tomcat 启动类
我们通过tomcat的catalina.sh 的脚本启动tomcat时，执行的是tomcat的Bootstrap类的main方法。这是tomcat的入口。
代码如下：
public static void main(String args[]) {
synchronized (daemonLock) {
if (daemon == null) {
// Don't set daemon until init() has completed
Bootstrap bootstrap = new Bootstrap();
try {
bootstrap.init();
} catch (Throwable t) {
handleThrowable(t);
t.printStackTrace();
return;
}
daemon = bootstrap;
} else {
// When running as a service the call to stop will be on a new
// thread so make sure the correct class loader is used to
// prevent a range of class not found exceptions.
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);
}
}
tomcat的启动需要先执行Bootstrap的初始化init()后，再执行load，start核心方法，我们下线一次分析这个这三个方法
初始化Catalina
代码如下：
public void init() throws Exception {
initClassLoaders();
Thread.currentThread().setContextClassLoader(catalinaLoader);
SecurityClassLoad.securityClassLoad(catalinaLoader);
// Load our startup class and call its process() method
if (log.isDebugEnabled())
log.debug("Loading startup class");
Class<?> startupClass = catalinaLoader.loadClass("org.apache.catalina.startup.Catalina");
Object startupInstance = startupClass.getConstructor().newInstance();
// Set the shared extensions class loader
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;
}
主要是创建common-classloader，serverClassLoader都是用这个类，同时用common-classloader加载Catalina这个类，致于为啥要用classloader来加载这个类，个人觉得是安全，因为这个common-classloader只会加载jdk以及tomcat自己lib目录下的jar包，而不会加载其他目录下的jar。
Load 部分分析
load方法tomcat也是通过反射调用的Catalina 的load()方法，这里就开始解析tomcat的核心配置文件server.xml的地方
public void load() {
if (loaded) {
return;
}
loaded = true;
long t1 = System.nanoTime();
initDirs();
// Before digester - it may be needed
initNaming();
// Set configuration source
ConfigFileLoader.setSource(new CatalinaBaseConfigurationSource(Bootstrap.getCatalinaBaseFile(), getConfigFile()));
File file = configFile();
// Create and execute our Digester
// 解析server.xml配置文件
Digester digester = createStartDigester();
try (ConfigurationSource.Resource resource = ConfigFileLoader.getSource().getServerXml()) {
InputStream inputStream = resource.getInputStream();
InputSource inputSource = new InputSource(resource.getURI().toURL().toString());
inputSource.setByteStream(inputStream);
digester.push(this);
digester.parse(inputSource);
} catch (Exception e) {
log.warn(sm.getString("catalina.configFail", file.getAbsolutePath()), e);
if (file.exists() && !file.canRead()) {
log.warn(sm.getString("catalina.incorrectPermissions"));
}
return;
}
getServer().setCatalina(this);
getServer().setCatalinaHome(Bootstrap.getCatalinaHomeFile());
getServer().setCatalinaBase(Bootstrap.getCatalinaBaseFile());
// Stream redirection
initStreams();
// Start the new server
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(sm.getString("catalina.initError"), e);
}
}
long t2 = System.nanoTime();
if(log.isInfoEnabled()) {
log.info(sm.getString("catalina.init", Long.valueOf((t2 - t1) / 1000000)));
}
}
tomcat通过Digester来解析server.xml配置文件，并创建sever对应的StandardServer,service对应的是StandardService，在初始化server时，会把service全部初始化完，包含engin，Connector等。
这里主要说下connector，tomcat默认的connector是http1.1
public Connector(String protocol) {
boolean aprConnector = AprLifecycleListener.isAprAvailable() &&
AprLifecycleListener.getUseAprConnector();
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);
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"));
}
Start
tomcat 初始化完后，就开始启动tomcat的nio线程，catalina的工作线程。
/**
* Start a new server instance.
*/
public void start() {
if (getServer() == null) {
load();
}
if (getServer() == null) {
log.fatal(sm.getString("catalina.noServer"));
return;
}
long t1 = System.nanoTime();
// Start the new server
try {
//开始启动服务,是server.xml文件配置的server,执行的是
//StandardServer的startInternal()方法。
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(sm.getString("catalina.startup", Long.valueOf((t2 - t1) / 1000000)));
}
// Register shutdown hook
if (useShutdownHook) {
if (shutdownHook == null) {
shutdownHook = new CatalinaShutdownHook();
}
Runtime.getRuntime().addShutdownHook(shutdownHook);
// If JULI is being used, disable JULI's shutdown hook since
// shutdown hooks run in parallel and log messages may be lost
// if JULI's hook completes before the CatalinaShutdownHook()
LogManager logManager = LogManager.getLogManager();
if (logManager instanceof ClassLoaderLogManager) {
((ClassLoaderLogManager) logManager).setUseShutdownHook(
false);
}
}
if (await) {
await();
stop();
}
}
StandardServer的startInternal 方法如下：
// Start our defined Services
synchronized (servicesLock) {
for (int i = 0; i < services.length; i++) {
//services是server.xml配置文件里的service，实现是StandardService，同理也是执行的startInternal()方法。
services[i].start();
}
}
StandardService的startInternal 是核心，catalina的引擎engin，nio线程都在这里启动
@Override
protected void startInternal() throws LifecycleException {
if(log.isInfoEnabled())
log.info(sm.getString("standardService.start.name", this.name));
setState(LifecycleState.STARTING);
// Start our defined Container first
if (engine != null) {
synchronized (engine) {
//
engine.start();
}
}
//catalina worker 线程池创建，Executor 是由StandardThreadExecutor实现的，具体也是由StandardThreadExecutor的startInternal方法实现。
synchronized (executors) {
for (Executor executor: executors) {
executor.start();
}
}
//这里是tomcat context path路由相关的，后面单独一偏分析
mapperListener.start();
// Start our defined Connectors second
// 初始化nio select和poll线程
synchronized (connectorsLock) {
for (Connector connector: connectors) {
// If it has already failed, don't try and start it
if (connector.getState() != LifecycleState.FAILED) {
connector.start();
}
}
}
}
tomcat工作线程池创建由StandardThreadExecutor的startInternal方法实现，具体实现如下：
protected void startInternal() throws LifecycleException {
//TaskQueue是tomcat的LinkedBlockingQueue，重写了offer等方法
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);
}
tomcat的nio线程创建和启动connector负责实现，后面单独开一偏。
网友评论