88 lines
3.3 KiB
Java
88 lines
3.3 KiB
Java
/*
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* Copyright 2009 Red Hat, Inc.
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*
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* Red Hat licenses this file to you under the Apache License, version 2.0
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* (the "License"); you may not use this file except in compliance with the
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* 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 org.jboss.netty.channel;
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/**
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* Handles or intercepts a downstream {@link ChannelEvent}, and sends a
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* {@link ChannelEvent} to the next handler in a {@link ChannelPipeline}.
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* <p>
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* The most common use case of this interface is to intercept an I/O request
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* such as {@link Channel#write(Object)} and {@link Channel#close()}.
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*
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* <h3>{@link SimpleChannelDownstreamHandler}</h3>
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* <p>
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* In most cases, you will get to use a {@link SimpleChannelDownstreamHandler}
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* to implement a downstream handler because it provides an individual handler
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* method for each event type. You might want to implement this interface
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* directly though if you want to handle various types of events in more
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* generic way.
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*
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* <h3>Firing an event to the next handler</h3>
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* <p>
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* You can forward the received event downstream or upstream. In most cases,
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* {@link ChannelDownstreamHandler} will send the event downstream
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* (i.e. outbound) although it is legal to send the event upstream (i.e. inbound):
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*
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* <pre>
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* // Sending the event downstream (outbound)
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* void handleDownstream({@link ChannelHandlerContext} ctx, {@link ChannelEvent} e) throws Exception {
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* ...
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* ctx.sendDownstream(e);
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* ...
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* }
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*
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* // Sending the event upstream (inbound)
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* void handleDownstream({@link ChannelHandlerContext} ctx, {@link ChannelEvent} e) throws Exception {
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* ...
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* ctx.sendUpstream(new {@link UpstreamChannelStateEvent}(...));
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* ...
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* }
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* </pre>
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*
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* <h4>Using the helper class to send an event</h4>
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* <p>
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* You will also find various helper methods in {@link Channels} to be useful
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* to generate and send an artificial or manipulated event.
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*
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* <h3>State management</h3>
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*
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* Please refer to {@link ChannelHandler}.
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*
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* <h3>Thread safety</h3>
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* <p>
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* {@link #handleDownstream(ChannelHandlerContext, ChannelEvent) handleDownstream}
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* may be invoked by more than one thread simultaneously. If the handler
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* accesses a shared resource or stores stateful information, you might need
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* proper synchronization in the handler implementation.
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*
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* @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
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* @author <a href="http://gleamynode.net/">Trustin Lee</a>
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*
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* @version $Rev: 2122 $, $Date: 2010-02-02 11:00:04 +0900 (Tue, 02 Feb 2010) $
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*
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* @apiviz.exclude ^org\.jboss\.netty\.handler\..*$
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*/
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public interface ChannelDownstreamHandler extends ChannelHandler {
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/**
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* Handles the specified downstream event.
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*
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* @param ctx the context object for this handler
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* @param e the downstream event to process or intercept
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*/
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void handleDownstream(ChannelHandlerContext ctx, ChannelEvent e) throws Exception;
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}
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