Jetty基于NIO的方式处理请求

zhendeaini123

　　Jetty基于NIO的方式处理请求的类是SelectChannelConnector,该类同样继承AbstractLifeCycle类,SelectChannelConnector初始化的时候会调用AbstractLifeCycle类的start()方法,如下:

public final void start() throws Exception
{
synchronized (_lock)
{
try
{
if (_state == STARTED || _state == STARTING)
return;
setStarting();
doStart();
Log.debug("started {}",this);
setStarted();
}
catch (Exception e)
{
setFailed(e);
throw e;
}
catch (Error e)
{
setFailed(e);
throw e;
}
}
}
　　doStart()方法在SelectChannelConnector类中.如下:

   protected void doStart() throws Exception
{
_manager.setSelectSets(getAcceptors());//设置接收请求的线程个数,默认1个
_manager.setMaxIdleTime(getMaxIdleTime());
_manager.setLowResourcesConnections(getLowResourcesConnections());
_manager.setLowResourcesMaxIdleTime(getLowResourcesMaxIdleTime());
_manager.start();//初始化Selector
open();//初始化ServerSocketChannel
_manager.register(_acceptChannel);
super.doStart();
}
　　_manager类名为SelectorManager,open()方法如下:

    public void open() throws IOException
{
synchronized(this)
{
if (_acceptChannel == null)
{
// Create a new server socket
_acceptChannel = ServerSocketChannel.open();
// Bind the server socket to the local host and port
_acceptChannel.socket().setReuseAddress(getReuseAddress());
InetSocketAddress addr = getHost()==null?new InetSocketAddress(getPort()):new InetSocketAddress(getHost(),getPort());
_acceptChannel.socket().bind(addr,getAcceptQueueSize());
// Set to non blocking mode
_acceptChannel.configureBlocking(false);
}
}
}
　　super.doStart()方法如下:

protected void doStart() throws Exception
{
if (_server==null)
throw new IllegalStateException("No server");
// open listener port
open();//再一次调用open()方法,确保ServerSocketChannel启动,调用两次就能确保启动?
super.doStart();
if (_threadPool==null)
_threadPool=_server.getThreadPool();
if (_threadPool!=_server.getThreadPool() && (_threadPool instanceof LifeCycle))
((LifeCycle)_threadPool).start();
// Start selector thread
synchronized(this)
{
_acceptorThread=new Thread[getAcceptors()];
for (int i=0;i<_acceptorThread.length;i++)
{
if (!_threadPool.dispatch(new Acceptor(i)))//启动接受请求的线程
{
Log.warn("insufficient maxThreads configured for {}",this);
break;
}
}
}
Log.info("Started {}",this);
}
　　Acceptor线程的run()方法如下:

public void run()
{   
Thread current = Thread.currentThread();
String name;
synchronized(AbstractConnector.this)//设置当前线程的名字,是不是太复杂点
{
if (_acceptorThread==null)
return;
_acceptorThread[_acceptor]=current;
name =_acceptorThread[_acceptor].getName();
current.setName(name+" - Acceptor"+_acceptor+" "+AbstractConnector.this);
}
int old_priority=current.getPriority();
try
{
current.setPriority(old_priority-_acceptorPriorityOffset);
while (isRunning() && getConnection()!=null)//connector初始化并且ServerSocketChannel存在
{
try
{
accept(_acceptor);//处理收到的请求
}
catch(EofException e)
{
Log.ignore(e);
}
catch(IOException e)
{
Log.ignore(e);
}
catch(ThreadDeath e)
{
throw e;
}
catch(Throwable e)
{
Log.warn(e);
}
}
}
finally
{   
current.setPriority(old_priority);
current.setName(name);
synchronized(AbstractConnector.this)
{
if (_acceptorThread!=null)
_acceptorThread[_acceptor]=null;
}
}
}
　　accept(_acceptor)最终会调用SelectorManager.SelectSet.doSelect()方法,该方法比较复杂,简单来说就是每接受一个请求就注册到Selector上,并且用SelectChannelEndPoint类(本身也是一个线程)处理请求,SelectChannelEndPoint类的run()方法如下:

   public void run()
{
try
{
_connection.handle();
}
catch (ClosedChannelException e)
{
Log.ignore(e);
}
catch (EofException e)
{
Log.debug("EOF", e);
try{close();}
catch(IOException e2){Log.ignore(e2);}
}
catch (HttpException e)
{
Log.debug("BAD", e);
try{close();}
catch(IOException e2){Log.ignore(e2);}
}
catch (Throwable e)
{
Log.warn("handle failed", e);
try{close();}
catch(IOException e2){Log.ignore(e2);}
}
finally
{
undispatch();
}
}
　　_connection类的类名为HttpConnection,HttpConnection的handle()方法如下:

   public void handle() throws IOException
{
// Loop while more in buffer
boolean more_in_buffer = true; // assume true until proven otherwise
int no_progress = 0;
while (more_in_buffer)
{
try
{
synchronized (this)
{
if (_handling)
throw new IllegalStateException(); // TODO delete this
// check
_handling = true;
}
setCurrentConnection(this);
long io = 0;
Continuation continuation = _request.getContinuation();//得到RetryContinuation
if (continuation != null && continuation.isPending())
{
Log.debug("resume continuation {}",continuation);
if (_request.getMethod() == null)
throw new IllegalStateException();
handleRequest();//处理http请求,执行filter,servlet等
}
else//解析http请求
{
// If we are not ended then parse available
if (!_parser.isComplete())
io = _parser.parseAvailable();
// Do we have more generating to do?
// Loop here because some writes may take multiple steps and
// we need to flush them all before potentially blocking in
// the
// next loop.
while (_generator.isCommitted() && !_generator.isComplete())
{
long written = _generator.flush();
io += written;
if (written <= 0)
break;
if (_endp.isBufferingOutput())
_endp.flush();
}
// Flush buffers
if (_endp.isBufferingOutput())
{
_endp.flush();
if (!_endp.isBufferingOutput())
no_progress = 0;
}
if (io > 0)
no_progress = 0;
else if (no_progress++ >= 2)
return;
}
}
catch (HttpException e)
{
if (Log.isDebugEnabled())
{
Log.debug("uri=" + _uri);
Log.debug("fields=" + _requestFields);
Log.debug(e);
}
_generator.sendError(e.getStatus(),e.getReason(),null,true);
_parser.reset(true);
_endp.close();
throw e;
}
finally
{
setCurrentConnection(null);
more_in_buffer = _parser.isMoreInBuffer() || _endp.isBufferingInput();
synchronized (this)
{
_handling = false;
if (_destroy)
{
destroy();
return;
}
}
if (_parser.isComplete() && _generator.isComplete() && !_endp.isBufferingOutput())
{
if (!_generator.isPersistent())
{
_parser.reset(true);
more_in_buffer = false;
}
if (more_in_buffer)
{
reset(false);
more_in_buffer = _parser.isMoreInBuffer() || _endp.isBufferingInput();
}
else
reset(true);
no_progress = 0;
}
Continuation continuation = _request.getContinuation();
if (continuation != null && continuation.isPending())
{
break;
}else if (_generator.isCommitted() && !_generator.isComplete() && _endp instanceof SelectChannelEndPoint) // TODO
((SelectChannelEndPoint)_endp).setWritable(false);
}
}
}