（tornado源码分析_004）HTTP服务器处理解析出来的http数据

#常见的torando启动方式
application = tornado.web.Application(Handlers)
application.listen(8888) 

class Application(ReversibleRouter):
    def listen(self):
        #启动时创建HTTPServer
        from tornado.httpserver import HTTPServer
        server = HTTPServer(self, **kwargs)
        server.listen(port, address)
        return server

class HTTPServer(TCPServer,Configurable,httputil.HTTPServerConnectionDelegate):   
    def __init__(self, application):
        #将application包装成_CallableAdapter，因为application负责处理完整的request，
        self.delegate = _CallableAdapter(application)

class HTTP1Connection(httputil.HTTPConnection):
    def read_response(self, delegate):
        if self.params.decompress:
            delegate = _GzipMessageDelegate(delegate, self.params.chunk_size)
        return self._read_message(delegate)

    def _read_message(self, delegate):
        #调用上层即HTTPServer处理解析出来的http消息头部，该处理也是异步的
        delegate.headers_received(start_line, headers)
    
    def _read_body(self, code, headers, delegate):
        #body可能较大，时分片到达的
        delegate.data_received(chunk)

class _CallableAdapter(httputil.HTTPMessageDelegate):
    def __init__(self, request_callback, request_conn):
        self.connection = request_conn
        self.request_callback = request_callback
        self.request = None
        self.delegate = None
        self._chunks = []

    def headers_received(self, start_line, headers):
        #当代用该函数时，说明是一个新的请求，创建request
        self.request = httputil.HTTPServerRequest(
            connection=self.connection, start_line=start_line,
            headers=headers)

    def data_received(self, chunk):
        #body是分片到达的，保存，以便最后组装
        self._chunks.append(chunk)

    def finish(self):
        #组装body
        self.request.body = b‘‘.join(self._chunks)
        self.request._parse_body()
        
        #调用application（tornado的web框架）处理request
        self.request_callback(self.request)

    def on_connection_close(self):
        self._chunks = None