Tomcat源码分析
一 tomcat架构图
1.1 宏观架构
Tomcat中最顶层的容器是Server，代表着整个服务器，从上图中可以看出，一个Server可以包含至少一个Service，用于具体提供服务。
Service主要包含两个部分：Connector和Container。从上图中可以看出 Tomcat 的心脏就是这两个组件，他们的作用如下：
- Connector用于处理连接相关的事情，并提供Socket与Request和Response相关的转化;
- Container用于封装和管理Servlet，以及具体处理Request请求；
一个Tomcat中只有一个Server，一个Server可以包含多个Service，一个Service只有一个Container，但是可以有多个Connectors，这是因为一个服务可以有多个连接，如同时提供Http和Https链接，也可以提供向相同协议不同端口的连接,示意图如下（Engine、Host、Context下边会说到）
多个 Connector 和一个 Container 就形成了一个 Service，有了 Service 就可以对外提供服务了，但是 Service 还要一个生存的环境，必须要有人能够给她生命、掌握其生死大权，那就非 Server 莫属了！所以整个 Tomcat 的生命周期由 Server 控制。
另外，上述的包含关系或者说是父子关系，都可以在tomcat的conf目录下的server.xml配置文件中看出，下图是删除了注释内容之后的一个完整的server.xml配置文件
上边的配置文件，还可以通过下边的一张结构图更清楚的理解：
1.Tomcat中只有一个Server，一个Server可以有多个Service，一个Service可以有多个Connector和一个Container；
2. Server掌管着整个Tomcat的生死大权；
3. Service 是对外提供服务的；
4. Connector用于接受请求并将请求封装成Request和Response来具体处理；
5. Container用于封装和管理Servlet，以及具体处理request请求；
由上述内容我们大致可以知道一个请求发送到Tomcat之后，首先经过Service然后会交给我们的Connector，Connector用于接收请求并将接收的请求封装为Request和Response来具体处理，Request和Response封装完之后再交由Container进行处理，Container处理完请求之后再返回给Connector，最后在由Connector通过Socket将处理的结果返回给客户端，这样整个请求的流程就处理完了！
Connector最底层使用的是Socket来进行连接的，Request和Response是按照HTTP协议来封装的，所以Connector同时需要实现TCP/IP协议和HTTP协议！
Tomcat既然处理请求，那么肯定需要先接收到这个请求，接收请求这个东西我们首先就需要看一下Connector！
Connector就是使用ProtocolHandler来处理请求的，不同的ProtocolHandler代表不同的连接类型，比如：Http11Protocol使用的是普通Socket来连接的，Http11NioProtocol使用的是NioSocket来连接的。
其中ProtocolHandler由包含了三个部件：Endpoint、Processor、Adapter。
（1）Endpoint用来处理底层Socket的网络连接，Processor用于将Endpoint接收到的Socket封装成Request，Adapter用于将Request交给Container进行具体的处理。
（2）Endpoint由于是处理底层的Socket网络连接，因此Endpoint是用来实现TCP/IP协议的，而Processor用来实现HTTP协议的，Adapter将请求适配到Servlet容器进行具体的处理。
（3）Endpoint的抽象实现AbstractEndpoint里面定义的Acceptor和AsyncTimeout两个内部类和一个Handler接口。Acceptor用于监听请求，AsyncTimeout用于检查异步Request的超时，Handler用于处理接收到的Socket，在内部调用Processor进行处理。
1.2 容器架构
Container用于封装和管理Servlet，以及具体处理Request请求，在Connector内部包含了4个子容器4个子容器的作用分别是：
（1）Engine：引擎，用来管理多个站点，一个Service最多只能有一个Engine；
（2）Host：代表一个站点，也可以叫虚拟主机，通过配置Host就可以添加站点；
（3）Context：代表一个应用程序，对应着平时开发的一套程序，或者一个WEB-INF目录以及下面的web.xml文件；
（4）Wrapper：每一Wrapper封装着一个Servlet；
二 tomcat请求执行流程
三tomcat代码代码包装
Server{
Service[]{ //服务
Connector[]: //连接器 监听端口
Engin:{ //控制处理逻辑
Host[]:{ //虚拟主机 映射域
Context[]:{//web应用
Wapper[]:{} //servlert服务接口
}
}
}
}
}四tomcat类结构
如上图所示是tomcat的类的模型图.
如上所示是tomcat的实际的类结构图,可以看出实际上有两个超级接口分别是lifecycle,和container接口.lifecycle接口决定类整个自容器与组建的生命周期函数.整个contaier接口绝定了管道,管道中包含了阀门.具体这里是怎么个使用关系后面再详细讲解.容器的特点就是有几个特别的方法，首先容器是lifecycle的生命周期子类。那么他包含了几个方法分别是
addChild(Container child) :添加子容器
Container getParent() :获取父容器
Pipeline getPipeline():获取管道
Pipeline里面有Value阀门，阀门可以预处理请求
五 tomcat请求处理模型
5.1 Connector的protocol
Connector在处理HTTP请求时，会使用不同的protocol。不同的Tomcat版本支持的protocol不同，其中最典型的protocol包括BIO、NIO和APR（Tomcat7中支持这3种，Tomcat8增加了对NIO2的支持，而到了Tomcat8.5和Tomcat9.0，则去掉了对BIO的支持）。
BIO是Blocking IO，顾名思义是阻塞的IO；NIO是Non-blocking IO，则是非阻塞的IO。而APR是Apache Portable Runtime，是Apache可移植运行库，利用本地库可以实现高可扩展性、高性能；Apr是在Tomcat上运行高并发应用的首选模式，但是需要安装apr、apr-utils、tomcat-native等包
5.2如何指定protocol
Connector使用哪种protocol，可以通过<connector>元素中的protocol属性进行指定，也可以使用默认值。
指定的protocol取值及对应的协议如下：
HTTP/1.1：默认值，使用的协议与Tomcat版本有关
org.apache.coyote.http11.Http11Protocol：BIO
org.apache.coyote.http11.Http11NioProtocol：NIO
org.apache.coyote.http11.Http11Nio2Protocol：NIO2
org.apache.coyote.http11.Http11AprProtocol：APR
如果没有指定protocol，则使用默认值HTTP/1.1，其含义如下：在Tomcat7中，自动选取使用BIO或APR（如果找到APR需要的本地库，则使用APR，否则使用BIO）；在Tomcat8中，自动选取使用NIO或APR（如果找到APR需要的本地库，则使用APR，否则使用NIO）
5.3请求处理流程
无论是BIO，还是NIO，Connector处理请求的大致流程是一样的：
在accept队列中接收连接（当客户端向服务器发送请求时，如果客户端与OS完成三次握手建立了连接，则OS将该连接放入accept队列）；在连接中获取请求的数据，生成request；调用servlet容器处理请求；返回response。为了便于后面的说明，首先明确一下连接与请求的关系：连接是TCP层面的（传输层），对应socket；请求是HTTP层面的（应用层），必须依赖于TCP的连接实现；一个TCP连接中可能传输多个HTTP请求。
在BIO实现的Connector中，处理请求的主要实体是JIoEndpoint对象。JIoEndpoint维护了Acceptor和Worker：Acceptor接收socket，然后从Worker线程池中找出空闲的线程处理socket，如果worker线程池没有空闲线程，则Acceptor将阻塞。其中Worker是Tomcat自带的线程池，如果通过<Executor>配置了其他线程池，原理与Worker类似。
在NIO实现的Connector中，处理请求的主要实体是NIoEndpoint对象。NIoEndpoint中除了包含Acceptor和Worker外，还使用了Poller
Acceptor接收socket后，不是直接使用Worker中的线程处理请求，而是先将请求发送给了Poller，而Poller是实现NIO的关键。Acceptor向Poller发送请求通过队列实现，使用了典型的生产者-消费者模式。在Poller中，维护了一个Selector对象；当Poller从队列中取出socket后，注册到该Selector中；然后通过遍历Selector，找出其中可读的socket，并使用Worker中的线程处理相应请求。与BIO类似，Worker也可以被自定义的线程池代替。
通过上述过程可以看出，在NIoEndpoint处理请求的过程中，无论是Acceptor接收socket，还是线程处理请求，使用的仍然是阻塞方式；但在“读取socket并交给Worker中的线程”的这个过程中，使用非阻塞的NIO实现，在并发量较大的情形下可以带来Tomcat效率的显著提升：
目前大多数HTTP请求使用的是长连接（HTTP/1.1默认keep-alive为true），而长连接意味着，一个TCP的socket在当前请求结束后，如果没有新的请求到来，socket不会立马释放，而是等timeout后再释放。如果使用BIO，“读取socket并交给Worker中的线程”这个过程是阻塞的，也就意味着在socket等待下一个请求或等待释放的过程中，处理这个socket的工作线程会一直被占用，无法释放；因此Tomcat可以同时处理的socket数目不能超过最大线程数，性能受到了极大限制。而使用NIO，“读取socket并交给Worker中的线程”这个过程是非阻塞的，当socket在等待下一个请求或等待释放时，并不会占用工作线程，因此Tomcat可以同时处理的socket数目远大于最大线程数，并发性能大大提高。
5.4内核模型与调用时序
- 指定 Protocol，初始化相应的 Endpoint，我们分析的是 NioEndpoint；
- init 过程：在 NioEndpoint 中做 bind 操作；
- start 过程：启动 worker 线程池，启动 1 个 Acceptor 和 2 个 Poller，当然它们都是默认值，可配；
- Acceptor 获取到新的连接后，getPoller0() 获取其中一个 Poller，然后 register 到 Poller 中；
- Poller 循环 selector.select(xxx)，如果有通道 readable，那么在 processKey 中将其放到 worker 线程池中。
如上是tomcat的线程模型.
六 tomcat启动和线程处理流程
如上图所示是tomcat的整个启动过程.下面我们根据上图来跟踪一下源代码的启动流程.如下图所示先是走bootstrap的main函数启动流程.
public static void main(String args[]) {
synchronized (daemonLock) {
if (daemon == null) {
Bootstrap bootstrap = new Bootstrap();
try {
bootstrap.init();
} catch (Throwable t) {
handleThrowable(t);
t.printStackTrace();
return;
}
daemon = bootstrap;
} else {
Thread.currentThread().setContextClassLoader(daemon.catalinaLoader);
}
}
try {
String command = "start";
if (args.length > 0) {
command = args[args.length - 1];
}
if (command.equals("startd")) {
args[args.length - 1] = "start";
daemon.load(args);
daemon.start();
} else if (command.equals("stopd")) {
args[args.length - 1] = "stop";
daemon.stop();
} else if (command.equals("start")) {
daemon.setAwait(true);
daemon.load(args);
daemon.start();
if (null == daemon.getServer()) {
System.exit(1);
}
} else if (command.equals("stop")) {
daemon.stopServer(args);
} else if (command.equals("configtest")) {
daemon.load(args);
if (null == daemon.getServer()) {
System.exit(1);
}
System.exit(0);
} else {
log.warn("Bootstrap: command \"" + command + "\" does not exist.");
}
} catch (Throwable t) {
// Unwrap the Exception for clearer error reporting
if (t instanceof InvocationTargetException &&
t.getCause() != null) {
t = t.getCause();
}
handleThrowable(t);
t.printStackTrace();
System.exit(1);
}
}6.1 daemon.load(args)
如上代码所示就是bootstrap的启动流程.它调用了load()和start()方法,那么我们来看看load()方法做了什么
private void load(String[] arguments) throws Exception {
String methodName = "load";
Object param[];
Class<?> paramTypes[];
if (arguments==null || arguments.length==0) {
paramTypes = null;
param = null;
} else {
paramTypes = new Class[1];
paramTypes[0] = arguments.getClass();
param = new Object[1];
param[0] = arguments;
}
Method method =
catalinaDaemon.getClass().getMethod(methodName, paramTypes);
if (log.isDebugEnabled()) {
log.debug("Calling startup class " + method);
}
method.invoke(catalinaDaemon, param);
}catalinaDaemon 调用了load()/start()方法的内部实现类都是这个,那么这个类是做什么呢.来看一下如下所示可以看出来,这个类就是 org.apache.catalina.startup.Catalina就是这个类,那么这个类做类什么的load()和start()方法做了什么呢
public void init() throws Exception {
initClassLoaders();
Thread.currentThread().setContextClassLoader(catalinaLoader);
SecurityClassLoad.securityClassLoad(catalinaLoader);
if (log.isDebugEnabled()) {
log.debug("Loading startup class");
}
Class<?> startupClass = catalinaLoader.loadClass("org.apache.catalina.startup.Catalina");
Object startupInstance = startupClass.getConstructor().newInstance();
if (log.isDebugEnabled()) {
log.debug("Setting startup class properties");
}
String methodName = "setParentClassLoader";
Class<?> paramTypes[] = new Class[1];
paramTypes[0] = Class.forName("java.lang.ClassLoader");
Object paramValues[] = new Object[1];
paramValues[0] = sharedLoader;
Method method = startupInstance.getClass().getMethod(methodName, paramTypes);
method.invoke(startupInstance, paramValues);
catalinaDaemon = startupInstance;
}再接着看load()方法.
public void load() {
if (loaded) {
return;
}
loaded = true;
long t1 = System.nanoTime();
initDirs();
initNaming();
Digester digester = createStartDigester();
InputSource inputSource = null;
InputStream inputStream = null;
File file = null;
try {
try {
file = configFile();
inputStream = new FileInputStream(file);
inputSource = new InputSource(file.toURI().toURL().toString());
} catch (Exception e) {
if (log.isDebugEnabled()) {
log.debug(sm.getString("catalina.configFail", file), e);
}
}
if (inputStream == null) {
try {
inputStream = getClass().getClassLoader()
.getResourceAsStream(getConfigFile());
inputSource = new InputSource
(getClass().getClassLoader()
.getResource(getConfigFile()).toString());
} catch (Exception e) {
if (log.isDebugEnabled()) {
log.debug(sm.getString("catalina.configFail",
getConfigFile()), e);
}
}
}
if (inputStream == null) {
try {
inputStream = getClass().getClassLoader()
.getResourceAsStream("server-embed.xml");
inputSource = new InputSource
(getClass().getClassLoader()
.getResource("server-embed.xml").toString());
} catch (Exception e) {
if (log.isDebugEnabled()) {
log.debug(sm.getString("catalina.configFail",
"server-embed.xml"), e);
}
}
}
if (inputStream == null || inputSource == null) {
if (file == null) {
log.warn(sm.getString("catalina.configFail",
getConfigFile() + "] or [server-embed.xml]"));
} else {
log.warn(sm.getString("catalina.configFail",
file.getAbsolutePath()));
if (file.exists() && !file.canRead()) {
log.warn("Permissions incorrect, read permission is not allowed on the file.");
}
}
return;
}
try {
inputSource.setByteStream(inputStream);
digester.push(this);
digester.parse(inputSource);
} catch (SAXParseException spe) {
log.warn("Catalina.start using " + getConfigFile() + ": " +
spe.getMessage());
return;
} catch (Exception e) {
log.warn("Catalina.start using " + getConfigFile() + ": " , e);
return;
}
} finally {
if (inputStream != null) {
try {
inputStream.close();
} catch (IOException e) { }
}
}
getServer().setCatalina(this);
getServer().setCatalinaHome(Bootstrap.getCatalinaHomeFile());
getServer().setCatalinaBase(Bootstrap.getCatalinaBaseFile());
initStreams();
try {
getServer().init();
} catch (LifecycleException e) {
if (Boolean.getBoolean("org.apache.catalina.startup.EXIT_ON_INIT_FAILURE")) {
throw new java.lang.Error(e);
} else {
log.error("Catalina.start", e);
}
}
long t2 = System.nanoTime();
if(log.isInfoEnabled()) {
log.info("Initialization processed in " + ((t2 - t1) / 1000000) + " ms");
}
}如上代码所示这个代码也算比较核心的代码了那么做了什么呢
1 一个是加载 server.xml文件.file = configFile();并实例化成为类.
2 getServer().setCatalina(this);/getServer().init(); 第二个就是每一个catalina对应一个server,然后调用server的init()方法对容器进行启动.
@Override
protected void initInternal() throws LifecycleException {
super.initInternal();
onameStringCache = register(new StringCache(), "type=StringCache");
MBeanFactory factory = new MBeanFactory();
factory.setContainer(this);
onameMBeanFactory = register(factory, "type=MBeanFactory");
globalNamingResources.init();
if (getCatalina() != null) {
ClassLoader cl = getCatalina().getParentClassLoader();
while (cl != null && cl != ClassLoader.getSystemClassLoader()) {
if (cl instanceof URLClassLoader) {
URL[] urls = ((URLClassLoader) cl).getURLs();
for (URL url : urls) {
if (url.getProtocol().equals("file")) {
try {
File f = new File (url.toURI());
if (f.isFile() &&
f.getName().endsWith(".jar")) {
ExtensionValidator.addSystemResource(f);
}
} catch (URISyntaxException | IOException e) {
}
}
}
}
cl = cl.getParent();
}
}
for (Service service : services) {
service.init();
}
}getServer().init() 可以看到核心代码,如上所示service.init()
@Override
protected void initInternal() throws LifecycleException {
super.initInternal();
if (engine != null) {
engine.init();
}
for (Executor executor : findExecutors()) {
if (executor instanceof JmxEnabled) {
((JmxEnabled) executor).setDomain(getDomain());
}
executor.init();
}
mapperListener.init();
synchronized (connectorsLock) {
for (Connector connector : connectors) {
try {
connector.init();
} catch (Exception e) {
String message = sm.getString(
"standardService.connector.initFailed", connector);
log.error(message, e);
if (Boolean.getBoolean("org.apache.catalina.startup.EXIT_ON_INIT_FAILURE")) {
throw new LifecycleException(message);
}
}
}
}
}可以看到如上代码所示,service.init()里面主要做了几件事情分别是
engine.init()
executor.init();
connector.init();
也就是说service初始化的时候分别对engine/executor/connector进行了相应的初始化工作.这里面主要是创建的worker线程池.我们重点看一下connector.init()方法做了什么.
@Override
protected void initInternal() throws LifecycleException {
super.initInternal();
adapter = new CoyoteAdapter(this);
protocolHandler.setAdapter(adapter);
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) {
jsseProtocolHandler.setSslImplementationName(OpenSSLImplementation.class.getName());
}
}
try {
protocolHandler.init();
} catch (Exception e) {
throw new LifecycleException(
sm.getString("coyoteConnector.protocolHandlerInitializationFailed"), e);
}
}如上代码片短所示,connector的init方法主要是adapter = new CoyoteAdapter(this);为protocalHandler添加了一个适配器的类,那么这个适配器的类做了什么呢.我们再往看 protocolHandler.init();
public void init() throws Exception {
if (getLog().isInfoEnabled()) {
getLog().info(sm.getString("abstractProtocolHandler.init", getName()));
}
if (oname == null) {
oname = createObjectName();
if (oname != null) {
Registry.getRegistry(null, null).registerComponent(this, oname, null);
}
}
if (this.domain != null) {
ObjectName rgOname = new ObjectName(domain + ":type=GlobalRequestProcessor,name=" + getName());
this.rgOname = rgOname;
Registry.getRegistry(null, null).registerComponent(
getHandler().getGlobal(), rgOname, null);
}
String endpointName = getName();
endpoint.setName(endpointName.substring(1, endpointName.length()-1));
endpoint.setDomain(domain);
endpoint.init();
}
endpoint.init() //endpoint.init()方法
public void init() throws Exception {
if (bindOnInit) {
bind();
bindState = BindState.BOUND_ON_INIT;
}
if (this.domain != null) {
oname = new ObjectName(domain + ":type=ThreadPool,name=\"" + getName() + "\"");
Registry.getRegistry(null, null).registerComponent(this, oname, null);
ObjectName socketPropertiesOname = new ObjectName(domain +
":type=SocketProperties,name=\"" + getName() + "\"");
socketProperties.setObjectName(socketPropertiesOname);
Registry.getRegistry(null, null).registerComponent(socketProperties, socketPropertiesOname, null);
for (SSLHostConfig sslHostConfig : findSslHostConfigs()) {
registerJmx(sslHostConfig);
}
}
}如上代码片段所示核心代码主要是bind();我们来看看bind()主要做了什么.这里可以看出来是绑定了IP地址和端口号
public void bind() throws Exception {
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 {
Channel ic = System.inheritedChannel();
if (ic instanceof ServerSocketChannel) {
serverSock = (ServerSocketChannel) ic;
}
if (serverSock == null) {
throw new IllegalArgumentException(sm.getString("endpoint.init.bind.inherited"));
}
}
serverSock.configureBlocking(true);
if (acceptorThreadCount == 0) {
acceptorThreadCount = 1;
}
if (pollerThreadCount <= 0) {
pollerThreadCount = 1;
}
setStopLatch(new CountDownLatch(pollerThreadCount));
initialiseSsl();
selectorPool.open();
}以上就是Catalina的整个初始化过程.紧接着初始化完成以后呢就会执行start()方法了.
6.2 daemon.start()
public void start() {
if (getServer() == null) {
load();
}
if (getServer() == null) {
log.fatal("Cannot start server. Server instance is not configured.");
return;
}
long t1 = System.nanoTime();
try {
getServer().start();
} catch (LifecycleException e) {
log.fatal(sm.getString("catalina.serverStartFail"), e);
try {
getServer().destroy();
} catch (LifecycleException e1) {
log.debug("destroy() failed for failed Server ", e1);
}
return;
}
long t2 = System.nanoTime();
if(log.isInfoEnabled()) {
log.info("Server startup in " + ((t2 - t1) / 1000000) + " ms");
}
if (useShutdownHook) {
if (shutdownHook == null) {
shutdownHook = new CatalinaShutdownHook();
}
Runtime.getRuntime().addShutdownHook(shutdownHook);
LogManager logManager = LogManager.getLogManager();
if (logManager instanceof ClassLoaderLogManager) {
((ClassLoaderLogManager) logManager).setUseShutdownHook(
false);
}
}
if (await) {
await();
stop();
}
}如上代码所示核心代码就是getServer().start(); 接下来我们看看server.start()做了什么
protected void startInternal() throws LifecycleException {
fireLifecycleEvent(CONFIGURE_START_EVENT, null);
setState(LifecycleState.STARTING);
globalNamingResources.start();
synchronized (servicesLock) {
for (Service service : services) {
service.start();
}
}
}Server.start()会启动所有的service,那么service做了什么呢我们来看看.
protected void startInternal() throws LifecycleException {
if(log.isInfoEnabled()) {
log.info(sm.getString("standardService.start.name", this.name));
}
setState(LifecycleState.STARTING);
if (engine != null) {
synchronized (engine) {
engine.start();
}
}
synchronized (executors) {
for (Executor executor: executors) {
executor.start();
}
}
mapperListener.start();
synchronized (connectorsLock) {
for (Connector connector: connectors) {
try {
if (connector.getState() != LifecycleState.FAILED) {
connector.start();
}
} catch (Exception e) {
log.error(sm.getString(
"standardService.connector.startFailed",
connector), e);
}
}
}
}如上代码片段所示,可以看到service.start()主要就是调用了engin.start(),executor.start(),connector.start()那么这三个start()分别做了什么呢.我们先看一下engin.start()做了什么?
protected synchronized void startInternal() throws LifecycleException {
if (log.isInfoEnabled()) {
log.info(sm.getString("standardEngine.start", ServerInfo.getServerInfo()));
}
super.startInternal();
}如上代码所示engin.start()调用了父类的 ContainerBase的startInternal()
public abstract class ContainerBase extends LifecycleMBeanBase implements Container {
protected synchronized void startInternal() throws LifecycleException {
logger = null;
getLogger();
Cluster cluster = getClusterInternal();
if (cluster instanceof Lifecycle) {
((Lifecycle) cluster).start();
}
Realm realm = getRealmInternal();
if (realm instanceof Lifecycle) {
((Lifecycle) realm).start();
}
Container children[] = findChildren();
List<Future<Void>> results = new ArrayList<>();
for (Container child : children) {
results.add(startStopExecutor.submit(new StartChild(child)));
}
MultiThrowable multiThrowable = null;
for (Future<Void> result : results) {
try {
result.get();
} catch (Throwable e) {
log.error(sm.getString("containerBase.threadedStartFailed"), e);
if (multiThrowable == null) {
multiThrowable = new MultiThrowable();
}
multiThrowable.add(e);
}
}
if (multiThrowable != null) {
throw new LifecycleException(sm.getString("containerBase.threadedStartFailed"),
multiThrowable.getThrowable());
}
if (pipeline instanceof Lifecycle) {
((Lifecycle) pipeline).start();
}
setState(LifecycleState.STARTING);
threadStart();
}
}
}如上代码片端所示,核心代码如
for (Container child : children) {
results.add(startStopExecutor.submit(new StartChild(child)));
}可以看到提交线程,启动所有的StartChild类,这个时候也许就比较关心了,这些线程分别对自容器做了什么,看到StartChild内部
private static class StartChild implements Callable<Void> {
private Container child;
public StartChild(Container child) {
this.child = child;
}
@Override
public Void call() throws LifecycleException {
child.start();
return null;
}
}实际上是每个线程分别启动了子容器.那么Engin的自容器主要是Host可以知道的是自此的话就会带动一个Host上的所有Context进行启动,然后就是相应的Wapper等的容器的启动了.所以Engin.start()方法就是递归的启动所有的子容器.
.这里我们来看看executor.start()做了什么.可以看到tomcat内部自定义了线程池和队列.那么这个线程池和队列主要做了什么呢,其实在启动线程worker线程的时候主要就是启动了核心线程.
protected void startInternal() throws LifecycleException {
taskqueue = new TaskQueue(maxQueueSize);
TaskThreadFactory tf = new TaskThreadFactory(namePrefix,daemon,getThreadPriority());
executor = new ThreadPoolExecutor(getMinSpareThreads(), getMaxThreads(), maxIdleTime, TimeUnit.MILLISECONDS,taskqueue, tf);
executor.setThreadRenewalDelay(threadRenewalDelay);
if (prestartminSpareThreads) {
executor.prestartAllCoreThreads();
}
taskqueue.setParent(executor);
setState(LifecycleState.STARTING);
}connector.start() 接下来就是connector的start() 方法了.
protected void startInternal() throws LifecycleException {
if (getPort() < 0) {
throw new LifecycleException(sm.getString(
"coyoteConnector.invalidPort", Integer.valueOf(getPort())));
}
setState(LifecycleState.STARTING);
try { //Http11NioProtocol
protocolHandler.start();
} catch (Exception e) {
throw new LifecycleException(
sm.getString("coyoteConnector.protocolHandlerStartFailed"), e);
}
}如上所示核心代码又回到了 protocolHandler.start() 这个方法.
public void start() throws Exception {
if (getLog().isInfoEnabled()) {
getLog().info(sm.getString("abstractProtocolHandler.start", getName()));
}
endpoint.start();
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();
}endpoint.start(); 这个代码是重点.
public final void start() throws Exception {
if (bindState == BindState.UNBOUND) {
bind();
bindState = BindState.BOUND_ON_START;
}
startInternal();
}如上图所示就是start()方法做的事情.这里我们主要看到的是startInternal();
public void startInternal() throws Exception {
if (!running) {
running = true;
paused = false;
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();
}
initializeConnectionLatch();
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();
}
startAcceptorThreads();
}
}如上所示就是tomcat启动的核型流程,其中有三个核心代码 startAcceptorThreads();/pollerThread.start();/ createExecutor(); 这里就是我们工作模型里面体现出来的 Poller/Acceptor/worker的工作模型了.那么我们现在来看看这三个主要角色分别做了什么.
protected final void startAcceptorThreads() {
int count = getAcceptorThreadCount();
acceptors = new Acceptor[count];
for (int i = 0; i < count; i++) {
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();
}
}可以分别看到acceptor/poller都分别是一个线程的runnable实现类.
protected class Acceptor extends AbstractEndpoint.Acceptor {
public void run() {
int errorDelay = 0;
while (running) {
while (paused && running) {
state = AcceptorState.PAUSED;
try {
Thread.sleep(50);
} catch (InterruptedException e) {
// Ignore
}
}
if (!running) {
break;
}
state = AcceptorState.RUNNING;
try {
countUpOrAwaitConnection();
SocketChannel socket = null;
try {
socket = serverSock.accept();
} catch (IOException ioe) {
countDownConnection();
if (running) {
errorDelay = handleExceptionWithDelay(errorDelay);
throw ioe;
} else {
break;
}
}
errorDelay = 0;
if (running && !paused) {
if (!setSocketOptions(socket)) {
closeSocket(socket);
}
} else {
closeSocket(socket);
}
} catch (Throwable t) {
ExceptionUtils.handleThrowable(t);
log.error(sm.getString("endpoint.accept.fail"), t);
}
}
state = AcceptorState.ENDED;
}如上代码片段所示我们可以看到其实是对 setSocketOptions(socket)这个方法进行了调用.那么这个方法做了什么呢?
protected boolean setSocketOptions(SocketChannel socket) {
try {
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());
if (isSSLEnabled()) {
channel = new SecureNioChannel(socket, bufhandler, selectorPool, this);
} else {
channel = new NioChannel(socket, bufhandler);
}
} else {
channel.setIOChannel(socket);
channel.reset();
}
getPoller0().register(channel);
} catch (Throwable t) {
ExceptionUtils.handleThrowable(t);
try {
log.error("",t);
} catch (Throwable tt) {
ExceptionUtils.handleThrowable(tt);
}
return false;
}
return true;
}如上代码片段所示其实核型代码就是获取到poller线程对象把,socket包裹起来的channel对象 注册都poller线程对象中,好了acceptor的任务就是接请求,并把请求注册到poller中getPoller0().register(channel);好了那么我们来看看poller线程做了什么?
public class Poller implements Runnable {
private final SynchronizedQueue<PollerEvent> events =
new SynchronizedQueue<>();
public void run() {
while (true) {
boolean hasEvents = false;
try {
if (!close) {
hasEvents = events();
if (wakeupCounter.getAndSet(-1) > 0) {
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) {
ExceptionUtils.handleThrowable(x);
log.error("",x);
continue;
}
if (keyCount == 0) {
hasEvents = (hasEvents | events());
}
Iterator<SelectionKey> iterator =
keyCount > 0 ? selector.selectedKeys().iterator() : null;
while (iterator != null && iterator.hasNext()) {
SelectionKey sk = iterator.next();
iterator.remove();
NioSocketWrapper socketWrapper = (NioSocketWrapper) sk.attachment();
if (socketWrapper != null) {
processKey(sk, socketWrapper);
}
}
timeout(keyCount,hasEvents);
}
getStopLatch().countDown();}}如上代码所示就是poller的代码,那么核心代码是什么呢?processKey(sk, socketWrapper).poller主要就是通过acceptor注册进来的事情,进行处理核心方法就如上面代码所示.
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()) {
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);
} catch (Throwable t) {
ExceptionUtils.handleThrowable(t);
log.error("",t);
}
}
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;
}sc = createSocketProcessor(socketWrapper, event);/ executor.execute(sc);核心代码如上把socket连接包装成processor对象然后通过线程池去对processor做一个多线程的处理.那么processor做了什么呢?
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 {
int handshake = -1;
try {
if (key != null) {
if (socket.isHandshakeComplete()) {
handshake = 0;
} else if (event == SocketEvent.STOP || event == SocketEvent.DISCONNECT ||
event == SocketEvent.ERROR) {
handshake = -1;
} else {
handshake = socket.handshake(key.isReadable(), key.isWritable());
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;
if (event == null) {
state = getHandler().process(socketWrapper, SocketEvent.OPEN_READ);
} else {
state = getHandler().process(socketWrapper, event);
}
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){
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("", t);
socket.getPoller().cancelledKey(key);
} finally {
socketWrapper = null;
event = null;
if (running && !paused) {
processorCache.push(this);
}
}
}
}如上代码所示,虽然代码有点长,不过核心代码 getHandler().process(socketWrapper, event);我们可以跟进去看看做了什么.
public SocketState process(SocketWrapperBase<S> wrapper, SocketEvent
...../省略部分代码/
do {
state = processor.process(wrapper, status);
if (state == SocketState.UPGRADING) {
UpgradeToken upgradeToken = processor.getUpgradeToken();
ByteBuffer leftOverInput = processor.getLeftoverInput();
wrapper.unRead(leftOverInput);
if (upgradeToken == null) {
UpgradeProtocol upgradeProtocol = getProtocol().getUpgradeProtocol("h2c");
if (upgradeProtocol != null) {
release(processor);
processor = upgradeProtocol.getProcessor(wrapper, getProtocol().getAdapter());
connections.put(socket, processor);
} else {
if (getLog().isDebugEnabled()) {
getLog().debug(sm.getString(
"abstractConnectionHandler.negotiatedProcessor.fail",
"h2c"));
}
state = SocketState.CLOSED;
}
} else {
HttpUpgradeHandler httpUpgradeHandler = upgradeToken.getHttpUpgradeHandler();
release(processor);
processor = getProtocol().createUpgradeProcessor(wrapper, upgradeToken);
if (getLog().isDebugEnabled()) {
getLog().debug(sm.getString("abstractConnectionHandler.upgradeCreate",
processor, wrapper));
}
connections.put(socket, processor);
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);
...../省略部分代码/
}如上代码片段所示核心代码state = processor.process(wrapper, status);
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();
if (getLog().isDebugEnabled()) {
getLog().debug("Processing dispatch type: [" + nextDispatch + "]");
}
state = dispatch(nextDispatch.getSocketStatus());
if (!dispatches.hasNext()) {
state = checkForPipelinedData(state, socketWrapper);
}
} 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);
state = checkForPipelinedData(state, socketWrapper);
} else if (status == SocketEvent.OPEN_WRITE) {
// Extra write event likely after async, ignore
state = SocketState.LONG;
} else if (status == SocketEvent.OPEN_READ) {
//核心代码
state = service(socketWrapper);
} else if (status == SocketEvent.CONNECT_FAIL) {
logAccess(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;
}
....../*省略部分代码*/
} while (state == SocketState.ASYNC_END ||
dispatches != null && state != SocketState.CLOSED);
return state;
}核心代码 state = service(socketWrapper);
public SocketState service(SocketWrapperBase<?> socketWrapper)
throws IOException {
getAdapter().service(request, response);
}终于看到实际上是通过adaper适配器去完成后面的请求处理到我们的容器处理流程的,结下来就是我们的worker工作流程了.service(org.apache.coyote.Request req, org.apache.coyote.Response res),当我们把请求对象和相应对象交给 CoyoteAdapter对象以后那我们就说我们的tomcat启动流程已经结束了.接下来就是请求对象到容器的流转过程与业务代码过程.我们看下一节的工作流程图.
七 tomcat容器和数据传输流程
如上图所示是容器数据的输入流程讲解,可以看到tomcat中当请求线程处理模型完成以后呢,调用就可以通过 CoyoteAdapter这个类来进行数据的传输了.整个传输过程无非就是从Engin->Host->Context->Wapper->Filter->GenericServlet->Httpservlet的过程.这里可以看到tomcat给其他web代码框架留的入口就是Httpservlet的service()方法.所以只要你时候了tomcat服务中间件启动服务接收来自上层的http请求,最终数据都会流到这里.只要你重写service方法就可以拿到请求数据了.下面我们来看看源代码. CoyoteAdapter 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) {
request = connector.createRequest();
request.setCoyoteRequest(req);
response = connector.createResponse();
response.setCoyoteResponse(res);
request.setResponse(response);
response.setRequest(request);
req.setNote(ADAPTER_NOTES, request);
res.setNote(ADAPTER_NOTES, response);
req.getParameters().setQueryStringCharset(connector.getURICharset());
}
if (connector.getXpoweredBy()) {
response.addHeader("X-Powered-By", POWERED_BY);
}
boolean async = false;
boolean postParseSuccess = false;
req.getRequestProcessor().setWorkerThreadName(THREAD_NAME.get());
try {
postParseSuccess = postParseRequest(req, request, res, response);
if (postParseSuccess) {
request.setAsyncSupported(
connector.getService().getContainer().getPipeline().isAsyncSupported());
connector.getService().getContainer().getPipeline().getFirst().invoke(
request, response);
}
if (request.isAsync()) {
async = true;
ReadListener readListener = req.getReadListener();
if (readListener != null && request.isFinished()) {
ClassLoader oldCL = null;
try {
oldCL = request.getContext().bind(false, null);
if (req.sendAllDataReadEvent()) {
req.getReadListener().onAllDataRead();
}
} finally {
request.getContext().unbind(false, oldCL);
}
}
Throwable throwable =
(Throwable) request.getAttribute(RequestDispatcher.ERROR_EXCEPTION);
// If an async request was started, is not going to end once
// this container thread finishes and an error occurred, trigger
// the async error process
if (!request.isAsyncCompleting() && throwable != null) {
request.getAsyncContextInternal().setErrorState(throwable, true);
}
} else {
request.finishRequest();
response.finishResponse();
}
} catch (IOException e) {
// Ignore
} finally {
AtomicBoolean error = new AtomicBoolean(false);
res.action(ActionCode.IS_ERROR, error);
if (request.isAsyncCompleting() && error.get()) {
res.action(ActionCode.ASYNC_POST_PROCESS, null);
async = false;
}
if (!async && postParseSuccess) {
Context context = request.getContext();
Host host = request.getHost();
long time = System.currentTimeMillis() - req.getStartTime();
if (context != null) {
context.logAccess(request, response, time, false);
} else if (response.isError()) {
if (host != null) {
host.logAccess(request, response, time, false);
} else {
connector.getService().getContainer().logAccess(
request, response, time, false);
}
}
}
req.getRequestProcessor().setWorkerThreadName(null);
if (!async) {
updateWrapperErrorCount(request, response);
request.recycle();
response.recycle();
}
}
}核心代码如上connector.getService().getContainer().getPipeline().getFirst().invoke(request, response);这里可以看到调用的service的container的invoke()方法,好的我们跟进去 StandardEngineValve.
final class StandardEngineValve extends ValveBase {
public StandardEngineValve() {
super(true);
}
@Override
public final void invoke(Request request, Response response)
throws IOException, ServletException {
Host host = request.getHost();
if (host == null) {
if (!response.isError()) {
response.sendError(404);
}
return;
}
if (request.isAsyncSupported()) {
request.setAsyncSupported(host.getPipeline().isAsyncSupported());
}
host.getPipeline().getFirst().invoke(request, response);
}
}如上代码核心片段request/response对象继续下沉host.getPipeline().getFirst().invoke(request, response);这里可以看到是取的host的第一个Value值好的我们接着向下进行
final class StandardHostValve extends ValveBase {
@Override
public final void invoke(Request request, Response response)
throws IOException, ServletException {
Context context = request.getContext();
if (context == null) {
if (!response.isError()) {
response.sendError(404);
}
return;
}
if (request.isAsyncSupported()) {
request.setAsyncSupported(context.getPipeline().isAsyncSupported());
}
boolean asyncAtStart = request.isAsync();
try {
context.bind(Globals.IS_SECURITY_ENABLED, MY_CLASSLOADER);
if (!asyncAtStart && !context.fireRequestInitEvent(request.getRequest())) {
return;
}
try {
if (!response.isErrorReportRequired()) {
context.getPipeline().getFirst().invoke(request, response);
}
} catch (Throwable t) {
ExceptionUtils.handleThrowable(t);
container.getLogger().error("Exception Processing " + request.getRequestURI(), t);
if (!response.isErrorReportRequired()) {
request.setAttribute(RequestDispatcher.ERROR_EXCEPTION, t);
throwable(request, response, t);
}
}
response.setSuspended(false);
Throwable t = (Throwable) request.getAttribute(RequestDispatcher.ERROR_EXCEPTION);
if (!context.getState().isAvailable()) {
return;
}
if (response.isErrorReportRequired()) {
AtomicBoolean result = new AtomicBoolean(false);
response.getCoyoteResponse().action(ActionCode.IS_IO_ALLOWED, result);
if (result.get()) {
if (t != null) {
throwable(request, response, t);
} else {
status(request, response);
}
}
}
if (!request.isAsync() && !asyncAtStart) {
context.fireRequestDestroyEvent(request.getRequest());
}
} finally {
if (ACCESS_SESSION) {
request.getSession(false);
}
context.unbind(Globals.IS_SECURITY_ENABLED, MY_CLASSLOADER);
}
}
}如上所示是host容器的Value的核心代码片段.接下来我们可以看到 context.getPipeline().getFirst().invoke(request, response); 这样一段代码,把请求参数以及上下文对象继续传给我们的context对象.好那么context对象做了什么呢.
final class StandardContextValve extends ValveBase {
private static final StringManager sm = StringManager.getManager(StandardContextValve.class);
public StandardContextValve() {
super(true);
}
*/
@Override
public final void invoke(Request request, Response response)
throws IOException, ServletException {
MessageBytes requestPathMB = request.getRequestPathMB();
if ((requestPathMB.startsWithIgnoreCase("/META-INF/", 0))
|| (requestPathMB.equalsIgnoreCase("/META-INF"))
|| (requestPathMB.startsWithIgnoreCase("/WEB-INF/", 0))
|| (requestPathMB.equalsIgnoreCase("/WEB-INF"))) {
response.sendError(HttpServletResponse.SC_NOT_FOUND);
return;
}
Wrapper wrapper = request.getWrapper();
if (wrapper == null || wrapper.isUnavailable()) {
response.sendError(HttpServletResponse.SC_NOT_FOUND);
return;
}
try {
response.sendAcknowledgement(ContinueResponseTiming.IMMEDIATELY);
} catch (IOException ioe) {
container.getLogger().error(sm.getString(
"standardContextValve.acknowledgeException"), ioe);
request.setAttribute(RequestDispatcher.ERROR_EXCEPTION, ioe);
response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
return;
}
if (request.isAsyncSupported()) {
request.setAsyncSupported(wrapper.getPipeline().isAsyncSupported());
}
wrapper.getPipeline().getFirst().invoke(request, response);
}
}这就是我们的context对想的invoke方法.好的接下来我们继续观察 wrapper.getPipeline().getFirst().invoke(request, response);发现了一样的核心代码.我们看看wapper做了什么.
final class StandardWrapperValve extends ValveBase {
private static final StringManager sm = StringManager.getManager(StandardWrapperValve.class);
public StandardWrapperValve() {
super(true);
}
private volatile long processingTime;
private volatile long maxTime;
private volatile long minTime = Long.MAX_VALUE;
private final AtomicInteger requestCount = new AtomicInteger(0);
private final AtomicInteger errorCount = new AtomicInteger(0);
@Override
public final void invoke(Request request, Response response)
throws IOException, ServletException {
boolean unavailable = false;
Throwable throwable = null;
long t1=System.currentTimeMillis();
requestCount.incrementAndGet();
StandardWrapper wrapper = (StandardWrapper) getContainer();
Servlet servlet = null;
Context context = (Context) wrapper.getParent();
if (!context.getState().isAvailable()) {
response.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE,
sm.getString("standardContext.isUnavailable"));
unavailable = true;
}
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;
}
try {
if (!unavailable) {
servlet = wrapper.allocate();
}
} catch (UnavailableException e) {
container.getLogger().error(
sm.getString("standardWrapper.allocateException",
wrapper.getName()), e);
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()));
}
} catch (ServletException e) {
container.getLogger().error(sm.getString("standardWrapper.allocateException",
wrapper.getName()), StandardWrapper.getRootCause(e));
throwable = e;
exception(request, response, e);
} catch (Throwable e) {
ExceptionUtils.handleThrowable(e);
container.getLogger().error(sm.getString("standardWrapper.allocateException",
wrapper.getName()), e);
throwable = e;
exception(request, response, e);
servlet = null;
}
MessageBytes requestPathMB = request.getRequestPathMB();
DispatcherType dispatcherType = DispatcherType.REQUEST;
if (request.getDispatcherType()==DispatcherType.ASYNC) {
dispatcherType = DispatcherType.ASYNC;
}
request.setAttribute(Globals.DISPATCHER_TYPE_ATTR,dispatcherType);
request.setAttribute(Globals.DISPATCHER_REQUEST_PATH_ATTR,
requestPathMB);
ApplicationFilterChain filterChain =
ApplicationFilterFactory.createFilterChain(request, wrapper, servlet);
Container container = this.container;
try {
if ((servlet != null) && (filterChain != null)) {
if (context.getSwallowOutput()) {
try {
SystemLogHandler.startCapture();
if (request.isAsyncDispatching()) {
request.getAsyncContextInternal().doInternalDispatch();
} else {
filterChain.doFilter(request.getRequest(),
response.getResponse());
}
} finally {
String log = SystemLogHandler.stopCapture();
if (log != null && log.length() > 0) {
context.getLogger().info(log);
}
}
} else {
if (request.isAsyncDispatching()) {
request.getAsyncContextInternal().doInternalDispatch();
} else {
filterChain.doFilter
(request.getRequest(), response.getResponse());
}
}
}
} catch (ClientAbortException | CloseNowException e) {
if (container.getLogger().isDebugEnabled()) {
container.getLogger().debug(sm.getString(
"standardWrapper.serviceException", wrapper.getName(),
context.getName()), e);
}
throwable = e;
exception(request, response, e);
} 我们知道wapper包裹的就是servlet.那么我们看看wapper的核心代码是什么,可以看到wapper
定义了一个 ApplicationFilterChain的调用链,然后调用了filterChain.doFilter(request.getRequest(),response.getResponse());这个方法,除此之外呢我们还可以看到另一个方法 wrapper.deallocate(servlet);这里其实是非wapper分配了对应的servlet对象那么我们接下来往下看一下, filterChain.doFilter(request.getRequest(),response.getResponse());
public final class ApplicationFilterChain implements FilterChain{
public void doFilter(ServletRequest request, ServletResponse response)
throws IOException, ServletException {
if( Globals.IS_SECURITY_ENABLED ) {
final ServletRequest req = request;
final ServletResponse res = response;
try {
java.security.AccessController.doPrivileged(
new java.security.PrivilegedExceptionAction<Void>() {
@Override
public Void run()
throws ServletException, IOException {
internalDoFilter(req,res);
return null;
}
}
);
} catch( PrivilegedActionException pe) {
Exception e = pe.getException();
if (e instanceof ServletException) {
throw (ServletException) e;
} else if (e instanceof IOException) {
throw (IOException) e;
} else if (e instanceof RuntimeException) {
throw (RuntimeException) e;
} else {
throw new ServletException(e.getMessage(), e);
}
}
} else {
internalDoFilter(request,response);
}
}如上所示主要是调用了 internalDoFilter(request,response);这个方法,好了那么我们进行看看这里面是掉用的什么东西.
public final class ApplicationFilterChain implements FilterChain{
private void internalDoFilter(ServletRequest request,
ServletResponse response)
throws IOException, ServletException {
if (pos < n) {
ApplicationFilterConfig filterConfig = filters[pos++];
try {
Filter filter = filterConfig.getFilter();
if (request.isAsyncSupported() && "false".equalsIgnoreCase(
filterConfig.getFilterDef().getAsyncSupported())) {
request.setAttribute(Globals.ASYNC_SUPPORTED_ATTR, Boolean.FALSE);
}
if( Globals.IS_SECURITY_ENABLED ) {
final ServletRequest req = request;
final ServletResponse res = response;
Principal principal =
((HttpServletRequest) req).getUserPrincipal();
Object[] args = new Object[]{req, res, this};
SecurityUtil.doAsPrivilege ("doFilter", filter, classType, args, principal);
} else {
filter.doFilter(request, response, this);
}
} catch (IOException | ServletException | RuntimeException e) {
throw e;
} catch (Throwable e) {
e = ExceptionUtils.unwrapInvocationTargetException(e);
ExceptionUtils.handleThrowable(e);
throw new ServletException(sm.getString("filterChain.filter"), e);
}
return;
}
try {
if (ApplicationDispatcher.WRAP_SAME_OBJECT) {
lastServicedRequest.set(request);
lastServicedResponse.set(response);
}
if (request.isAsyncSupported() && !servletSupportsAsync) {
request.setAttribute(Globals.ASYNC_SUPPORTED_ATTR,
Boolean.FALSE);
}
if ((request instanceof HttpServletRequest) &&
(response instanceof HttpServletResponse) &&
Globals.IS_SECURITY_ENABLED ) {
final ServletRequest req = request;
final ServletResponse res = response;
Principal principal =
((HttpServletRequest) req).getUserPrincipal();
Object[] args = new Object[]{req, res};
SecurityUtil.doAsPrivilege("service",
servlet,
classTypeUsedInService,
args,
principal);
} else {
servlet.service(request, response);
}
} catch (IOException | ServletException | RuntimeException e) {
throw e;
} catch (Throwable e) {
e = ExceptionUtils.unwrapInvocationTargetException(e);
ExceptionUtils.handleThrowable(e);
throw new ServletException(sm.getString("filterChain.servlet"), e);
} finally {
if (ApplicationDispatcher.WRAP_SAME_OBJECT) {
lastServicedRequest.set(null);
lastServicedResponse.set(null);
}
}
}如上代码核心代码如下 filter.doFilter(request, response, this);/servlet.service(request, response);终于我们看到了熟悉的东西,一个是filter,一个是servlet.到了我们熟悉的servlet以后,那么我们来看看servlet主要是做了什么事情呢.这里主要看的是抽象类 GenericServlet 可以看到这个类中. service(ServletRequest req, ServletResponse res)这个抽象的方法.接下来我
public abstract class GenericServlet implements Servlet, ServletConfig,
java.io.Serializable {
private static final long serialVersionUID = 1L;
private transient ServletConfig config;
public GenericServlet() {}
@Override
public void destroy() {
}
@Override
public ServletConfig getServletConfig() {
return config;
}
@Override
public ServletContext getServletContext() {
return getServletConfig().getServletContext();
}
@Override
public abstract void service(ServletRequest req, ServletResponse res)
throws ServletException, IOException;
}们看看这个类的实现类主要做了什么,
public abstract class HttpServlet extends GenericServlet {
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
String method = req.getMethod();
if (method.equals(METHOD_GET)) {
long lastModified = getLastModified(req);
if (lastModified == -1) {
doGet(req, resp);
} else {
long ifModifiedSince;
try {
ifModifiedSince = req.getDateHeader(HEADER_IFMODSINCE);
} catch (IllegalArgumentException iae) {
ifModifiedSince = -1;
}
if (ifModifiedSince < (lastModified / 1000 * 1000)) {
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 {
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);
}
}
private void maybeSetLastModified(HttpServletResponse resp,long lastModified) {
if (resp.containsHeader(HEADER_LASTMOD)) { return;}
if (lastModified >= 0) {
resp.setDateHeader(HEADER_LASTMOD, lastModified);
}
}
@Override
public void service(ServletRequest req, ServletResponse res)
throws ServletException, IOException {
HttpServletRequest request;
HttpServletResponse response;
try {
request = (HttpServletRequest) req;
response = (HttpServletResponse) res;
} catch (ClassCastException e) {
throw new ServletException(lStrings.getString("http.non_http"));
}
service(request, response);
}
}如上图所示就是 GenericServlet 类的实现类了,看到这里我们就很熟悉了,最初我们用tomcat启动的web项目就是配置servelet的,然而这些个servlert就是重写了httpservlet的doxxx()方法的.随着技术的演进和发展,我们发现技术又革新了,引入了springmvc框架以后,对service()方法进行了重写.最终我们实现了tomcat和spring的整合.
本文章为转载内容，我们尊重原作者对文章享有的著作权。如有内容错误或侵权问题，欢迎原作者联系我们进行内容更正或删除文章。
