- Connector组件的Acceptor监听客户端套接字连接并接收Socket。
- 将连接交给线程池Executor处理，开始执行请求响应任务。
- Processor组件读取消息报文，解析请求行、请求体、请求头，封装成Request对象。
- Mapper组件根据请求行的URL值和请求头的Host值匹配由哪个Host容器、Context容器、Wrapper容器处理请求。
- CoyoteAdaptor组件负责将Connector组件和Engine容器关联起来，把生成的Request对象和响应对象Response传递到Engine容器中，调用 Pipeline。
- Engine容器的管道开始处理，管道中包含若干个Valve、每个Valve负责部分处理逻辑。执行完Valve后会执行基础的 Valve--StandardEngineValve，负责调用Host容器的Pipeline。
- Host容器的管道开始处理，流程类似，最后执行 Context容器的Pipeline。
- Context容器的管道开始处理，流程类似，最后执行 Wrapper容器的Pipeline。
- Wrapper容器的管道开始处理，流程类似，最后执行 Wrapper容器对应的Servlet对象的 处理方法
Connector
<Connector port="8080" protocol="HTTP/1.1"
connectionTimeout="20000"
redirectPort="8443" />
<Connector port="8009" protocol="AJP/1.3" redirectPort="8443" /> Connector用于接收请求并将请求封装成Request和Response来具体处理。最底层使用的是 Socket。Request和Response封装后交给Container（Servlet的容器）处理请求，Container处理后返回给Connector，最后由Socket返回给客户端。
结构
Connector中具体是用 ProtocolHandler处理请求的，代表不同的连接类型。Http11Protocol使用普通Socket连接，Http11NioProtocol使用NioSocket连接。
ProtocolHandler中有三个重要的组件：
- Endpoint：处理底层的Socket网络连接；
- Processor：将Endpoint接收的Socket封装成Request；
- Adapter：将封装后的Request交给Container处理；
Endpoint的抽象类 AbstractEndpoint定义了 Acceptor和 AsyncTimeout两个内部类 和 Handler接口。
- Acceptor：监听请求；
- AsyncTimeout：检查异步Request请求的超时；
- Handler：处理接收的Socket，内部调用 Processor进行处理；
public class Connector extends LifecycleMBeanBase {
public Connector() { this(null); }
public Connector(String protocol) {
// 根据 server.xml 中 Connector 属性 protocol 的值找合适的 className
// 此处返回 org.apache.coyote.http11.Http11NioProtocol
// 赋值给 ProtocolHandler
setProtocol(protocol);
ProtocolHandler p = null;
try {
Class<?> clazz = Class.forName(protocolHandlerClassName);
// 反射生成 Http11NioProtocol 时，在构造函数中 生成了 NioEndpoint。
p = (ProtocolHandler) clazz.getConstructor().newInstance();
} finally {
this.protocolHandler = p;
}
// 设置编码集
if (Globals.STRICT_SERVLET_COMPLIANCE) {
uriCharset = StandardCharsets.ISO_8859_1;
} else {
uriCharset = StandardCharsets.UTF_8;
}
}
// 初始化操作
@Override
protected void initInternal() throws LifecycleException {
super.initInternal();
// 初始化是配置 CoyoteAdapter(Connector 作为参数)
adapter = new CoyoteAdapter(this);
// 协议处理器绑定 适配器
protocolHandler.setAdapter(adapter);
// 执行 协议处理器初始化操作
protocolHandler.init();
}
// 使用此 连接器处理 请求
@Override
protected void startInternal() {
// 验证端口
if (getPort() < 0) { }
// 设置生命周期状态值
setState(LifecycleState.STARTING);
// 调用 协议处理器 start 方法
protocolHandler.start();
}
}
Http11NioProtocol
主要包含 NioEndpoint组件和 Http11NioProcessor组件。启动时由NioEndpoint组件启动端口监听，连接到来被注册到NioChannel队列中，由Poller轮询器负责检测Channel的读写事件，并在创建任务后放入线程池中，线程池进行任务处理。
public class Http11NioProtocol extends AbstractHttp11JsseProtocol<NioChannel> {
// 创建了 NioEndpoint 类
public Http11NioProtocol() {
// 最终调用 AbstractProtocol 类
super(new NioEndpoint());
}
}
// 父类 AbstractProtocol
public abstract class AbstractProtocol implements ProtocolHandler,MBeanRegistration {
@Override
public void init() throws Exception {
// endpointName---"http-nio-8080": http-nio + 8080 组成。
String endpointName = getName();
// 去掉 双引号
endpoint.setName(endpointName.substring(1, endpointName.length()-1));
// domain == catalina
endpoint.setDomain(domain);
// Endpoint的初始化操作
// serverSocketChannel 绑定端口
endpoint.init();
}
@Override
public void start() throws Exception {
// Endpoint 的 start 方法，重点
// 创建 Executor、最大连接、开启 Poller thread
endpoint.start();
// 异步超时 线程，
asyncTimeout = new AsyncTimeout();
Thread timeoutThread = new Thread(asyncTimeout, getNameInternal() + "-AsyncTimeout");
int priority = endpoint.getThreadPriority();
if (priority < Thread.MIN_PRIORITY || priority > Thread.MAX_PRIORITY) {
priority = Thread.NORM_PRIORITY;
}
timeoutThread.setPriority(priority);
timeoutThread.setDaemon(true);
timeoutThread.start();
}
}
// AsyncTimeout 实现 Runnable 接口
protected class AsyncTimeout implements Runnable {
private volatile boolean asyncTimeoutRunning = true;
// 后台线程检查异步请求并在没有活动时触发超时。
@Override
public void run() {
// 死循环，直到接收到 shutdown 命令
while (asyncTimeoutRunning) {
Thread.sleep(1000);
long now = System.currentTimeMillis();
for (Processor processor : waitingProcessors) {
processor.timeoutAsync(now);
}
// 循环，直到 Endpoint pause
while (endpoint.isPaused() && asyncTimeoutRunning) {
Thread.sleep(1000);
}
}
}
}NioEndpoint
NioEndpoint是非阻塞IO的一个抽象，包含了：
- LimitLatch：连接数控制器。
- Acceptor：套接字连接并注册到Channel队列中。
- Poller：轮询检查事件列表。
- SocketProcessor：任务定义器。
- Executor：负责处理套接字。
// AbstractEndpoint
public void init() throws Exception {
if (bindOnInit) {
bind();
bindState = BindState.BOUND_ON_INIT;
}
}
public final void start() throws Exception {
// 判断是否绑定过
if (bindState == BindState.UNBOUND) {
bind();
bindState = BindState.BOUND_ON_START;
}
startInternal();
}
// NioEndpoint
@Override
public void bind() throws Exception {
// 绑定 设置的端口
if (!getUseInheritedChannel()) {
serverSock = ServerSocketChannel.open();
socketProperties.setProperties(serverSock.socket());
InetSocketAddress addr = (getAddress()!=null?new InetSocketAddress(getAddress(),getPort()):new InetSocketAddress(getPort()));
serverSock.socket().bind(addr,getAcceptCount());
} else {
// Retrieve the channel provided by the OS
Channel ic = System.inheritedChannel();
if (ic instanceof ServerSocketChannel) {
serverSock = (ServerSocketChannel) ic;
}
}
// 设置 阻塞模式
serverSock.configureBlocking(true); //mimic APR behavior
// 初始化 连接器、轮询器 默认线程数
if (acceptorThreadCount == 0) {
acceptorThreadCount = 1;
}
if (pollerThreadCount <= 0) {
pollerThreadCount = 1;
}
setStopLatch(new CountDownLatch(pollerThreadCount));
// 是否初始化 ssl
initialiseSsl();
selectorPool.open();
}
// 开启 NIO endpoint, 创建 acceptor, poller 线程.
@Override
public void startInternal() throws Exception {
// 设置 running 状态
if (!running) {
running = true;
paused = false;
// 默认 DEFAULT_SIZE：128 500
processorCache = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
socketProperties.getProcessorCache());
eventCache = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
socketProperties.getEventCache());
nioChannels = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
socketProperties.getBufferPool());
if ( getExecutor() == null ) {
createExecutor();
}
// 初始化 连接数控制器，默认最大连接数 10000
initializeConnectionLatch();
// 开启 poller 线程， 默认 2
// 检测到 事件后，交给 processor 处理
pollers = new Poller[getPollerThreadCount()];
for (int i=0; i<pollers.length; i++) {
pollers[i] = new Poller();
Thread pollerThread = new Thread(pollers[i],
getName() + "-ClientPoller-"+i);
pollerThread.setPriority(threadPriority);
pollerThread.setDaemon(true);
pollerThread.start();
}
// 开启 Acceptor 线程
startAcceptorThreads();
}
}
// AbstractEndpoint
protected final void startAcceptorThreads() {
int count = getAcceptorThreadCount();
acceptors = new Acceptor[count];
// 开启 Acceptor 线程
for (int i = 0; i < count; i++) {
// NioEndpoint 中实现
acceptors[i] = createAcceptor();
String threadName = getName() + "-Acceptor-" + i;
acceptors[i].setThreadName(threadName);
Thread t = new Thread(acceptors[i], threadName);
t.setPriority(getAcceptorThreadPriority());
t.setDaemon(getDaemon());
t.start();
}
}连接数控制器-------LimitLatch
处理流程图：
NIO模式下，Tomcat默认把阀门大小设置为 10000，可在 server.xml Connector节点下配置 maxConnections 属性修改。在连接数到达最大值后，仍可以接收客户端连接，直到操作系统接收队列被塞满。默认100，可在 Connector节点下 配置 acceptCount 属性修改。
SocketChannel接收器--------Acceptor
Acceptor主要监听是否有客户端发来的连接并接收该连接，accept操作是阻塞的。此时返回 SocketChannel对象。Acceptor接收 SocketChannel 对象后要把它设置成非阻塞（后面对客户端连接才去非阻塞模式处理），接着设置套接字属性，封装成非阻塞通道对象。（NioChannel--HTTP、SecureNioChannel--HTTPS），最后将非阻塞通道对象注册到通道队列由 Poller 负责检测事件。
// NioEndpoint
protected class Acceptor extends AbstractEndpoint.Acceptor {
@Override
public void run() {
int errorDelay = 0;
// 死循环，知道收到 shutdown 命令
while (running) {
// Loop if endpoint is paused
while (paused && running) {
state = AcceptorState.PAUSED;
Thread.sleep(50);
}
if (!running) {
break;
}
state = AcceptorState.RUNNING;
try {
// 超过最大 连接，等待状态
countUpOrAwaitConnection();
// 接收从server来的下一个socket连接
SocketChannel socket = serverSock.accept();
// 正确接收 socket，重置 errorDelay
errorDelay = 0;
// Configure the socket
if (running && !paused) {
// 把 socket 交给合适的 处理器处理
if (!setSocketOptions(socket)) {
closeSocket(socket);
}
} else {
closeSocket(socket);
}
}
}
state = AcceptorState.ENDED;
}
}
protected boolean setSocketOptions(SocketChannel socket) {
// 处理 socket
try {
// 设置 非阻塞模式
socket.configureBlocking(false);
Socket sock = socket.socket();
socketProperties.setProperties(sock);
NioChannel channel = nioChannels.pop();
if (channel == null) {
SocketBufferHandler bufhandler = new SocketBufferHandler(
socketProperties.getAppReadBufSize(),
socketProperties.getAppWriteBufSize(),
socketProperties.getDirectBuffer());
// 判断是否开启 SSL 类型，生成不同类型的 Channel
if (isSSLEnabled()) {
channel = new SecureNioChannel(socket, bufhandler, selectorPool, this);
} else {
channel = new NioChannel(socket, bufhandler);
}
} else {
channel.setIOChannel(socket);
channel.reset();
}
// 获取 Poller，注册 成 Event 事件。
getPoller0().register(channel);
} catch (Throwable t) {
// 出错了，就返回，进行 关闭 socket 处理
return false;
}
return true;
}轮询器----Poller
需要同时对很多连接进行管理，通过不断遍历事件列表，对对应连接的相应事件作出处理。Poller内部依赖 JDK的Selector对象进行轮询，Selector会选择出待处理的事件，每轮询一次就选出若干需要处理的NioChannel，在NIO模式下，每次读取的数据时不确定的，每次读取的数据可能有请求头和请求行，每次只能尝试去解析报文，如果解析不成功则等待下次轮询读取更多数据后再次尝试，如果解析成功则做一些逻辑处理后对客户端响应，这些处理工作在任务定义器中定义。
// 在 NioEndpoint startInternal方法中
pollers = new Poller[getPollerThreadCount()];
for (int i=0; i<pollers.length; i++) {
pollers[i] = new Poller();
Thread pollerThread = new Thread(pollers[i], getName() + "-ClientPoller-"+i);
pollerThread.setPriority(threadPriority);
pollerThread.setDaemon(true);
pollerThread.start();
}
// NioEndpoint 类中定义
public class Poller implements Runnable {
private final SynchronizedQueue<PollerEvent> events =
new SynchronizedQueue<>();
private volatile boolean close = false;
private Selector selector;
@Override
public void run() {
// 死循环，直到调用 destory 法
while (true) {
boolean hasEvents = false;
try {
if (!close) {
// 在 Acceptor 收到请求封装成 Socket 注册到 event 中
// 在轮询时从Event中取，进行处理
hasEvents = events();
if (wakeupCounter.getAndSet(-1) > 0) {
//if we are here, means we have other stuff to do
//do a non blocking select
keyCount = selector.selectNow();
} else {
keyCount = selector.select(selectorTimeout);
}
wakeupCounter.set(0);
}
if (close) {
events();
timeout(0, false);
try {
selector.close();
} catch (IOException ioe) {
log.error(sm.getString("endpoint.nio.selectorCloseFail"), ioe);
}
break;
}
} catch (Throwable x) {
continue;
}
//either we timed out or we woke up, process events first
if ( keyCount == 0 ) hasEvents = (hasEvents | events());
Iterator<SelectionKey> iterator =
keyCount > 0 ? selector.selectedKeys().iterator() : null;
// Walk through the collection of ready keys and dispatch
// any active event.
while (iterator != null && iterator.hasNext()) {
SelectionKey sk = iterator.next();
NioSocketWrapper attachment = (NioSocketWrapper)sk.attachment();
// 另一个线程调用了 cancelledKey 方法，attachment 可能为null
// 移除次事件，否则进行处理事件
if (attachment == null) {
iterator.remove();
} else {
iterator.remove();
processKey(sk, attachment);
}
}
// 处理超时情况
timeout(keyCount,hasEvents);
}
getStopLatch().countDown();
}
protected void processKey(SelectionKey sk, NioSocketWrapper attachment) {
try {
if ( close ) {
cancelledKey(sk);
} else if ( sk.isValid() && attachment != null ) {
if (sk.isReadable() || sk.isWritable() ) {
if ( attachment.getSendfileData() != null ) {
processSendfile(sk,attachment, false);
} else {
unreg(sk, attachment, sk.readyOps());
boolean closeSocket = false;
// Read goes before write
if (sk.isReadable()) {
// 在父类中定义
if (!processSocket(attachment, SocketEvent.OPEN_READ, true)) {
closeSocket = true;
}
}
if (!closeSocket && sk.isWritable()) {
if (!processSocket(attachment, SocketEvent.OPEN_WRITE, true)) {
closeSocket = true;
}
}
if (closeSocket) {
cancelledKey(sk);
}
}
}
} else {
//invalid key
cancelledKey(sk);
}
} catch ( CancelledKeyException ckx ) {
cancelledKey(sk);
}
}
}
// AbstractEndpoint
public boolean processSocket(SocketWrapperBase<S> socketWrapper,
SocketEvent event, boolean dispatch) {
try {
if (socketWrapper == null) {
return false;
}
// 从 栈中取一个
SocketProcessorBase<S> sc = processorCache.pop();
if (sc == null) {
// 没有就新建一个
sc = createSocketProcessor(socketWrapper, event);
} else {
sc.reset(socketWrapper, event);
}
// 判断是否有 Executor，最终都是调用 Processor 的 run方法。
Executor executor = getExecutor();
// 见SocketProcessor
if (dispatch && executor != null) {
executor.execute(sc);
} else {
sc.run();
}
} catch (RejectedExecutionException ree) {
return false;
}
return true;
}任务定义器---SocketProcessor
// 在上面的操作中，执行 run 方法时，
// SocketProcessorBase
@Override
public final void run() {
synchronized (socketWrapper) {
if (socketWrapper.isClosed()) {
return;
}
doRun();
}
}
// 在 NioEndpoint 类中实现
@Override
protected void doRun() {
NioChannel socket = socketWrapper.getSocket();
SelectionKey key = socket.getIOChannel().keyFor(socket.getPoller().getSelector());
int handshake = -1;
if (handshake == 0) {
SocketState state = SocketState.OPEN;
// 处理请求
if (event == null) {
// 调用 Handler 转交给 Processor 去处理 process 方法，
state = getHandler().process(socketWrapper, SocketEvent.OPEN_READ);
} else {
state = getHandler().process(socketWrapper, event);
}
if (state == SocketState.CLOSED) {
close(socket, key);
}
}
socketWrapper = null;
event = null;
//return to cache
if (running && !paused) {
processorCache.push(this);
}
}
// AbstractProtocol
protected static class ConnectionHandler<S> implements AbstractEndpoint.Handler<S> {
@Override
public SocketState process(SocketWrapperBase<S> wrapper, SocketEvent status) {
if (wrapper == null) {
return SocketState.CLOSED;
}
S socket = wrapper.getSocket();
// 根据Socket获取具体协议的处理器
Processor processor = connections.get(socket);
// 如果process==null，尝试其它协议、新建等
// SSL 支持
processor.setSslSupport(
wrapper.getSslSupport(getProtocol().getClientCertProvider()));
// process 和 connection 关联
connections.put(socket, processor);
SocketState state = SocketState.CLOSED;
do {
// 处理
state = processor.process(wrapper, status);
} while ( state == SocketState.UPGRADING);
// Make sure socket/processor is removed from the list of current
connections.remove(socket);
release(processor);
return SocketState.CLOSED;
}
}
// AbstractProcessorLight(公共父类)
@Override
public SocketState process(SocketWrapperBase<?> socketWrapper, SocketEvent status)
throws IOException {
SocketState state = SocketState.CLOSED;
Iterator<DispatchType> dispatches = null;
do {
// 根据 SocketEvent 所处的 状态执行不同操作。
if (dispatches != null) {
DispatchType nextDispatch = dispatches.next();
state = dispatch(nextDispatch.getSocketStatus());
} else if (status == SocketEvent.DISCONNECT) {
// Do nothing here, just wait for it to get recycled
} else if (isAsync() || isUpgrade() || state == SocketState.ASYNC_END) {
state = dispatch(status);
if (state == SocketState.OPEN) {
state = service(socketWrapper);
}
} else if (status == SocketEvent.OPEN_WRITE) {
state = SocketState.LONG;
} else if (status == SocketEvent.OPEN_READ){
state = service(socketWrapper);
} else {
state = SocketState.CLOSED;
}
if (state != SocketState.CLOSED && isAsync()) {
state = asyncPostProcess();
}
if (dispatches == null || !dispatches.hasNext()) {
dispatches = getIteratorAndClearDispatches();
}
} while (state == SocketState.ASYNC_END ||
dispatches != null && state != SocketState.CLOSED);
return state;
}
// 调用具体协议的service方法处理请求
@Override
public SocketState service(SocketWrapperBase<?> socketWrapper) {
// 判断状态
while (!getErrorState().isError() && keepAlive && !isAsync()
&& upgradeToken == null &&
sendfileState == SendfileState.DONE && !endpoint.isPaused()) {
// 解析request请求头
try {
if (!inputBuffer.parseRequestLine(keptAlive)) {
if (inputBuffer.getParsingRequestLinePhase() == -1) {
return SocketState.UPGRADING;
} else if (handleIncompleteRequestLineRead()) {
break;
}
}
if (endpoint.isPaused()) {
response.setStatus(503);
setErrorState(ErrorState.CLOSE_CLEAN, null);
} else {
keptAlive = true;
request.getMimeHeaders().setLimit(endpoint.getMaxHeaderCount());
if (!inputBuffer.parseHeaders()) {
openSocket = true;
readComplete = false;
break;
}
if (!disableUploadTimeout) {
socketWrapper.setReadTimeout(connectionUploadTimeout);
}
}
} catch (IOException e) {
setErrorState(ErrorState.CLOSE_CONNECTION_NOW, e); break;
} catch (Throwable t) {
// 400 - Bad Request
response.setStatus(400);
setErrorState(ErrorState.CLOSE_CLEAN, t);
// 日志调用处
getAdapter().log(request, response, 0);
}
// Has an upgrade been requested?
Enumeration<String> connectionValues = request.getMimeHeaders().values("Connection");
boolean foundUpgrade = false;
while (connectionValues.hasMoreElements() && !foundUpgrade) {
foundUpgrade = connectionValues.nextElement().toLowerCase(
Locale.ENGLISH).contains("upgrade");
}
if (foundUpgrade) {
// Check the protocol
String requestedProtocol = request.getHeader("Upgrade");
UpgradeProtocol upgradeProtocol = httpUpgradeProtocols.get(requestedProtocol);
if (upgradeProtocol != null) {
if (upgradeProtocol.accept(request)) {
response.setStatus(HttpServletResponse.SC_SWITCHING_PROTOCOLS);
response.setHeader("Connection", "Upgrade");
response.setHeader("Upgrade", requestedProtocol);
action(ActionCode.CLOSE, null);
getAdapter().log(request, response, 0);
InternalHttpUpgradeHandler upgradeHandler =
upgradeProtocol.getInternalUpgradeHandler(
getAdapter(), cloneRequest(request));
UpgradeToken upgradeToken = new UpgradeToken(upgradeHandler, null, null);
action(ActionCode.UPGRADE, upgradeToken);
return SocketState.UPGRADING;
}
}
}
if (!getErrorState().isError()) {
rp.setStage(org.apache.coyote.Constants.STAGE_PREPARE);
try {
prepareRequest();
} catch (Throwable t) {
// 500 - Internal Server Error
response.setStatus(500);
setErrorState(ErrorState.CLOSE_CLEAN, t);
getAdapter().log(request, response, 0);
}
}
if (maxKeepAliveRequests == 1) {
keepAlive = false;
} else if (maxKeepAliveRequests > 0 &&
socketWrapper.decrementKeepAlive() <= 0) {
keepAlive = false;
}
// 通过 CoyotAdapte 处理 request
if (!getErrorState().isError()) {
try {
rp.setStage(org.apache.coyote.Constants.STAGE_SERVICE);
// 处理 request，见 CoyoteAdapter 解析
getAdapter().service(request, response);
if(keepAlive && !getErrorState().isError() && !isAsync() &&
statusDropsConnection(response.getStatus())) {
setErrorState(ErrorState.CLOSE_CLEAN, null);
}
} catch (InterruptedIOException e) {
setErrorState(ErrorState.CLOSE_CONNECTION_NOW, e);
} catch (HeadersTooLargeException e) {
if (response.isCommitted()) {
setErrorState(ErrorState.CLOSE_NOW, e);
} else {
response.reset();
response.setStatus(500);
setErrorState(ErrorState.CLOSE_CLEAN, e);
response.setHeader("Connection", "close");
}
} catch (Throwable t) {
// 500 - Internal Server Error
response.setStatus(500);
setErrorState(ErrorState.CLOSE_CLEAN, t);
getAdapter().log(request, response, 0);
}
}
// Finish the handling of the request
rp.setStage(org.apache.coyote.Constants.STAGE_ENDINPUT);
if (!isAsync()) {
endRequest();
}
rp.setStage(org.apache.coyote.Constants.STAGE_ENDOUTPUT);
// If there was an error, make sure the request is counted as
// and error, and update the statistics counter
if (getErrorState().isError()) {
response.setStatus(500);
}
if (!isAsync() || getErrorState().isError()) {
request.updateCounters();
if (getErrorState().isIoAllowed()) {
inputBuffer.nextRequest();
outputBuffer.nextRequest();
}
}
if (!disableUploadTimeout) {
int soTimeout = endpoint.getConnectionTimeout();
if(soTimeout > 0) {
socketWrapper.setReadTimeout(soTimeout);
} else {
socketWrapper.setReadTimeout(0);
}
}
rp.setStage(org.apache.coyote.Constants.STAGE_KEEPALIVE);
sendfileState = processSendfile(socketWrapper);
}
rp.setStage(org.apache.coyote.Constants.STAGE_ENDED);
}CoyoteAdapter
@Override
public void service(org.apache.coyote.Request req, org.apache.coyote.Response res) {
Request request = (Request) req.getNote(ADAPTER_NOTES);
Response response = (Response) res.getNote(ADAPTER_NOTES);
// request == null，新建并关联
if (request == null) {
// Create objects
request = connector.createRequest();
request.setCoyoteRequest(req);
response = connector.createResponse();
response.setCoyoteResponse(res);
// Link objects
request.setResponse(response);
response.setRequest(request);
// Set as notes
req.setNote(ADAPTER_NOTES, request);
res.setNote(ADAPTER_NOTES, response);
// Set query string encoding
req.getParameters().setQueryStringCharset(connector.getURICharset());
}
// 设置请求头，告知网站是用何种语言或框架编写的
// 默认false，Servlet/4.0 JSP/2.3xxxxxxxxxxxxxx
if (connector.getXpoweredBy()) {
response.addHeader("X-Powered-By", POWERED_BY);
}
boolean async = false;
boolean postParseSuccess = false;
req.getRequestProcessor().setWorkerThreadName(THREAD_NAME.get());
try {
// 请求映射、解析参数等操作。
postParseSuccess = postParseRequest(req, request, res, response);
if (postParseSuccess) {
//check valves if we support async
request.setAsyncSupported(
connector.getService()
.getContainer()
.getPipeline()
.isAsyncSupported());
// 由 Pipeline 处理流程，见Pipeline篇
connector.getService()
.getContainer()
.getPipeline()
.getFirst()
.invoke(request, response);
}
// 异步处理
if (request.isAsync()) {
// 省略
} else {
request.finishRequest();
response.finishResponse();
}
} finally {
// 处理访问日志，见日志篇
if (!async && postParseSuccess) {
Context context = request.getContext();
if (context != null) {
context.logAccess(request, response,
System.currentTimeMillis() - req.getStartTime(), false);
}
}
req.getRequestProcessor().setWorkerThreadName(null);
// 回收 request and response
if (!async) {
request.recycle();
response.recycle();
}
}
}