前言
tomcat从架构上看，包含Service，Engine，Host，Context，Wrapper。那么，当用户发起一个请求时，tomcat是如何将url映射到具体的Wrapper上的呢?
Mapper组件机制
Tomcat 设计了 Mapper(映射)组件 完成 url和Host、Context、Wrapper等组件容器的映射。
Mapper组件的核心功能是提供请求路径的路由映射，根据某个请求路径通过计算得到相应的Servlet（Wrapper）。
与url到Wrapper映射相关的类位于org.apache.catalina.mapper包下，包含四个类：
- Mapper：映射关系最核心的、最重要的类。完成url与Host，Context，Wrapper映射关系的初始化、变更、存储及映射
- MapperListener：实现了ContainerListener与 LifecycleListener接口，监听tomcat组件的变化，当有Host，Context及Wrapper变更时，调用Mapper相关方法，增加或者删除Host，Context，Wrapper等。
- MappingData：url映射后的数据，表示一个url具体映射到哪个host，哪个context，哪个wrapper上。
- WrapperMappingInfo：表示一个Wrapper的信息，是一个普通的类，不太重要。
Mapper主要功能是完成url到Wrapper的映射，有三个主要的功能
- 1、映射关系存储：存储所有的Host，context及Wrapper的对应关系；
- 2、映射关系初始化及变更：当新增一个组件或者移除一个组件时，mapper如何维护url到Wrapper的映射关系；
- 3、映射关系使用：根据url，映射到具体的host，context和wrapper。
具体流程
请求连接和协议解析
- Connector组件的Endpoint中的Acceptor监听客户端套接字连接并接收Socket
- 将连接交给线程池Exectuor处理，开始执行请求响应任务
- Processor组件读取到消息报文，解析请求行、请求头、请求体，封装成Request对象
请求路由和处理
- Mapper组件根据请求行的URL值和请求头的Host值匹配由那个host、context、wrapper容器进行处理
- CoyoteAdaptor组件负责将Connector组件和Engine容器适配关联，把生成的Request对象和响应的Response对象传递给Engine容器，并调用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容器的管道开始同上流程处理，最后执行Content容器的Pipeline
- Content容器的管道开始同上流程处理，最后执行Wrapper容器的Pipeline
- Wrapper容器的管道开始同上流程处理
- 最后执行Wrapper容器对应的Servlet对象的处理方法
总体结论
一个Service有一个Engine，而一个Engine中有一个Mapper。根据Engine，Host，Context及Ｗrapper的对应关系，易得到以下的结论。
-
一个Ｍapper中，应该保存有多个Ｈost对象（的确是这样的，每个Ｈost对象称之为ＭappedＨost，多个ＭappedＨost以数组形式组合，各元素通过其name进行排序）
-
一个Ｈost对象包含多个context（Context在Mapper中定义为MappedContext，也是通过数组形式存在，并且元素根据ＭappedContext的命名排序。但是与组件不同的是，每一个Context可以有多个版本，因此每一个MappedContext 包含了多个ContextVersion，每一个MappedContext下的多个ContextVersion表示同一个Context的多个版本）
-
一个Context包含多个Wrapper（此处的Context在Mapper中为ContextVersion，包含多个Wrapper，这些Wrapper分成四类，精确匹配的Wrapper，前缀匹配的Wrapper，扩展名匹配的Wrapper，默认的Wrapper，在Mapper中，每一个Wrapper都通过一个MappedWrapper表示）
因此，Mapper的构成可以用下图表示 
当一个请求到来时，Mapper组件通过解析请求URL里的域名和路径，再到自己保存的 Map里去查找，就能定位到一个Servlet。请你注意，一个请求URL最后只会定位到一个 Wrapper容器，也就是一个Servlet。
从Tomcat的设计架构层面来分析Tomcat的请求处理。
步骤如下:
- 1、Connector组件Endpoint中的Acceptor监听客户端套接字连接并接收Socket。
- 2、将连接交给线程池Executor处理，开始执行请求响应任务。
- 3、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。
- 4、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。
- 5、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。
- 6、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。
- 7、Host容器的管道开始处理，流程类似，最后执行 Context容器的Pipeline。
- 8、Context容器的管道开始处理，流程类似，最后执行 Wrapper容器的Pipeline。
- 9、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 {
protected final String protocolHandlerClassName;
public Connector() {
this("org.apache.coyote.http11.Http11NioProtocol");
}
public Connector(String protocol) {
boolean aprConnector = AprLifecycleListener.isAprAvailable() &&
AprLifecycleListener.getUseAprConnector();
// 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
if ("HTTP/1.1".equals(protocol) || protocol == null) {
if (aprConnector) {
protocolHandlerClassName = "org.apache.coyote.http11.Http11AprProtocol";
} else {
protocolHandlerClassName = "org.apache.coyote.http11.Http11NioProtocol";
}
} else if ("AJP/1.3".equals(protocol)) {
if (aprConnector) {
protocolHandlerClassName = "org.apache.coyote.ajp.AjpAprProtocol";
} else {
protocolHandlerClassName = "org.apache.coyote.ajp.AjpNioProtocol";
}
} else {
protocolHandlerClassName = protocol;
}
// Instantiate protocol handler
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();
} catch (Exception e) {
log.error(sm.getString(
"coyoteConnector.protocolHandlerInstantiationFailed"), e);
} finally {
this.protocolHandler = p;
}
// Default for Connector depends on this system property
setThrowOnFailure(Boolean.getBoolean("org.apache.catalina.startup.EXIT_ON_INIT_FAILURE"));
}
// 初始化操作
@Override
protected void initInternal() throws LifecycleException {
super.initInternal();
if (protocolHandler == null) {
throw new LifecycleException(
sm.getString("coyoteConnector.protocolHandlerInstantiationFailed"));
}
// Initialize adapter
// 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);
if (service != null) {
protocolHandler.setUtilityExecutor(service.getServer().getUtilityExecutor());
}
// Make sure parseBodyMethodsSet has a default
if (null == parseBodyMethodsSet) {
setParseBodyMethods(getParseBodyMethods());
}
if (protocolHandler.isAprRequired() && !AprLifecycleListener.isInstanceCreated()) {
throw new LifecycleException(sm.getString("coyoteConnector.protocolHandlerNoAprListener",
getProtocolHandlerClassName()));
}
if (protocolHandler.isAprRequired() && !AprLifecycleListener.isAprAvailable()) {
throw new LifecycleException(sm.getString("coyoteConnector.protocolHandlerNoAprLibrary",
getProtocolHandlerClassName()));
}
if (AprLifecycleListener.isAprAvailable() && AprLifecycleListener.getUseOpenSSL() &&
protocolHandler instanceof AbstractHttp11JsseProtocol) {
AbstractHttp11JsseProtocol<?> jsseProtocolHandler =
(AbstractHttp11JsseProtocol<?>) protocolHandler;
if (jsseProtocolHandler.isSSLEnabled() &&
jsseProtocolHandler.getSslImplementationName() == null) {
// OpenSSL is compatible with the JSSE configuration, so use it if APR is available
jsseProtocolHandler.setSslImplementationName(OpenSSLImplementation.class.getName());
}
}
try {
// 执行 协议处理器初始化操作
protocolHandler.init();
} catch (Exception e) {
throw new LifecycleException(
sm.getString("coyoteConnector.protocolHandlerInitializationFailed"), e);
}
}
// 使用此 连接器处理 请求
@Override
protected void startInternal() throws LifecycleException {
// Validate settings before starting
// 验证端口
if (getPortWithOffset() < 0) {
throw new LifecycleException(sm.getString(
"coyoteConnector.invalidPort", Integer.valueOf(getPortWithOffset())));
}
// 设置生命周期状态值
setState(LifecycleState.STARTING);
try {
// 调用 协议处理器 start 方法
protocolHandler.start();
} catch (Exception e) {
throw new LifecycleException(
sm.getString("coyoteConnector.protocolHandlerStartFailed"), e);
}
}
}
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);
}
}
}
}
请求流程源码解析
在Tomcat的整体架构中，我们发现Tomcat中的各个组件各司其职，组件之间松耦合，确保了整体架构的可伸缩性和可拓展性，那么在组件内部，如何增强组件的灵活性和拓展性呢？ 在Tomcat中，每个Container组件采用责任链模式来完成具体的请求处理。
在Tomcat中定义了Pipeline 和 Valve 两个接口，Pipeline 用于构建责任链， 后者代表责 任链上的每个处理器。Pipeline 中维护了一个基础的Valve，它始终位于Pipeline的末端 （最后执行），封装了具体的请求处理和输出响应的过程。当然，我们也可以调用 addValve()方法， 为Pipeline 添加其他的Valve， 后添加的Valve 位于基础的Valve之 前，并按照添加顺序执行。Pipiline通过获得首个Valve来启动整合链条的执行 。
源码入口
- org.apache.tomcat.util.net.NioEndpoint#startInternal (启动完成,接收请求)
- org.apache.tomcat.util.net.NioEndpoint.Poller#run (处理接收的请求)
- org.apache.tomcat.util.net.NioEndpoint.Poller#processKey
- org.apache.tomcat.util.net.AbstractEndpoint#processSocket
执行AbstractEndpoint.processSocket
- org.apache.tomcat.util.net.AbstractEndpoint#processSocket
- 由Executor线程池执行业务SocketWrapperBase.run
- Connector组件的Endpoint中的Acceptor监听客户端套接字连接并接收Socket
public abstract class AbstractEndpoint<S,U> {
public boolean processSocket(SocketWrapperBase<S> socketWrapper,
SocketEvent event, boolean dispatch) {
try {
if (socketWrapper == null) {
return false;
}
SocketProcessorBase<S> sc = processorCache.pop();
if (sc == null) {
sc = createSocketProcessor(socketWrapper, event);
} else {
sc.reset(socketWrapper, event);
}
Executor executor = getExecutor();
if (dispatch && executor != null) {
executor.execute(sc);
} else {
sc.run();
}
} catch (RejectedExecutionException ree) {
getLog().warn(sm.getString("endpoint.executor.fail", socketWrapper) , ree);
return false;
} catch (Throwable t) {
ExceptionUtils.handleThrowable(t);
// This means we got an OOM or similar creating a thread, or that
// the pool and its queue are full
getLog().error(sm.getString("endpoint.process.fail"), t);
return false;
}
return true;
}
}
执行SocketWrapperBase.run
- org.apache.tomcat.util.net.SocketProcessorBase#run
- 调用doRun方法 ○ 执行3次握手 ○ 获取handler并进行请求处理
- 将连接交给线程池Exectuor处理，开始执行请求响应任务
public abstract class SocketProcessorBase<S> implements Runnable {
protected SocketWrapperBase<S> socketWrapper;
protected SocketEvent event;
@Override
public final void run() {
synchronized (socketWrapper) {
// It is possible that processing may be triggered for read and
// write at the same time. The sync above makes sure that processing
// does not occur in parallel. The test below ensures that if the
// first event to be processed results in the socket being closed,
// the subsequent events are not processed.
if (socketWrapper.isClosed()) {
return;
}
doRun();
}
}
protected abstract void doRun();
}
public class NioEndpoint extends AbstractJsseEndpoint<NioChannel,SocketChannel> {
protected class SocketProcessor extends SocketProcessorBase<NioChannel> {
public SocketProcessor(SocketWrapperBase<NioChannel> socketWrapper, SocketEvent event) {
super(socketWrapper, event);
}
@Override
protected void doRun() {
NioChannel socket = socketWrapper.getSocket();
SelectionKey key = socket.getIOChannel().keyFor(socket.getPoller().getSelector());
try {
//执行3次握手
int handshake = -1;
try {
if (key != null) {
if (socket.isHandshakeComplete()) {
// No TLS handshaking required. Let the handler
// process this socket / event combination.
handshake = 0;
} else if (event == SocketEvent.STOP || event == SocketEvent.DISCONNECT ||
event == SocketEvent.ERROR) {
// Unable to complete the TLS handshake. Treat it as
// if the handshake failed.
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.
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) {
state = getHandler().process(socketWrapper, SocketEvent.OPEN_READ);
} else {
//获取handler并进行请求处理
state = getHandler().process(socketWrapper, event);
}
if (state == SocketState.CLOSED) {
close(socket, key);
}
} else if (handshake == -1 ) {
close(socket, key);
} else if (handshake == SelectionKey.OP_READ){
socketWrapper.registerReadInterest();
} else if (handshake == SelectionKey.OP_WRITE){
socketWrapper.registerWriteInterest();
}
} catch (CancelledKeyException cx) {
socket.getPoller().cancelledKey(key);
} catch (VirtualMachineError vme) {
ExceptionUtils.handleThrowable(vme);
} catch (Throwable t) {
log.error(sm.getString("endpoint.processing.fail"), t);
socket.getPoller().cancelledKey(key);
} finally {
socketWrapper = null;
event = null;
//return to cache
if (running && !paused) {
processorCache.push(this);
}
}
}
}
}
执行AbstractProtocol.process
- 获取当前Processor
- 调用processor的process方法（在此Endpoint将请求的信息交给Processor）
- Processor组件读取到消息报文，解析请求行、请求头、请求体，封装成Request对象
public abstract class AbstractProtocol<S> implements ProtocolHandler,
MBeanRegistration {
public SocketState process(SocketWrapperBase<S> wrapper, SocketEvent status) {
S socket = wrapper.getSocket();
//拿到当前Processor
Processor processor = (Processor) wrapper.getCurrentProcessor();
//....
SocketState state = SocketState.CLOSED;
//调用processor的process方法
state = processor.process(wrapper, status);
//...
}
}
执行AbstractProcessorLight.process
- 执行dispatch或执行service方法
public abstract class AbstractProcessorLight implements Processor {
@Override
public SocketState process(SocketWrapperBase<?> socketWrapper, SocketEvent status)
throws IOException {
SocketState state = SocketState.CLOSED;
Iterator<DispatchType> dispatches = null;
do {
if (dispatches != null) {
DispatchType nextDispatch = dispatches.next();
//执行dispatch
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) {
//执行dispatch
state = dispatch(status);
if (state == SocketState.OPEN) {
// There may be pipe-lined data to read. If the data isn't
// processed now, execution will exit this loop and call
// release() which will recycle the processor (and input
// buffer) deleting any pipe-lined data. To avoid this,
// process it now.
state = service(socketWrapper);
}
} else if (status == SocketEvent.OPEN_WRITE) {
// Extra write event likely after async, ignore
state = SocketState.LONG;
} else if (status == SocketEvent.OPEN_READ){
//执行service方法
state = service(socketWrapper);
} else {
// Default to closing the socket if the SocketEvent passed in
// is not consistent with the current state of the Processor
state = SocketState.CLOSED;
}
if (getLog().isDebugEnabled()) {
getLog().debug("Socket: [" + socketWrapper +
"], Status in: [" + status +
"], State out: [" + state + "]");
}
if (state != SocketState.CLOSED && isAsync()) {
state = asyncPostProcess();
if (getLog().isDebugEnabled()) {
getLog().debug("Socket: [" + socketWrapper +
"], State after async post processing: [" + state + "]");
}
}
if (dispatches == null || !dispatches.hasNext()) {
// Only returns non-null iterator if there are
// dispatches to process.
dispatches = getIteratorAndClearDispatches();
}
} while (state == SocketState.ASYNC_END ||
dispatches != null && state != SocketState.CLOSED);
return state;
}
}public abstract class AbstractProcessorLight implements Processor {
@Override
public SocketState process(SocketWrapperBase<?> socketWrapper, SocketEvent status)
throws IOException {
SocketState state = SocketState.CLOSED;
Iterator<DispatchType> dispatches = null;
do {
if (dispatches != null) {
DispatchType nextDispatch = dispatches.next();
//执行dispatch
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) {
//执行dispatch
state = dispatch(status);
if (state == SocketState.OPEN) {
// There may be pipe-lined data to read. If the data isn't
// processed now, execution will exit this loop and call
// release() which will recycle the processor (and input
// buffer) deleting any pipe-lined data. To avoid this,
// process it now.
state = service(socketWrapper);
}
} else if (status == SocketEvent.OPEN_WRITE) {
// Extra write event likely after async, ignore
state = SocketState.LONG;
} else if (status == SocketEvent.OPEN_READ){
//执行service方法
state = service(socketWrapper);
} else {
// Default to closing the socket if the SocketEvent passed in
// is not consistent with the current state of the Processor
state = SocketState.CLOSED;
}
if (getLog().isDebugEnabled()) {
getLog().debug("Socket: [" + socketWrapper +
"], Status in: [" + status +
"], State out: [" + state + "]");
}
if (state != SocketState.CLOSED && isAsync()) {
state = asyncPostProcess();
if (getLog().isDebugEnabled()) {
getLog().debug("Socket: [" + socketWrapper +
"], State after async post processing: [" + state + "]");
}
}
if (dispatches == null || !dispatches.hasNext()) {
// Only returns non-null iterator if there are
// dispatches to process.
dispatches = getIteratorAndClearDispatches();
}
} while (state == SocketState.ASYNC_END ||
dispatches != null && state != SocketState.CLOSED);
return state;
}
}
执行Http11Processor.service
- org.apache.coyote.http11.Http11Processor#service
- 解析请求行、请求头、请求体，封装成Request对象
- 获取adapter（CoyoteAdaptor）,调用service方法
- CoyoteAdaptor组件负责将Connector组件和Engine容器适配关联
public class Http11Processor extends AbstractProcessor {
public SocketState service(SocketWrapperBase<?> socketWrapper) throws IOException {
//......
//获取adapter（CoyoteAdaptor）,调用service方法
getAdapter().service(request, response);
//......
}
}
执行CoyoteAdaptor.service
- 获取到Request和Response对象
- 调用容器，把生成的Request对象和响应的Response对象传递给Engine容器
public class CoyoteAdapter implements Adapter {
@Override
public void service(org.apache.coyote.Request req, org.apache.coyote.Response res)
throws Exception {
//获取到Request和Response对象
Request request = (Request) req.getNote(ADAPTER_NOTES);
Response response = (Response) res.getNote(ADAPTER_NOTES);
//......
postParseSuccess = postParseRequest(req, request, res, response);
if (postParseSuccess) {
//check valves if we support async
request.setAsyncSupported(
connector.getService().getContainer().getPipeline().isAsyncSupported());
// Calling the container
//调用容器，获取Engin管道阀Valve
connector.getService().getContainer().getPipeline().getFirst().invoke(
request, response);
}
//......
}
}
执行责任链xxxValve.invoke
- 执行StandardServiceValve.invoke
- a. 获取Host，调用Host容器的Pipeline
- b. 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
- 执行StandardHostValve.invoke
- a. 获取Context,调用Context容器的Pipeline
- 执行StandardContextValve.invoke
- a. 获取Wrapper，调用Wrapper容器的Pipeline
获取Servlet – Wrapper.invoke
- 从Container中获取Wrapper
- 从Wrapper中获取到Servlet，至此拿到的就是具体业务Servlet
- 将Servlet封装到构造的FilterChain过滤器链中
- 执行过滤器链中的filter，并传入ServletRequest和ServletResponse
final class StandardWrapperValve extends ValveBase {
@Override
public final void invoke(Request request, Response response)
throws IOException, ServletException {
//......
//从Container中获取Wrapper
StandardWrapper wrapper = (StandardWrapper) getContainer();
Servlet servlet = null;
Context context = (Context) wrapper.getParent();
//......
//获取到servlet
servlet = wrapper.allocate();
//将Servlet封装到FilterChain过滤器链中
ApplicationFilterChain filterChain = ApplicationFilterFactory.createFilterChain(request, wrapper, servlet);
//......
//执行过滤器链中的filter
filterChain.doFilter(request.getRequest(),response.getResponse());
//......
}
}
执行过滤器链中的filter
- 获取到ServletRequest、ServletResponse执行过滤器
- 调用servlet.service方法
- 调用HttpServlet.service ○ 执行doGet、doPost方法
public final class ApplicationFilterChain implements FilterChain {
@Override
public void doFilter(ServletRequest request, ServletResponse response)
throws IOException, ServletException {
//......
internalDoFilter(request,response);
}
private void internalDoFilter(ServletRequest request, ServletResponse response)
throws IOException, ServletException {
//......
//执行过滤器
//调用Servlet.service方法
servlet.service(request, response);
//......
}
}
执行HttpServlet.service
- 获取请求方式
- 执行对应的请求方法，如：doPost、doGet等
public abstract class HttpServlet extends GenericServlet {
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
//获取请求方式
String method = req.getMethod();
//执行对应的请求方法
if (method.equals(METHOD_GET)) {
long lastModified = getLastModified(req);
if (lastModified == -1) {
// servlet doesn't support if-modified-since, no reason
// to go through further expensive logic
doGet(req, resp);
} else {
long ifModifiedSince;
try {
ifModifiedSince = req.getDateHeader(HEADER_IFMODSINCE);
} catch (IllegalArgumentException iae) {
// Invalid date header - proceed as if none was set
ifModifiedSince = -1;
}
if (ifModifiedSince < (lastModified / 1000 * 1000)) {
// If the servlet mod time is later, call doGet()
// Round down to the nearest second for a proper compare
// A ifModifiedSince of -1 will always be less
maybeSetLastModified(resp, lastModified);
doGet(req, resp);
} else {
resp.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
}
}
} else if (method.equals(METHOD_HEAD)) {
long lastModified = getLastModified(req);
maybeSetLastModified(resp, lastModified);
doHead(req, resp);
} else if (method.equals(METHOD_POST)) {
doPost(req, resp);
} else if (method.equals(METHOD_PUT)) {
doPut(req, resp);
} else if (method.equals(METHOD_DELETE)) {
doDelete(req, resp);
} else if (method.equals(METHOD_OPTIONS)) {
doOptions(req,resp);
} else if (method.equals(METHOD_TRACE)) {
doTrace(req,resp);
} else {
//
// Note that this means NO servlet supports whatever
// method was requested, anywhere on this server.
//
String errMsg = lStrings.getString("http.method_not_implemented");
Object[] errArgs = new Object[1];
errArgs[0] = method;
errMsg = MessageFormat.format(errMsg, errArgs);
resp.sendError(HttpServletResponse.SC_NOT_IMPLEMENTED, errMsg);
}
}
}
Http长连接的支持
- 客户端请求会携带Connection: keep-alive
- service方法会解析,并使用keepAlive参数记录是否满足长连接条件
- 不满足长连接条件则返回的响应头携带Connection: close,表示关闭连接
- 满足长连接条件则不返回Connection参数
public class Http11Processor extends AbstractProcessor {
@Override
public SocketState service(SocketWrapperBase<?> socketWrapper)
throws IOException {
RequestInfo rp = request.getRequestProcessor();
rp.setStage(org.apache.coyote.Constants.STAGE_PARSE);
// Setting up the I/O
setSocketWrapper(socketWrapper);
inputBuffer.init(socketWrapper);
outputBuffer.init(socketWrapper);
// Flags
keepAlive = true;
openSocket = false;
readComplete = true;
boolean keptAlive = false;
SendfileState sendfileState = SendfileState.DONE;
//控制tomcat长连接原理 while循环 keepAlive
while (!getErrorState().isError() && keepAlive && !isAsync() && upgradeToken == null &&
sendfileState == SendfileState.DONE && !protocol.isPaused()) {
// Parsing the request header
try {
if (!inputBuffer.parseRequestLine(keptAlive, protocol.getConnectionTimeout(),
protocol.getKeepAliveTimeout())) {
if (inputBuffer.getParsingRequestLinePhase() == -1) {
return SocketState.UPGRADING;
} else if (handleIncompleteRequestLineRead()) {
break;
}
}
if (protocol.isPaused()) {
// 503 - Service unavailable
response.setStatus(503);
setErrorState(ErrorState.CLOSE_CLEAN, null);
} else {
keptAlive = true;
// Set this every time in case limit has been changed via JMX
request.getMimeHeaders().setLimit(protocol.getMaxHeaderCount());
if (!inputBuffer.parseHeaders()) {
// We've read part of the request, don't recycle it
// instead associate it with the socket
openSocket = true;
readComplete = false;
break;
}
if (!protocol.getDisableUploadTimeout()) {
socketWrapper.setReadTimeout(protocol.getConnectionUploadTimeout());
}
}
} catch (IOException e) {
if (log.isDebugEnabled()) {
log.debug(sm.getString("http11processor.header.parse"), e);
}
setErrorState(ErrorState.CLOSE_CONNECTION_NOW, e);
break;
} catch (Throwable t) {
ExceptionUtils.handleThrowable(t);
UserDataHelper.Mode logMode = userDataHelper.getNextMode();
if (logMode != null) {
String message = sm.getString("http11processor.header.parse");
switch (logMode) {
case INFO_THEN_DEBUG:
message += sm.getString("http11processor.fallToDebug");
//$FALL-THROUGH$
case INFO:
log.info(message, t);
break;
case DEBUG:
log.debug(message, t);
}
}
// 400 - Bad Request
response.setStatus(400);
setErrorState(ErrorState.CLOSE_CLEAN, t);
}
// 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 = protocol.getUpgradeProtocol(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(
socketWrapper, getAdapter(), cloneRequest(request));
UpgradeToken upgradeToken = new UpgradeToken(upgradeHandler, null, null);
action(ActionCode.UPGRADE, upgradeToken);
return SocketState.UPGRADING;
}
}
}
if (getErrorState().isIoAllowed()) {
// Setting up filters, and parse some request headers
rp.setStage(org.apache.coyote.Constants.STAGE_PREPARE);
try {
prepareRequest();
} catch (Throwable t) {
ExceptionUtils.handleThrowable(t);
if (log.isDebugEnabled()) {
log.debug(sm.getString("http11processor.request.prepare"), t);
}
// 500 - Internal Server Error
response.setStatus(500);
setErrorState(ErrorState.CLOSE_CLEAN, t);
}
}
//最大活跃的http请求数量
int maxKeepAliveRequests = protocol.getMaxKeepAliveRequests();
if (maxKeepAliveRequests == 1) {
keepAlive = false;
} else if (maxKeepAliveRequests > 0 &&
socketWrapper.decrementKeepAlive() <= 0) {
keepAlive = false;
}
// Process the request in the adapter
if (getErrorState().isIoAllowed()) {
try {
rp.setStage(org.apache.coyote.Constants.STAGE_SERVICE);
getAdapter().service(request, response);
// Handle when the response was committed before a serious
// error occurred. Throwing a ServletException should both
// set the status to 500 and set the errorException.
// If we fail here, then the response is likely already
// committed, so we can't try and set headers.
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) {
log.error(sm.getString("http11processor.request.process"), e);
// The response should not have been committed but check it
// anyway to be safe
if (response.isCommitted()) {
setErrorState(ErrorState.CLOSE_NOW, e);
} else {
response.reset();
response.setStatus(500);
setErrorState(ErrorState.CLOSE_CLEAN, e);
response.setHeader("Connection", "close"); // TODO: Remove
}
} catch (Throwable t) {
ExceptionUtils.handleThrowable(t);
log.error(sm.getString("http11processor.request.process"), 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()) {
// If this is an async request then the request ends when it has
// been completed. The AsyncContext is responsible for calling
// endRequest() in that case.
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 (!protocol.getDisableUploadTimeout()) {
int connectionTimeout = protocol.getConnectionTimeout();
if(connectionTimeout > 0) {
socketWrapper.setReadTimeout(connectionTimeout);
} else {
socketWrapper.setReadTimeout(0);
}
}
rp.setStage(org.apache.coyote.Constants.STAGE_KEEPALIVE);
sendfileState = processSendfile(socketWrapper);
}
rp.setStage(org.apache.coyote.Constants.STAGE_ENDED);
if (getErrorState().isError() || protocol.isPaused()) {
return SocketState.CLOSED;
} else if (isAsync()) {
return SocketState.LONG;
} else if (isUpgrade()) {
return SocketState.UPGRADING;
} else {
if (sendfileState == SendfileState.PENDING) {
return SocketState.SENDFILE;
} else {
if (openSocket) {
if (readComplete) {
return SocketState.OPEN;
} else {
return SocketState.LONG;
}
} else {
return SocketState.CLOSED;
}
}
}
}
}
参考： https://www.cnblogs.com/wansw/p/10244039.html
https://blog.csdn.net/nblife0000/article/details/60364847
https://blog.csdn.net/jiaomingliang/article/details/47414657
https://blog.csdn.net/nmjhehe/article/details/115533383
https://blog.csdn.net/qq_44377709/article/details/122833521
https://blog.csdn.net/weixin_42413454/article/details/125585199