* The recommended way to create a new pipeline is to use the helper methods in * {@link Channels} rather than calling an individual implementation's * constructor: *
* import static io.netty.channel.{@link Channels}.*;
* {@link ChannelPipeline} pipeline = pipeline(); // same with Channels.pipeline()
*
*
*
* I/O Request
* via {@link Channel} or
* {@link ChannelHandlerContext}
* |
* +----------------------------------------+---------------+
* | ChannelPipeline | |
* | \|/ |
* | +----------------------+ +-----------+------------+ |
* | | Upstream Handler N | | Downstream Handler 1 | |
* | +----------+-----------+ +-----------+------------+ |
* | /|\ | |
* | | \|/ |
* | +----------+-----------+ +-----------+------------+ |
* | | Upstream Handler N-1 | | Downstream Handler 2 | |
* | +----------+-----------+ +-----------+------------+ |
* | /|\ . |
* | . . |
* | [ sendUpstream() ] [ sendDownstream() ] |
* | [ + INBOUND data ] [ + OUTBOUND data ] |
* | . . |
* | . \|/ |
* | +----------+-----------+ +-----------+------------+ |
* | | Upstream Handler 2 | | Downstream Handler M-1 | |
* | +----------+-----------+ +-----------+------------+ |
* | /|\ | |
* | | \|/ |
* | +----------+-----------+ +-----------+------------+ |
* | | Upstream Handler 1 | | Downstream Handler M | |
* | +----------+-----------+ +-----------+------------+ |
* | /|\ | |
* +-------------+--------------------------+---------------+
* | \|/
* +-------------+--------------------------+---------------+
* | | | |
* | [ Socket.read() ] [ Socket.write() ] |
* | |
* | Netty Internal I/O Threads (Transport Implementation) |
* +--------------------------------------------------------+
*
* An upstream event is handled by the upstream handlers in the bottom-up
* direction as shown on the left side of the diagram. An upstream 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 upstream event goes beyond the top upstream handler, it is discarded
* silently.
* * A downstream event is handled by the downstream handler in the top-down * direction as shown on the right side of the diagram. A downstream handler * usually generates or transforms the outbound traffic such as write requests. * If a downstream event goes beyond the bottom downstream 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 = {@link Channels}.pipeline();
* p.addLast("1", new UpstreamHandlerA());
* p.addLast("2", new UpstreamHandlerB());
* p.addLast("3", new DownstreamHandlerA());
* p.addLast("4", new DownstreamHandlerB());
* p.addLast("5", new UpstreamHandlerX());
*
* In the example above, the class whose name starts with {@code Upstream} means
* it is an upstream handler. The class whose name starts with
* {@code Downstream} means it is a downstream handler.
* * In the given example configuration, the handler evaluation order is 1, 2, 3, * 4, 5 when an event goes upstream. When an event goes downstream, 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: *
* 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: * *
* {@link ChannelPipeline} pipeline = {@link Channels#pipeline() Channels.pipeline()};
* pipeline.addLast("decoder", new MyProtocolDecoder());
* pipeline.addLast("encoder", new MyProtocolEncoder());
* pipeline.addLast("executor", new ExecutionHandler(...));
* pipeline.addLast("handler", new MyBusinessLogicHandler());
*
*
* * 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. * *
* Due to the internal implementation detail of the current default * {@link ChannelPipeline}, the following code does not work as expected if * FirstHandler is the last handler in the pipeline: *
* public class FirstHandler extends {@link SimpleChannelUpstreamHandler} {
*
* {@code @Override}
* public void messageReceived({@link ChannelHandlerContext} ctx, {@link MessageEvent} e) {
* // Remove this handler from the pipeline,
* ctx.getPipeline().remove(this);
* // And let SecondHandler handle the current event.
* ctx.getPipeline().addLast("2nd", new SecondHandler());
* ctx.sendUpstream(e);
* }
* }
*
* To implement the expected behavior, you have to add SecondHandler
* before the removal or make sure there is at least one more handler between
* FirstHandler and SecondHandler.
* @apiviz.landmark
* @apiviz.composedOf io.netty.channel.ChannelHandlerContext
* @apiviz.owns io.netty.channel.ChannelHandler
* @apiviz.uses io.netty.channel.ChannelSink - - sends events downstream
*/
public interface ChannelPipeline {
/**
* 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}
*/
void addFirst (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}
*/
void addLast (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}
*/
void addBefore(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}
*/
void addAfter (String baseName, String name, ChannelHandler handler);
/**
* Removes the specified {@link ChannelHandler} from this pipeline.
*
* @throws NoSuchElementException
* if there's no such handler in this pipeline
* @throws NullPointerException
* if the specified handler is {@code null}
*/
void remove(ChannelHandler handler);
/**
* Removes the {@link ChannelHandler} with the specified name from this
* pipeline.
*
* @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