前言
tomcat最全uml类图
tomcat请求处理过程：
connector对象创建的时候，会创建http11nioprotocol的protocolhandler，在connector的startinteral方法中，会启动abstractprotocol，abstractprotocol启动nioendpoint进行监听客户端的请求，endpoint接受到客户端的请求之后，会交给container去处理请求。请求从engine开始经过的所有容器都含有责任链模式，每经过一个容器都会调用该容器的责任链对请求进行处理。
一、endpoint
默认的endpoint实现是nioendpoint，nioendpoint有四个内部类，分别是poller、acceptor、pollerevent、socketprocessor、niosocketwrapper。
（1）acceptor负责监听用户的请求，监听到用户请求之后，调用getpoller0().register(channel);先将当前请求封装成pollerevent，new pollerevent(socket, ka, op_register); 将当前请求，封装成注册事件，并添加到pollerevent队列中，然后将pollerevent注册到poller的selector对象上面。
（2）poller线程会一直遍历可以处理的事件（netty的selestor），当找到需要处理的事件之后，调用processkey(sk, socketwrapper);对，执行要处理的pollerevent的run方法，对请求进行处理。
（3）pollerevent继承自runnable接口，在其run方法里面,如果是pollerevent的事件是注册op_register，那么就将当前的socket注册到poller的selector上。
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public void run() { if (interestops == op_register) { try { // 核心代码，终于找到了！！！！！ // 当事件是注册的时候，将当前的niosocketchannel注册到poller的selector上。 socket.getiochannel().register( socket.getpoller().getselector(), selectionkey.op_read, socketwrapper); } catch (exception x) { log.error(sm.getstring("endpoint.nio.registerfail"), x); } } else { final selectionkey key = socket.getiochannel().keyfor(socket.getpoller().getselector()); try { if (key == null) { // the key was cancelled (e.g. due to socket closure) // and removed from the selector while it was being // processed. count down the connections at this point // since it won't have been counted down when the socket // closed. // selectionkey被取消的时候需要将selectionkey对应的endpoint的connection计数器，减一 socket.socketwrapper.getendpoint().countdownconnection(); ((niosocketwrapper) socket.socketwrapper).closed = true; } else { final niosocketwrapper socketwrapper = (niosocketwrapper) key.attachment(); if (socketwrapper != null) { //we are registering the key to start with, reset the fairness counter. int ops = key.interestops() | interestops; socketwrapper.interestops(ops); key.interestops(ops); } else { socket.getpoller().cancelledkey(key); } } } catch (cancelledkeyexception ckx) { try { socket.getpoller().cancelledkey(key); } catch (exception ignore) { } } } } |
（4）poller线程内会执行keycount = selector.select(selectortimeout);获取当前需要处理的selectionkey的数量，然后当keycount大于0时，会获取selector的迭代器，遍历所有需要的selectionkey，并对其进行处理。在这里将socket的事件封装成niosocketwrapper。
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// 得到selectedkeys的迭代器iterator<selectionkey> iterator = keycount > 0 ? selector.selectedkeys().iterator() : null; // 遍历所有的selectionkey，并对其进行处理 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() // 如果有attachment，就处理 if (socketwrapper != null) { // 处理事件 processkey(sk, socketwrapper); } } |
processkey在处理selectionkey，如果当前poller已经关闭，就取消key。selectionkey对应的channel如果发生读事件，就调用abatractendpoint.processsocket执行读操作processsocket(attachment, socketevent.open_read, true)，如果selectionkey对应的channel发生写事件，就执行processsocket(attachment, socketevent.open_write, true);读大于写。socket的事件处理调用的是abatractendpoint的processsocket方法。
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protected void processkey(selectionkey sk, niosocketwrapper attachment) { try { if (close) { // 如果poller已经关闭了，就取消key 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 // 读优于写 // 如果selectionkey对应的channel已经准备好了读 // 就对niosocketwrapper进行读操作 if (sk.isreadable()) { if (!processsocket(attachment, socketevent.open_read, true)) { closesocket = true; } } // 如果selectionkey对应的channel已经准备好了写 // 就对niosocketwrapper进行写操作 if (!closesocket && sk.iswritable()) { if (!processsocket(attachment, socketevent.open_write, true)) { closesocket = true; } } if (closesocket) { // 如果已经关闭了，就取消key cancelledkey(sk); } } } } |
abatractendpoint.processsocket方法首先从缓存中获取socketprocessor类，如果缓存中没有就创建一个，socketprocessorbase接口对应的就是nioendpoint.socketprocessor，也就是worker。将对应的socketprocessor类放入到线程池中执行。
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public boolean processsocket(socketwrapperbase<s> socketwrapper, socketevent event, boolean dispatch) { // 得到socket的处理器 // connector在构造函数里面已经指定了协议：org.apache.coyote.http11.http11nioprotocol。 socketprocessorbase<s> sc = processorcache.pop(); if (sc == null) { // 如果没有，就创建一个socket的处理器。创建的时候指定socketwrapper以及socket的事件。 sc = createsocketprocessor(socketwrapper, event); } else { sc.reset(socketwrapper, event); } //socket的处理交给了线程池去处理。 executor executor = getexecutor(); if (dispatch && executor != null) { executor.execute(sc); } else { sc.run(); } |
（5）nioendpoint.niosocketwrapper，是socket的封装类，增强类，将socket与其他对象建立关联。
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public static class niosocketwrapper extends socketwrapperbase<niochannel> { private final nioselectorpool pool; private poller poller = null; // 轮询的poller private int interestops = 0; private countdownlatch readlatch = null; private countdownlatch writelatch = null; private volatile sendfiledata sendfiledata = null; private volatile long lastread = system.currenttimemillis(); private volatile long lastwrite = lastread; private volatile boolean closed = false; |
（6）nioendpoint.socketprocessor（worker）继承了runnable接口，负责对socket的g各种事件进行处理。读事件、写事件、停止时间、超时事件、断连事件、错误时间、连接失败事件。
socketprocessor的dorun方法，会根据socketstate进行处理，socketstate 为stop、disconnect或者error的时候就进行关闭，socketwrapperbase对应的selector事件，得到指定的handler处理器进行处理。
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@override protected void dorun() { niochannel socket = socketwrapper.getsocket(); selectionkey key = socket.getiochannel().keyfor(socket.getpoller().getselector()); try { int handshake = -1; try { if (key != null) { if (socket.ishandshakecomplete()) { // 是否已经握手成功，不需要tls(加密)握手，就让处理器对socket和event的组合进行处理。 handshake = 0; } else if (event == socketevent.stop || event == socketevent.disconnect || event == socketevent.error) { // 不能够完成tls握手，就把他认为是tls握手失败。 handshake = -1; } else { handshake = socket.handshake(key.isreadable(), key.iswritable()); // the handshake process reads/writes from/to the // socket. status may therefore be open_write once // the handshake completes. however, the handshake // happens when the socket is opened so the status // must always be open_read after it completes. it // is ok to always set this as it is only used if // the handshake completes. // 握手从/向socket读/写时，握手一旦完成状态应该为open_write， // 握手是在套接字打开时发生的，因此在完成后状态必须始终为open_read // 始终设置此选项是可以的，因为它仅在握手完成时使用。 event = socketevent.open_read; } } } catch (ioexception x) { handshake = -1; if (log.isdebugenabled()) log.debug("error during ssl handshake", x); } catch (cancelledkeyexception ckx) { handshake = -1; } if (handshake == 0) { socketstate state = socketstate.open; // process the request from this socket if (event == null) { // 调用处理器进行处理。 // nioendpoint的默认handler是http11的 // 这里的handler是abstractprotocol.connectionhandler // 这个handler的设置方法是： // 首先在connector类的构造函数中，将默认的protocolhandler设置为org.apache.coyote.http11.http11nioprotocol // abstracthttp11protocol的构造函数里面创建了handler类connectionhandler state = gethandler().process(socketwrapper, socketevent.open_read); } else { state = gethandler().process(socketwrapper, event); } // 如果返回的状态是socketstate，那么就关掉连接 if (state == socketstate.closed) { close(socket, key); } } else if (handshake == -1) { gethandler().process(socketwrapper, socketevent.connect_fail); close(socket, key); } else if (handshake == selectionkey.op_read) { // 如果是selectionkey.op_read，也就是读事件的话，就将op_read时间设置到socketwrapper socketwrapper.registerreadinterest(); } else if (handshake == selectionkey.op_write) { // 如果是selectionkey.op_write，也就是读事件的话，就将op_write事件设置到socketwrapper socketwrapper.registerwriteinterest(); } |
二、connectionhandler
（1）connectionhandler用于根据socket连接找到相应的engine处理器。
上面是socketprocessor的dorun方法，执行了gethandler().process(socketwrapper, socketevent.open_read);;process方法是首先在map缓存中查找当前socket是否存在对应的processor，如果不存在，再去可循环的处理器栈中查找是否存在，如果不存在就创建相应的processor，然后将新创建的processor与socket建立映射，存在connection的map中。在任何一个阶段得到processor对象之后，会执行processor的process方法state = processor.process(wrapper, status);
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protected static class connectionhandler<s> implements abstractendpoint.handler<s> { private final abstractprotocol<s> proto; private final requestgroupinfo global = new requestgroupinfo(); private final atomiclong registercount = new atomiclong(0); // 终于找到了这个集合，给socket和处理器建立连接 // 对每个有效链接都会缓存进这里，用于连接选择一个合适的processor实现以进行请求处理。 private final map<s, processor> connections = new concurrenthashmap<>(); // 可循环的处理器栈 private final recycledprocessors recycledprocessors = new recycledprocessors(this); @override public socketstate process(socketwrapperbase<s> wrapper, socketevent status) { if (getlog().isdebugenabled()) { getlog().debug(sm.getstring("abstractconnectionhandler.process", wrapper.getsocket(), status)); } if (wrapper == null) { // wrapper == null 表示socket已经被关闭了，所以不需要做任何操作。 return socketstate.closed; } // 得到wrapper内的socket对象 s socket = wrapper.getsocket(); // 从map缓冲区中得到socket对应的处理器。 processor processor = connections.get(socket); if (getlog().isdebugenabled()) { getlog().debug(sm.getstring("abstractconnectionhandler.connectionsget", processor, socket)); } // timeouts are calculated on a dedicated thread and then // dispatched. because of delays in the dispatch process, the // timeout may no longer be required. check here and avoid // unnecessary processing. // 超时是在专用线程上计算的，然后被调度。 // 因为调度过程中的延迟，可能不再需要超时。检查这里，避免不必要的处理。 if (socketevent.timeout == status && (processor == null || !processor.isasync() && !processor.isupgrade() || processor.isasync() && !processor.checkasynctimeoutgeneration())) { // this is effectively a no-op return socketstate.open; } // 如果map缓存存在该socket相关的处理器 if (processor != null) { // make sure an async timeout doesn't fire // 确保没有触发异步超时 getprotocol().removewaitingprocessor(processor); } else if (status == socketevent.disconnect || status == socketevent.error) { // nothing to do. endpoint requested a close and there is no // longer a processor associated with this socket. // socketevent事件是关闭，或者socketevent时间出错，此时不需要做任何操作。 // endpoint需要一个closed的信号，并且这里不再有与这个socket有关联了 return socketstate.closed; } containerthreadmarker.set(); try { // map缓存不存在该socket相关的处理器 if (processor == null) { string negotiatedprotocol = wrapper.getnegotiatedprotocol(); // openssl typically returns null whereas jsse typically // returns "" when no protocol is negotiated // openssl通常返回null，而jsse通常在没有协议协商时返回"" if (negotiatedprotocol != null && negotiatedprotocol.length() > 0) { // 获取协商协议 upgradeprotocol upgradeprotocol = getprotocol().getnegotiatedprotocol(negotiatedprotocol); if (upgradeprotocol != null) { // 升级协议为空 processor = upgradeprotocol.getprocessor(wrapper, getprotocol().getadapter()); if (getlog().isdebugenabled()) { getlog().debug(sm.getstring("abstractconnectionhandler.processorcreate", processor)); } } else if (negotiatedprotocol.equals("http/1.1")) { // explicitly negotiated the default protocol. // obtain a processor below. } else { // todo: // openssl 1.0.2's alpn callback doesn't support // failing the handshake with an error if no // protocol can be negotiated. therefore, we need to // fail the connection here. once this is fixed, // replace the code below with the commented out // block. if (getlog().isdebugenabled()) { getlog().debug(sm.getstring("abstractconnectionhandler.negotiatedprocessor.fail", negotiatedprotocol)); } return socketstate.closed; /* * to replace the code above once openssl 1.1.0 is * used. // failed to create processor. this is a bug. throw new illegalstateexception(sm.getstring( "abstractconnectionhandler.negotiatedprocessor.fail", negotiatedprotocol)); */ } } } // 经过上面的操作，processor还是null的话。 if (processor == null) { // 从recycledprocessors可循环processors中获取processor processor = recycledprocessors.pop(); if (getlog().isdebugenabled()) { getlog().debug(sm.getstring("abstractconnectionhandler.processorpop", processor)); } } if (processor == null) { // 创建处理器 processor = getprotocol().createprocessor(); register(processor); if (getlog().isdebugenabled()) { getlog().debug(sm.getstring("abstractconnectionhandler.processorcreate", processor)); } } processor.setsslsupport( wrapper.getsslsupport(getprotocol().getclientcertprovider())); // 将socket和processor建立关联。 connections.put(socket, processor); socketstate state = socketstate.closed; do { // 调用processor的process方法。 state = processor.process(wrapper, status); // processor的process方法返回升级状态 if (state == socketstate.upgrading) { // get the http upgrade handler // 得到http的升级句柄 upgradetoken upgradetoken = processor.getupgradetoken(); // retrieve leftover input // 检索剩余输入 bytebuffer leftoverinput = processor.getleftoverinput(); if (upgradetoken == null) { // assume direct http/2 connection upgradeprotocol upgradeprotocol = getprotocol().getupgradeprotocol("h2c"); if (upgradeprotocol != null) { // release the http11 processor to be re-used release(processor); // create the upgrade processor processor = upgradeprotocol.getprocessor(wrapper, getprotocol().getadapter()); wrapper.unread(leftoverinput); // associate with the processor with the connection connections.put(socket, processor); } else { if (getlog().isdebugenabled()) { getlog().debug(sm.getstring( "abstractconnectionhandler.negotiatedprocessor.fail", "h2c")); } // exit loop and trigger appropriate clean-up state = socketstate.closed; } } else { httpupgradehandler httpupgradehandler = upgradetoken.gethttpupgradehandler(); // release the http11 processor to be re-used release(processor); // create the upgrade processor processor = getprotocol().createupgradeprocessor(wrapper, upgradetoken); if (getlog().isdebugenabled()) { getlog().debug(sm.getstring("abstractconnectionhandler.upgradecreate", processor, wrapper)); } wrapper.unread(leftoverinput); // associate with the processor with the connection connections.put(socket, processor); // initialise the upgrade handler (which may trigger // some io using the new protocol which is why the lines // above are necessary) // this cast should be safe. if it fails the error // handling for the surrounding try/catch will deal with // it. if (upgradetoken.getinstancemanager() == null) { httpupgradehandler.init((webconnection) processor); } else { classloader oldcl = upgradetoken.getcontextbind().bind(false, null); try { httpupgradehandler.init((webconnection) processor); } finally { upgradetoken.getcontextbind().unbind(false, oldcl); } } } } } while (state == socketstate.upgrading); 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（2）以http11协议为例，执行的是http11processor，http11processor的祖父类abstractprocessorlight实现了process方法，process调用了service模板方法，service模板方法是由http11processor进行实现的。service方法最重要的操作是执行getadapter().service(request, response);
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@override public socketstate service(socketwrapperbase<?> socketwrapper) throws ioexception { // 上面省略n行 // 调用coyote的service方法 getadapter().service(request, response); // 下面省略n行 |
三、coyote
回顾一下coyoteadapter的创建是在connector的initinternal方法。
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@override public socketstate service(socketwrapperbase<?> socketwrapper) throws ioexception { // 上面省略n行 // 调用coyote的service方法 getadapter().service(request, response); // 下面省略n行 |
coyote的作用就是coyote.request和coyote.rsponse转成httpservletrequest和httpservletrsponse。然后，因为connector在init的时候，将自己注入到了coyoteadapter中，所以，直接通过connector.getservice()方法就可以拿到service，然后从service开始调用责任链模式，进行处理。
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@override public socketstate service(socketwrapperbase<?> socketwrapper) throws ioexception { // 上面省略n行 // 调用coyote的service方法 getadapter().service(request, response); // 下面省略n行 |
四、容器责任链模式
接下来就是从standradengine开始的责任链模式。首先执行standradengine的责任链模式，找到合适的engine，合适的engine在通过责任链模式找到合适的context，直到找到standardwrappervalve。最后执行到standardwrappervalve的invoke方法。首先查看context和wrapper是不是不可用了，如果可用，并且servelt还没有被初始化，就执行初始化操作。如果是单线程模式就直接返回之前创建好的servelt，如果是多线程模式，就先创建一个servelt对象进行返回。
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@override public final void invoke(request request, response response) throws ioexception, servletexception { // 初始化我们需要的本地变量 boolean unavailable = false; throwable throwable = null; // this should be a request attribute... long t1 = system.currenttimemillis(); // 原子类atomicinteger，cas操作，表示请求的数量。 requestcount.incrementandget(); standardwrapper wrapper = (standardwrapper) getcontainer(); servlet servlet = null; context context = (context) wrapper.getparent(); // 检查当前的context应用是否已经被标注为不可以使用 if (!context.getstate().isavailable()) { // 如果当前应用不可以使用的话，就报503错误。 response.senderror(httpservletresponse.sc_service_unavailable, sm.getstring("standardcontext.isunavailable")); unavailable = true; } // 检查servelt是否被标记为不可使用 if (!unavailable && wrapper.isunavailable()) { container.getlogger().info(sm.getstring("standardwrapper.isunavailable", wrapper.getname())); long available = wrapper.getavailable(); if ((available > 0l) && (available < long.max_value)) { response.setdateheader("retry-after", available); response.senderror(httpservletresponse.sc_service_unavailable, sm.getstring("standardwrapper.isunavailable", wrapper.getname())); } else if (available == long.max_value) { response.senderror(httpservletresponse.sc_not_found, sm.getstring("standardwrapper.notfound", wrapper.getname())); } unavailable = true; } // servelt是第一次调用的时候初始化 try { if (!unavailable) { // 如果此时servelt还没有被初始化，就分配一个servelt实例来处理request请求。 servlet = wrapper.allocate(); } /// 省略代码.......................................... // // 给该request创建filter过滤链。filter过滤链执行完之后，会执行servelt applicationfilterchain filterchain = applicationfilterfactory.createfilterchain(request, wrapper, servlet); // call the filter chain for this request // note: this also calls the servlet's service() method try { if ((servlet != null) && (filterchain != null)) { // swallow output if needed if (context.getswallowoutput()) { try { systemloghandler.startcapture(); if (request.isasyncdispatching()) { request.getasynccontextinternal().dointernaldispatch(); } else { // 调用过滤链 filterchain.dofilter(request.getrequest(), response.getresponse()); } /// 省略代码.......................................... |
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原文链接：https://blog.csdn.net/qq_34037358/article/details/115579034
