原文地址：http://blog.163.com/linfenliang@126/blog/static/127857195201467112958326/
Netty超时机制学习
技术点描述
ReadTimeoutHandler读取数据超时处理
WriteTimeoutHandler写数据超时处理
IdleStateHandler状态空闲处理
通过以上三种方式，可以轻松实现SOCKET长连接的心跳包机制。
另要注意的是这里所说的超时是指逻辑上的超时，而非TCP连接超时。
实现方案
ReadTimeoutHandler，WriteTimeoutHandler， IdleStateHandler这三种方式都是通过在数据处理管道ChannelPipelineFactory的实现类里配置相关代码来实现。
一般使用根据需求使用一种方式即可。
它主要使用Timer定时器用自定义的时间，去定时检测相应的状态，检测到后会根据选择的处理方式，是报错或回调指定的接口实现类处理。
参考源码包
主要包
IdleStateHandler 空闲状态的处理代码
源码：
/**
* Creates a new instance.
*
* @param timer
* the Timer that is used to trigger the scheduled event.
* The recommended Timer implementation is HashedWheelTimer.
* @param readerIdleTimeSeconds
* an IdleStateEvent whose state is IdleState.READER_IDLE
* will be triggered when no read was performed for the specified
* period of time. Specify 0 to disable.
* @param writerIdleTimeSeconds
* an IdleStateEvent whose state is IdleState.WRITER_IDLE
* will be triggered when no write was performed for the specified
* period of time. Specify {@code 0} to disable.
* @param allIdleTimeSeconds
* an IdleStateEvent whose state is IdleState.ALL_IDLE
* will be triggered when neither read nor write was performed
* for the specified period of time. Specify 0 to disable.
*/
public IdleStateHandler(
Timer timer,
int readerIdleTimeSeconds,
int writerIdleTimeSeconds,
int allIdleTimeSeconds) {
this(timer, readerIdleTimeSeconds, writerIdleTimeSeconds, allIdleTimeSeconds, TimeUnit.SECONDS);
}
ReadTimeoutHandler 读取数据超时的处理代码
源码：
/**
* Creates a new instance.
*
* @param timer
* the Timer that is used to trigger the scheduled event.
* The recommended Timer implementation is HashedWheelTimer.
* @param timeoutSeconds
* read timeout in seconds
*/
public ReadTimeoutHandler(Timer timer, int timeoutSeconds) {
this(timer, timeoutSeconds, TimeUnit.SECONDS);
}
WriteTimeoutHandler 写数据超时的处理代码
源码：
/**
* Creates a new instance.
*
* @param timer
* the Timer that is used to trigger the scheduled event.
* The recommended Timer implementation is HashedWheelTimer.
* @param timeoutSeconds
* write timeout in seconds
*/
public WriteTimeoutHandler(Timer timer, int timeoutSeconds) {
this(timer, timeoutSeconds, TimeUnit.SECONDS);
}
辅助包
IdleStateEvent 空闲事件的接口类
源码：
/**
* A ChannelEvent that is triggered when a Channel has been idle
* for a while.
* @apiviz.landmark
* @apiviz.has org.jboss.netty.handler.timeout.IdleState oneway - -
*/
public interface IdleStateEvent extends ChannelEvent {
/**
* Returns the detailed idle state.
*/
IdleState getState();
/**
* Returns the last time when I/O occurred in milliseconds.
*/
long getLastActivityTimeMillis();
}
DefaultIdleStateEvent空闲事件的实现类
IdleStateAwareChannelHandler 处理空闲事件的接口.
源码：
/**
* An extended SimpleChannelHandler that adds the handler method for
* an IdleStateEvent.
* @apiviz.uses org.jboss.netty.handler.timeout.IdleStateEvent
*/
public class IdleStateAwareChannelHandler extends SimpleChannelHandler {
/**
* Creates a new instance.
*/
public IdleStateAwareChannelHandler() {
super();
}
@Override
public void handleUpstream(ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
if (e instanceof IdleStateEvent) {
channelIdle(ctx, (IdleStateEvent) e);
} else {
super.handleUpstream(ctx, e);
}
}
/**
* Invoked when a Channel has been idle for a while.
*/
public void channelIdle(ChannelHandlerContext ctx, IdleStateEvent e) throws Exception {
ctx.sendUpstream(e);
}
}
IdleStateAwareChannelUpstreamHandler处理空闲事件的接口.
IdleState 定义了三种空闲状态的枚举类
源码：
/**
* An Enum that represents the idle state of a Channel.
*/
public enum IdleState {
/**
* No data was received for a while.
*/
READER_IDLE,
/**
* No data was sent for a while.
*/
WRITER_IDLE,
/**
* No data was either received or sent for a while.
*/
ALL_IDLE;
}
ReadTimeoutException 读取超时异常类
WriteTimeoutException 写数据超时异常类
TimeoutException 读取数据和写数据异常类的父类
Demo实现
以下是关于三种方式的关键代码实现讲解。
IdleStateHandler
//第一步,在服务启动类中设置数据处理管道.
...
bootstrap.setPipelineFactory(new TCPServerPipelineFactory());
...
//第二步,在数据处理管道实现类里配置空闲状态处理代码.
public class TCPServerPipelineFactory implements ChannelPipelineFactory {
@Override
public ChannelPipeline getPipeline() throws Exception {
// Create a default pipeline implementation.
ChannelPipeline pipeline = Channels.pipeline();
//设置空闲状态处理操作
pipeline.addLast("idlehandler", new IdleStateHandler(new HashedWheelTimer(), 10, 5 , 0));
pipeline.addLast("hearbeat", new Heartbeat());
pipeline.addLast("handler", new TCPServerHandler());
return pipeline;
}
//第三步,实现方式1：自定义IdleStateAwareChannelHandler的实现类,
//当Channel处理空闲状态时,会触发此方法.
public class Heartbeat extends IdleStateAwareChannelHandler {
@Override
public void channelIdle(ChannelHandlerContext ctx, IdleStateEvent e) throws Exception {
super.channelIdle(ctx, e);
if (e.getState() == IdleState.READER_IDLE){
byte[] test = " ac0bce0490007050006".getBytes();
ChannelBuffer channelBuffer = ChannelBuffers.buffer(test.length);
channelBuffer.writeBytes(upData);
//发送超时数据到终端.
e.getChannel().write(channelBuffer);
}
}
//第三步, 实现方式2：在扩展SimpleChannelHandler的handler类里,如下操作:
//记得注释掉第二步中的代码pipeline.addLast("hearbeat", new Heartbeat());
@Override
public void handleUpstream(ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
if (e instanceof IdleStateEvent) {
IdleStateEvent ise = (IdleStateEvent)e;
if (ise.getState() == IdleState.READER_IDLE){
byte[] test = "超时 ...".getBytes();
ChannelBuffer channelBuffer = ChannelBuffers.buffer(test.length);
channelBuffer.writeBytes(test);
//发送超时数据到终端.
ctx.getChannel().write(channelBuffer);
}
}
super.handleUpstream(ctx, e);
}
ReadTimeoutHandler
//第一步,在服务启动类中设置数据处理管道.
...
bootstrap.setPipelineFactory(new TCPServerPipelineFactory());
...
//第二步,在数据处理管道实现类里配置空闲状态处理代码.
public class TCPServerPipelineFactory implements ChannelPipelineFactory {
@Override
public ChannelPipeline getPipeline() throws Exception {
// Create a default pipeline implementation.
ChannelPipeline pipeline = Channels.pipeline();
//设置读取数据超时处理
pipeline.addLast("readTimeOut",new ReadTimeoutHandler(new HashedWheelTimer(),10));
pipeline.addLast("handler", new TCPServerHandler());
return pipeline;
}
//第三步, 在扩展SimpleChannelHandler的handler类里,如下操作:
@Override
public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
//对读取超时异常进行判断
if (e.getCause() instanceof ReadTimeoutException) {
byte[] test = "超时 ...".getBytes();
ChannelBuffer channelBuffer = ChannelBuffers.buffer(test.length);
channelBuffer.writeBytes(test);
ctx.getChannel().write(channelBuffer);
} else {
logger.log(Level.WARN, "Unexpected exception from downstream.",e.getCause());
}
}
WriteTimeoutHandler
略，原理同ReadTimeoutHandler。
Netty的超时机制
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转载自wangxiaoxu.iteye.com/blog/2174181
周排行