
* {@link ChannelPipeline} pipeline = ...;
* pipeline.addLast("decoder", new MyProtocolDecoder());
* pipeline.addLast("encoder", new MyProtocolEncoder());
* pipeline.addLast("executor", new ExecutionHandler(...));
* pipeline.addLast("handler", new MyBusinessLogicHandler());
*
*
* 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> {
/**
* Return the bound {@link MessageBuf} of the first {@link ChannelInboundMessageHandler} in the
* {@link ChannelPipeline}. If no {@link ChannelInboundMessageHandler} exists in the {@link ChannelPipeline}
* it will throw a {@link UnsupportedOperationException}.
*
* This method can only be called from within the event-loop, otherwise it will throw an
* {@link IllegalStateException}.
*/
MessageBuf inboundMessageBuffer();
/**
* Return the bound {@link ByteBuf} of the first {@link ChannelInboundByteHandler} in the
* {@link ChannelPipeline}. If no {@link ChannelInboundByteHandler} exists in the {@link ChannelPipeline}
* it will throw a {@link UnsupportedOperationException}.
*
* This method can only be called from within the event-loop, otherwise it will throw an
* {@link IllegalStateException}.
*/
ByteBuf inboundByteBuffer();
/**
* Return the bound {@link MessageBuf} of the first {@link ChannelOutboundMessageHandler} in the
* {@link ChannelPipeline}. If no {@link ChannelOutboundMessageHandler} exists in the {@link ChannelPipeline}
* it will throw a {@link UnsupportedOperationException}.
*
* This method can only be called from within the event-loop, otherwise it will throw an
* {@link IllegalStateException}.
*/
MessageBuf outboundMessageBuffer();
/**
* Return the bound {@link ByteBuf} of the first {@link ChannelOutboundByteHandler} in the
* {@link ChannelPipeline}. If no {@link ChannelOutboundByteHandler} exists in the {@link ChannelPipeline}
* it will throw a {@link UnsupportedOperationException}.
*
* This method can only be called from within the event-loop, otherwise it will throw an
* {@link IllegalStateException}.
*/
ByteBuf outboundByteBuffer();
/**
* 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 name or 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 name or 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 name or 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 name or 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, name, 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, name, 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, name, 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, name, or handler is {@code null}
*/
ChannelPipeline addAfter(EventExecutorGroup group, String baseName, String name, ChannelHandler handler);
/**
* Inserts a {@link ChannelHandler}s at the first position of this pipeline.
*
* @param handlers the handlers to insert first
*
*/
ChannelPipeline addFirst(ChannelHandler... handlers);
/**
* Inserts a {@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 a {@link ChannelHandler}s at the last position of this pipeline.
*
* @param handlers the handlers to insert last
*
*/
ChannelPipeline addLast(ChannelHandler... handlers);
/**
* Inserts a {@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.
* All the remaining content in the {@link Buf) (if any) of the
* {@link ChannelHandler} will be discarded.
*
* @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 specified {@link ChannelHandler} from this pipeline
* and transfer the content of its {@link Buf} to the next
* {@link ChannelHandler} in the {@link ChannelPipeline}.
*
* @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 removeAndForward(ChannelHandler handler);
/**
* Removes the {@link ChannelHandler} with the specified name from this
* pipeline. All the remaining content in the {@link Buf) (if any) of the
* {@link ChannelHandler} will be discarded.
*
* @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} with the specified name from this
* pipeline and transfer the content of its {@link Buf} to the next
* {@link ChannelHandler} in the {@link ChannelPipeline}.
*
* @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 removeAndForward(String name);
/**
* Removes the {@link ChannelHandler} of the specified type from this
* pipeline. All the remaining content in the {@link Buf) (if any) of the {@link ChannelHandler}
* will be discarded.
*
*
* @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 {@link ChannelHandler} of the specified type from this
* pipeline and transfer the content of its {@link Buf} to the next
* {@link ChannelHandler} in the {@link ChannelPipeline}.
*
* @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 removeAndForward(Class handlerType);
/**
* Removes the first {@link ChannelHandler} in this pipeline.
*
* All the remaining content in the {@link Buf) (if any) of the {@link ChannelHandler}
* will be discarded.
*
* @return the removed handler
*
* @throws NoSuchElementException
* if this pipeline is empty
*/
ChannelHandler removeFirst();
/**
* Removes the last {@link ChannelHandler} in this pipeline.
*
* All the remaining content in the {@link Buf) (if any) of the {@link ChannelHandler}
* will be discarded.
*
* @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.
*
* All the remaining content in the {@link Buf) (if any) of the {@link ChannelHandler}
* will be discarded.
*
* @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, new name, or new handler is
* {@code null}
*/
ChannelPipeline replace(ChannelHandler oldHandler, String newName, ChannelHandler newHandler);
/**
* Replaces the specified {@link ChannelHandler} with a new handler in
* this pipeline and transfer the content of its {@link Buf} to the next
* {@link ChannelHandler} in the {@link ChannelPipeline}.
*
* @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, new name, or new handler is
* {@code null}
*/
ChannelPipeline replaceAndForward(ChannelHandler oldHandler, String newName, ChannelHandler newHandler);
/**
* Replaces the {@link ChannelHandler} of the specified name with a new
* handler in this pipeline.
*
* All the remaining content of the {@link Buf) (if any) of the to be replaced
* {@link ChannelHandler} will be discarded.
*
* @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 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, new name, or new handler is
* {@code null}
*/
ChannelHandler replace(String oldName, String newName, ChannelHandler newHandler);
/**
* Replaces the {@link ChannelHandler} of the specified name with a new
* handler in this pipeline and transfer the content of its {@link Buf} to the next
* {@link ChannelHandler} in the {@link ChannelPipeline}.
*
* @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, new name, or new handler is
* {@code null}
*/
ChannelHandler replaceAndForward(String oldName, String newName, ChannelHandler newHandler);
/**
* Replaces the {@link ChannelHandler} of the specified type with a new
* handler in this pipeline.
*
* All the remaining content of the {@link Buf) (if any) of the to be replaced
* {@link ChannelHandler} will be discarded.
*
* @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, new name, or new handler is
* {@code null}
*/
T replace(Class oldHandlerType, String newName, ChannelHandler newHandler);
/**
* Replaces the {@link ChannelHandler} of the specified type with a new
* handler in this pipeline and transfer the content of its {@link Buf} to the next
* {@link ChannelHandler} in the {@link ChannelPipeline}.
*
* @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, new name, or new handler is
* {@code null}
*/
T replaceAndForward(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 fireInboundBufferUpdated();
@Override
ChannelPipeline fireChannelReadSuspended();
}