tomcat請求流程源碼解進(jìn)階篇
更新時間：2023年09月01日 14:10:59 作者：湯卜
這篇文章主要為大家介紹了tomcat請求流程源碼解進(jìn)階,有需要的朋友可以借鑒參考下,希望能夠有所幫助,祝大家多多進(jìn)步,早日升職加薪
Connector的初始化
catalina解析server.xml是通過degister來實(shí)現(xiàn)的，degister解析到<Connector標(biāo)簽后做的事情如下代碼所見
ConnectorCreateRule
@Override
public void begin(String namespace, String name, Attributes attributes)
throws Exception {
Service svc = (Service)digester.peek();
Executor ex = null;
if ( attributes.getValue("executor")!=null ) {
ex = svc.getExecutor(attributes.getValue("executor"));
}
Connector con = new Connector(attributes.getValue("protocol"));
if (ex != null) {
setExecutor(con, ex);
}
String sslImplementationName = attributes.getValue("sslImplementationName");
if (sslImplementationName != null) {
setSSLImplementationName(con, sslImplementationName);
}
digester.push(con);
}connector根據(jù)標(biāo)簽屬性，拿到對應(yīng)的protocol協(xié)議，拿到配在service標(biāo)簽內(nèi)部的線程池，protocol的名稱轉(zhuǎn)化成Connector中ProtocolHandler類型的成員變量, 后續(xù)將以Http11NioProtocol來做講解
public Connector(String protocol) {
setProtocol(protocol);
// Instantiate protocol handler
ProtocolHandler p = null;
try {
Class<?> clazz = Class.forName(protocolHandlerClassName);
// 反射調(diào)用ProtocolHandler的構(gòu)造方法的時候會做后續(xù)的初始化
p = (ProtocolHandler) clazz.getConstructor().newInstance();
} catch (Exception e) {
log.error(sm.getString("coyoteConnector.protocolHandlerInstantiationFailed"), e);
} finally {
this.protocolHandler = p;
}ProtocolHandler的構(gòu)造
ProtocolHandler有其抽象方法，Http11NioProtocol構(gòu)造方法中的tcp實(shí)現(xiàn)由NioEndpoint來做，因此Connector構(gòu)造起來的時候，對應(yīng)的ProtocolHanlder、endpoint的關(guān)聯(lián)關(guān)系已經(jīng)關(guān)聯(lián)好
public AbstractProtocol(AbstractEndpoint<S, ?> endpoint) {
this.endpoint = endpoint;
ConnectionHandler<S> cHandler = new ConnectionHandler<>(this);
setHandler(cHandler);
getEndpoint().setHandler(cHandler);
setSoLinger(Constants.DEFAULT_CONNECTION_LINGER);
setTcpNoDelay(Constants.DEFAULT_TCP_NO_DELAY);
}構(gòu)造后的init方法
在解析server.xml的基本層次結(jié)構(gòu)，成員變量填充完整后，需要調(diào)用生命周期的init方法
org/apache/catalina/startup/Catalina.load
getServer().init(); -----> connector.init(); --------------> protocolHandler.init();
----------> endpoint.init(); ------------->
看一下NioEndpoint的init方法
protected void initServerSocket() throws Exception {
if (getUseInheritedChannel()) {
// Retrieve the channel provided by the OS
Channel ic = System.inheritedChannel();
if (ic instanceof ServerSocketChannel) {
serverSock = (ServerSocketChannel) ic;
}
if (serverSock == null) {
throw new IllegalArgumentException(sm.getString("endpoint.init.bind.inherited"));
}
} else {
// 綁定服務(wù)端的傳輸層端口
serverSock = ServerSocketChannel.open();
socketProperties.setProperties(serverSock.socket());
InetSocketAddress addr = new InetSocketAddress(getAddress(), getPortWithOffset());
serverSock.socket().bind(addr,getAcceptCount());
}
serverSock.configureBlocking(true); //mimic APR behavior
}建立Nio的Acceptor線程和Selector事件線程
org.apache.tomcat.util.net.NioEndpoint#startInternal
public void startInternal() throws Exception {
if (!running) {
running = true;
paused = false;
if (socketProperties.getProcessorCache() != 0) {
processorCache = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
socketProperties.getProcessorCache());
}
if (socketProperties.getEventCache() != 0) {
eventCache = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
socketProperties.getEventCache());
}
if (socketProperties.getBufferPool() != 0) {
nioChannels = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
socketProperties.getBufferPool());
}
// Create worker collection
if (getExecutor() == null) {
// 創(chuàng)建Tomcat默認(rèn)線程池，未手動配置 線程數(shù)10 - 200
createExecutor();
}
// 這個是tomcat的連接數(shù)限制器
initializeConnectionLatch();
// Start poller thread
poller = new Poller();
Thread pollerThread = new Thread(poller, getName() + "-Poller");
pollerThread.setPriority(threadPriority);
pollerThread.setDaemon(true);
pollerThread.start();
startAcceptorThread();
}
}我們來看一下Poller的實(shí)現(xiàn)和Acctptor的實(shí)現(xiàn)
Poller的實(shí)現(xiàn)
public class Poller implements Runnable {
private Selector selector;
// PollerEvent private NioSocketWrapper socketWrapper; private int interestOps;
// 向多路復(fù)用器注冊socket和需要處理的socket時間
private final SynchronizedQueue<PollerEvent> events =
new SynchronizedQueue<>();
.........
public Poller() throws IOException {
this.selector = Selector.open();
}
@Override
public void run() {
// Loop until destroy() is called
while (true) {
boolean hasEvents = false;
try {
if (!close) {
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 {
// 默認(rèn)阻塞1秒鐘，監(jiān)聽需要交給線程池的處理任務(wù)
keyCount = selector.select(selectorTimeout);
}
wakeupCounter.set(0);
}
...
} catch (Throwable x) {
ExceptionUtils.handleThrowable(x);
log.error(sm.getString("endpoint.nio.selectorLoopError"), x);
continue;
}
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();
iterator.remove();
NioSocketWrapper socketWrapper = (NioSocketWrapper) sk.attachment();
// Attachment may be null if another thread has called
// cancelledKey()
if (socketWrapper != null) {
// 主角， 任務(wù)處理都在里面
processKey(sk, socketWrapper);
}
}
// Process timeouts
timeout(keyCount,hasEvents);
}
.............
}Acctptor的實(shí)現(xiàn)
public class Acceptor<U> implements Runnable {
@Override
public void run() {
int errorDelay = 0;
long pauseStart = 0;
try {
// Loop until we receive a shutdown command
while (!stopCalled) {
............
if (stopCalled) {
break;
}
state = AcceptorState.RUNNING;
try {
//if we have reached max connections, wait
endpoint.countUpOrAwaitConnection();
// Endpoint might have been paused while waiting for latch
// If that is the case, don't accept new connections
if (endpoint.isPaused()) {
continue;
}
U socket = null;
try {
// 等待新連接
socket = endpoint.serverSocketAccept();
} catch (Exception ioe) {
// We didn't get a socket
endpoint.countDownConnection();
if (endpoint.isRunning()) {
// Introduce delay if necessary
errorDelay = handleExceptionWithDelay(errorDelay);
// re-throw
throw ioe;
} else {
break;
}
}
// Successful accept, reset the error delay
errorDelay = 0;
// Configure the socket
if (!stopCalled && !endpoint.isPaused()) {
// 由endpoint來處理新連接、把新連接存在map里、向poller注冊PollerEndpoint
// 以后讀寫事件就由Poller交給線程池來管理
if (!endpoint.setSocketOptions(socket)) {
endpoint.closeSocket(socket);
}
} else {
endpoint.destroySocket(socket);
}
}
........
} finally {
stopLatch.countDown();
}
state = AcceptorState.ENDED;
}
}當(dāng)新連接接入時，會把新連接注冊到至底層為Selector的多路復(fù)用器上，Tomcat的Connector擁有了接受新連接和處理socket事件的能力
項目實(shí)戰(zhàn)
依舊使用mytomcat.war， 里面有一個servlet FirstServlet,跟隨tomcat一起啟動，容器啟動，項目的部署暫且不討論
接下來我們看一下一個簡單的Servlet如何在tomcat中來流轉(zhuǎn)
tomcat啟動時， Acceptor將阻塞到 socket = endpoint.serverSocketAccept();這一行
在瀏覽器輸入http://localhost:8080/mytomcat/servlet1， Acceptor解除阻塞并且獲取到客戶端socket
來看一下endpoint.setSocketOptions(socket)做了啥
@Override
protected boolean setSocketOptions(SocketChannel socket) {
.........
NioSocketWrapper newWrapper = new NioSocketWrapper(channel, this);
channel.reset(socket, newWrapper);
connections.put(socket, newWrapper);
socketWrapper = newWrapper;
// Set socket properties
// Disable blocking, polling will be used
socket.configureBlocking(false);
socketProperties.setProperties(socket.socket());
// 注冊新連接
poller.register(socketWrapper);
return true;
...再看一下Poller的代碼 監(jiān)聽了新連接的OP_READ事件
public void register(final NioSocketWrapper socketWrapper) {
socketWrapper.interestOps(SelectionKey.OP_READ);//this is what OP_REGISTER turns into.
PollerEvent pollerEvent = createPollerEvent(socketWrapper, OP_REGISTER);
addEvent(pollerEvent);
}這樣，http://localhost:8080/mytomcat/servlet1的請求就會交給Poller處理，詳細(xì)代碼見Poller的run函數(shù)
public void run() {
// Loop until destroy() is called
while (true) {
boolean hasEvents = false;
try {
if (!close) {
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 {
// 默認(rèn)阻塞1秒鐘，監(jiān)聽需要交給線程池的處理任務(wù)
keyCount = selector.select(selectorTimeout);
}
wakeupCounter.set(0);
}
...
} catch (Throwable x) {
ExceptionUtils.handleThrowable(x);
log.error(sm.getString("endpoint.nio.selectorLoopError"), x);
continue;
}
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();
iterator.remove();
NioSocketWrapper socketWrapper = (NioSocketWrapper) sk.attachment();
// Attachment may be null if another thread has called
// cancelledKey()
if (socketWrapper != null) {
// 主角， 任務(wù)處理都在里面
processKey(sk, socketWrapper);
}
}
// Process timeouts
timeout(keyCount,hasEvents);
}
.............
}processKey的時候向線程池提交一個SocketProcessor任務(wù)
多線程任務(wù)的執(zhí)行
經(jīng)過一系列變換，connecotr對應(yīng)的Handler為Http11Nio Protocol，將協(xié)議部分的處理交由Http11Processor
CoyoteAdapter
tomcat并非直接把請求封裝為HttpServletRequest對象和HttpServletResponse對象，本身connector支持多種協(xié)議，不只使用http協(xié)議。所以tomcat存在比較底層的org.apache.coyote.Request， 也存在繼承HttpServletRequest的org.apache.catalina.connector.Request，CoyoteAdapter負(fù)責(zé)做二者的轉(zhuǎn)化并且把轉(zhuǎn)化后的HttpServletRequest對象和HttpServletResponse對象交給tomcat容器的Pipeline。
來看一下CoyoteAdapter的service方法
public void service(org.apache.coyote.Request req, org.apache.coyote.Response res) throws Exception {
Request request = (Request) req.getNote(ADAPTER_NOTES);
Response response = (Response) res.getNote(ADAPTER_NOTES);
if (request == null) {
// Create objects
request = connector.createRequest();
request.setCoyoteRequest(req);
response = connector.createResponse();
response.setCoyoteResponse(res);
// 做兩種類型request的轉(zhuǎn)換
request.setResponse(response);
response.setRequest(request);
}
try {
// Parse and set Catalina and configuration specific
// 下面有講解這個方法
postParseSuccess = postParseRequest(req, request, res, response);
if (postParseSuccess) {
// check valves if we support async
request.setAsyncSupported(connector.getService().getContainer().getPipeline().isAsyncSupported());
// Calling the container
//把HttpServletRequest 和HttpServletRequest對象交給tomcat的職責(zé)鏈Pipeline。
connector.getService().getContainer().getPipeline().getFirst().invoke(request, response);
}
........
}我們來看一下postParseRequest(req, resp)方法
protected boolean postParseRequest(org.apache.coyote.Request req, Request request, org.apache.coyote.Response res,
Response response) throws IOException, ServletException {
// 解析出是否要Https
if (req.scheme().isNull()) {
// Use connector scheme and secure configuration, (defaults to
// "http" and false respectively)
req.scheme().setString(connector.getScheme());
request.setSecure(connector.getSecure());
} else {
// Use processor specified scheme to determine secure state
request.setSecure(req.scheme().equals("https"));
}
// 代理相關(guān)
String proxyName = connector.getProxyName();
int proxyPort = connector.getProxyPort();
if (proxyPort != 0) {
req.setServerPort(proxyPort);
} else if (req.getServerPort() == -1) {
// Not explicitly set. Use default ports based on the scheme
if (req.scheme().equals("https")) {
req.setServerPort(443);
} else {
req.setServerPort(80);
}
}
if (proxyName != null) {
req.serverName().setString(proxyName);
}
// 預(yù)檢方法請求
// Check for ping OPTIONS * request
if (undecodedURI.equals("*")) {
if (req.method().equalsIgnoreCase("OPTIONS")) {
StringBuilder allow = new StringBuilder();
allow.append("GET, HEAD, POST, PUT, DELETE, OPTIONS");
// Trace if allowed
if (connector.getAllowTrace()) {
allow.append(", TRACE");
}
res.setHeader("Allow", allow.toString());
// Access log entry as processing won't reach AccessLogValve
connector.getService().getContainer().logAccess(request, response, 0, true);
return false;
} else {
response.sendError(400, sm.getString("coyoteAdapter.invalidURI"));
}
}
........
while (mapRequired) {
// This will map the the latest version by default
// tomcat可以部署多個應(yīng)用，找到具體在某個Context、Host、填充到request對象中。
connector.getService().getMapper().map(serverName, decodedURI, version, request.getMappingData());
}
.......探索一下tomcat的職責(zé)鏈
正式進(jìn)入Tomcat的職責(zé)鏈中，下面我們來看一下pipeline中有什么
因為已有環(huán)境，本文直接給出默認(rèn)的鏈裝結(jié)構(gòu)
StandardEngineValve----> AccessLogValve----> ErrorReportValve---- > StandardHostValve ----> StandardContextValve -----> StandardWrapperValve---> ApplicationFilterChain ---后續(xù)執(zhí)行指定的Servlet
排除容器本身的節(jié)點(diǎn)StandardEngineValve， StandardHostValve，StandardContextValve三個節(jié)點(diǎn)。 AccessLogValve，ErrorReportValve， StandardWrapperValve值得我們關(guān)注
AccessLogValve:使用來記錄訪問請求的基本信息，記錄到access.log中等
ErrorReportValve:來處理后面的錯誤，跳到失敗頁面等
StandardWrapperValve: 如下詳細(xì)解說
@Override
public void invoke(Request request, Response response) throws IOException, ServletException {
...........
// 獲取對應(yīng)servlet對應(yīng)的Wrapper， servlet可能還未加載
StandardWrapper wrapper = (StandardWrapper) getContainer();
Servlet servlet = null;
Context context = (Context) wrapper.getParent();
........
try {
if (!unavailable) {
// 獲取真正的servlet， 如果未加載初始化，在加載初始化后返回
servlet = wrapper.allocate();
}
} catch (UnavailableException e) {
container.getLogger().error(sm.getString("standardWrapper.allocateException", wrapper.getName()), e);
checkWrapperAvailable(response, wrapper);
}
.................
// ApplicationFilterChain本身是servlet規(guī)范中的過濾器， 持有servelt對象，使用職責(zé)鏈調(diào)用完成后，再調(diào)用servlet， 至此，tomcat的請求流程到此，后續(xù)交給上層應(yīng)用程序來處理請求
ApplicationFilterChain filterChain = ApplicationFilterFactory.createFilterChain(request, wrapper, servlet);
.........
filterChain.doFilter(request.getRequest(), response.getResponse());至此，tomcat講請求處理完后遞交給上層應(yīng)用程序來處理，并返回結(jié)果，依次寫回
本文到此結(jié)束，tomcat的源碼還有很多，如容器之間的關(guān)系，多類的加載安全性，動態(tài)部署等，有興趣的朋友可以繼續(xù)研究，更多關(guān)于tomcat請求流程的資料請關(guān)注腳本之家其它相關(guān)文章！
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