tomcat-整启动流程-源码解析
Tomcat整体启动流程
上文了解了大致tomat的相关架构，那么本文是针对tomcat的启动流程进行了解，。tomcat是通过Bootstrap的main方法进行启动，然后通过catalina对象中创建server.xml的解析器，一步到位创建出大部分组件，通过责任链模式进行层层管理。细节可以跟着调试代码关注如下。
源码位置：https://gitee.com/hong99/source-code-learning.git
tomcat整体架构
tomcat的核心启动入口（所有的启动入口）
代码位置
注意：bootstrap调用顺序main->init->load
org.apache.catalina.startup.Bootstrap#main
/**
* Main method and entry point when starting Tomcat via the provided
* scripts.
*
* @param args Command line arguments to be processed
* tomcat 核心启动类 主线程类
*/
public static void main(String args[]) {
//线程同步方式启动
synchronized (daemonLock) {
if (daemon == null) {
//创建 自身
Bootstrap bootstrap = new Bootstrap();
try {
//创建 tomcat自身的初始化
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 {
//默认为启动 标识
String command = "start";
//如果args长度大于0
if (args.length > 0) {
//重新赋值
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")) {
//线程等待，否则tomcat直接就关闭了;就类似于守护线程
daemon.setAwait(true);
//加载
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);
}
}main执行中，第一步初始化就是init，通过这个init进行初始化所有下级;
org.apache.catalina.startup.Bootstrap#init()
/**
* bootstartp 初始化方法
* Initialize daemon.
* @throws Exception Fatal initialization error
*/
public void init() throws Exception {
//初始化类加载器 其中包含 catalinaLoader和sharedLoader
initClassLoaders();
//将catalinaLoader 放到当前线上下文中
Thread.currentThread().setContextClassLoader(catalinaLoader);
//将catalinaLoader 加载到权限管理中
SecurityClassLoad.securityClassLoad(catalinaLoader);
// 是否打印日志开关
if (log.isDebugEnabled()) {
log.debug("Loading startup class");
}
//通过反射方式调用 catalina方法
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");
}
//方法名称为：setParentClassLoader
String methodName = "setParentClassLoader";
Class<?> paramTypes[] = new Class[1];
paramTypes[0] = Class.forName("java.lang.ClassLoader");
Object paramValues[] = new Object[1];
//类加载器
paramValues[0] = sharedLoader;
Method method =
startupInstance.getClass().getMethod(methodName, paramTypes);
//通过反射方式调用
method.invoke(startupInstance, paramValues);
//将这个对象赋值到 catalinaDaemon
catalinaDaemon = startupInstance;
}org.apache.catalina.startup.Bootstrap#load
private void load(String[] arguments) throws Exception {
// Call the load() method 加载的方法名称为load
String methodName = "load";
Object param[];
Class<?> paramTypes[];
//当arguments为空或长度为0时将paramTypes和param 赋为空。
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;
}
//通过 server.xml获取org.apache.catalina.startup.Catalina里面的方法为load
Method method =
catalinaDaemon.getClass().getMethod(methodName, paramTypes);
if (log.isDebugEnabled()) {
log.debug("Calling startup class " + method);
}
//通过反射调用 catalina里面的load无参方法
method.invoke(catalinaDaemon, param);
}到这里就跳出去调catalina的无参load方法。
那么Catalina的调用顺序是：load()->createStartDigester()->getServer().init()
主要的目的是加载sever.xml然后去初始化server，这里注意所有的加载都是通过责任链进行管理，所以getServer都是通过org.apache.catalina.util.LifecycleBase#init进行加载;
org.apache.catalina.startup.Catalina#load()
public void load() {
//如果为false则直接返回
if (loaded) {
return;
}
loaded = true;
long t1 = System.nanoTime();
//空方法 该方式不做其他操作
initDirs();
// Before digester - it may be needed
initNaming();
// Create and execute our Digester
Digester digester = createStartDigester();
InputSource inputSource = null;
InputStream inputStream = null;
File file = null;
//以下是通过流的方式进行加载，然后解析
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);
}
}
}
// This should be included in catalina.jar
// Alternative: don't bother with xml, just create it manually.
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);
//最终在这里进行解析;
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 {
//关闭流
inputStream.close();
} catch (IOException e) {
// Ignore
}
}
}
//进行双向绑定 绑定到server中，而catalina也可以获取到server。
getServer().setCatalina(this);
getServer().setCatalinaHome(Bootstrap.getCatalinaHomeFile());
getServer().setCatalinaBase(Bootstrap.getCatalinaBaseFile());
// Stream redirection
initStreams();
// Start the new server
try {
//启动服务 这些是通过责任链进行管理 进行初始化操作
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");
}
}org.apache.catalina.startup.Catalina#createStartDigester
protected Digester createStartDigester() {
long t1=System.currentTimeMillis();
// Initialize the digester 初始化解析器
Digester digester = new Digester();
//解析器标志为false
digester.setValidating(false);
//执行标记为成
digester.setRulesValidation(true);
//用于存放对象信息 其中包含 类名 来源 端口编移配置
Map<Class<?>, List<String>> fakeAttributes = new HashMap<>();
// Ignore className on all elements
List<String> objectAttrs = new ArrayList<>();
objectAttrs.add("className");
fakeAttributes.put(Object.class, objectAttrs);
// Ignore attribute added by Eclipse for its internal tracking
List<String> contextAttrs = new ArrayList<>();
contextAttrs.add("source");
fakeAttributes.put(StandardContext.class, contextAttrs);
// Ignore Connector attribute used internally but set on Server
List<String> connectorAttrs = new ArrayList<>();
connectorAttrs.add("portOffset");
fakeAttributes.put(Connector.class, connectorAttrs);
digester.setFakeAttributes(fakeAttributes);
digester.setUseContextClassLoader(true);
// Configure the actions we will be using
//以下这些都是在xml的类型
digester.addObjectCreate("Server",
"org.apache.catalina.core.StandardServer",
"className");
digester.addSetProperties("Server");
digester.addSetNext("Server",
"setServer",
"org.apache.catalina.Server");
digester.addObjectCreate("Server/GlobalNamingResources",
"org.apache.catalina.deploy.NamingResourcesImpl");
digester.addSetProperties("Server/GlobalNamingResources");
digester.addSetNext("Server/GlobalNamingResources",
"setGlobalNamingResources",
"org.apache.catalina.deploy.NamingResourcesImpl");
digester.addObjectCreate("Server/Listener",
null, // MUST be specified in the element
"className");
digester.addSetProperties("Server/Listener");
digester.addSetNext("Server/Listener",
"addLifecycleListener",
"org.apache.catalina.LifecycleListener");
digester.addObjectCreate("Server/Service",
"org.apache.catalina.core.StandardService",
"className");
digester.addSetProperties("Server/Service");
digester.addSetNext("Server/Service",
"addService",
"org.apache.catalina.Service");
digester.addObjectCreate("Server/Service/Listener",
null, // MUST be specified in the element
"className");
digester.addSetProperties("Server/Service/Listener");
digester.addSetNext("Server/Service/Listener",
"addLifecycleListener",
"org.apache.catalina.LifecycleListener");
//Executor 该线程池在最新版本中被屏蔽了 可查看server.xml <Connector executor="tomcatThreadPool"
digester.addObjectCreate("Server/Service/Executor",
"org.apache.catalina.core.StandardThreadExecutor",
"className");
digester.addSetProperties("Server/Service/Executor");
digester.addSetNext("Server/Service/Executor",
"addExecutor",
"org.apache.catalina.Executor");
digester.addRule("Server/Service/Connector",
new ConnectorCreateRule());
digester.addRule("Server/Service/Connector",
new SetAllPropertiesRule(new String[]{"executor", "sslImplementationName"}));
digester.addSetNext("Server/Service/Connector",
"addConnector",
"org.apache.catalina.connector.Connector");
digester.addRule("Server/Service/Connector", new AddPortOffsetRule());
digester.addObjectCreate("Server/Service/Connector/SSLHostConfig",
"org.apache.tomcat.util.net.SSLHostConfig");
digester.addSetProperties("Server/Service/Connector/SSLHostConfig");
digester.addSetNext("Server/Service/Connector/SSLHostConfig",
"addSslHostConfig",
"org.apache.tomcat.util.net.SSLHostConfig");
digester.addRule("Server/Service/Connector/SSLHostConfig/Certificate",
new CertificateCreateRule());
digester.addRule("Server/Service/Connector/SSLHostConfig/Certificate",
new SetAllPropertiesRule(new String[]{"type"}));
digester.addSetNext("Server/Service/Connector/SSLHostConfig/Certificate",
"addCertificate",
"org.apache.tomcat.util.net.SSLHostConfigCertificate");
digester.addObjectCreate("Server/Service/Connector/SSLHostConfig/OpenSSLConf",
"org.apache.tomcat.util.net.openssl.OpenSSLConf");
digester.addSetProperties("Server/Service/Connector/SSLHostConfig/OpenSSLConf");
digester.addSetNext("Server/Service/Connector/SSLHostConfig/OpenSSLConf",
"setOpenSslConf",
"org.apache.tomcat.util.net.openssl.OpenSSLConf");
digester.addObjectCreate("Server/Service/Connector/SSLHostConfig/OpenSSLConf/OpenSSLConfCmd",
"org.apache.tomcat.util.net.openssl.OpenSSLConfCmd");
digester.addSetProperties("Server/Service/Connector/SSLHostConfig/OpenSSLConf/OpenSSLConfCmd");
digester.addSetNext("Server/Service/Connector/SSLHostConfig/OpenSSLConf/OpenSSLConfCmd",
"addCmd",
"org.apache.tomcat.util.net.openssl.OpenSSLConfCmd");
digester.addObjectCreate("Server/Service/Connector/Listener",
null, // MUST be specified in the element
"className");
digester.addSetProperties("Server/Service/Connector/Listener");
digester.addSetNext("Server/Service/Connector/Listener",
"addLifecycleListener",
"org.apache.catalina.LifecycleListener");
digester.addObjectCreate("Server/Service/Connector/UpgradeProtocol",
null, // MUST be specified in the element
"className");
digester.addSetProperties("Server/Service/Connector/UpgradeProtocol");
digester.addSetNext("Server/Service/Connector/UpgradeProtocol",
"addUpgradeProtocol",
"org.apache.coyote.UpgradeProtocol");
// Add RuleSets for nested elements
digester.addRuleSet(new NamingRuleSet("Server/GlobalNamingResources/"));
digester.addRuleSet(new EngineRuleSet("Server/Service/"));
digester.addRuleSet(new HostRuleSet("Server/Service/Engine/"));
digester.addRuleSet(new ContextRuleSet("Server/Service/Engine/Host/"));
addClusterRuleSet(digester, "Server/Service/Engine/Host/Cluster/");
digester.addRuleSet(new NamingRuleSet("Server/Service/Engine/Host/Context/"));
// When the 'engine' is found, set the parentClassLoader.
digester.addRule("Server/Service/Engine",
new SetParentClassLoaderRule(parentClassLoader));
addClusterRuleSet(digester, "Server/Service/Engine/Cluster/");
long t2=System.currentTimeMillis();
if (log.isDebugEnabled()) {
log.debug("Digester for server.xml created " + ( t2-t1 ));
}
return digester;
}org.apache.catalina.util.LifecycleBase#init
通过责任链管理生命周期;
@Override
public final synchronized void init() throws LifecycleException {
if (!state.equals(LifecycleState.NEW)) {
invalidTransition(Lifecycle.BEFORE_INIT_EVENT);
}
try {
//设置生命周期状态
setStateInternal(LifecycleState.INITIALIZING, null, false);
initInternal();
setStateInternal(LifecycleState.INITIALIZED, null, false);
} catch (Throwable t) {
handleSubClassException(t, "lifecycleBase.initFail", toString());
}
}通过以上的initInternal()进入StandardServer#initInternal方法;
这里注意：StandardServer的执行顺序是：initInterna->NamingResourcesImpl#initInternal->service.init();
通过initInterna 为初始化server容器然后通过初始化NamingResourcesImpl#initInternal是JNIDI的数据连接服务，然后再初始多个service
org.apache.catalina.core.StandardServer#initInternal
@Override
protected void initInternal() throws LifecycleException {
super.initInternal();
// Register global String cache
// Note although the cache is global, if there are multiple Servers
// present in the JVM (may happen when embedding) then the same cache
// will be registered under multiple names
onameStringCache = register(new StringCache(), "type=StringCache");
// Register the MBeanFactory
MBeanFactory factory = new MBeanFactory();
factory.setContainer(this);
onameMBeanFactory = register(factory, "type=MBeanFactory");
// Register the naming resources
globalNamingResources.init();
// Populate the extension validator with JARs from common and shared
// class loaders
if (getCatalina() != null) {
ClassLoader cl = getCatalina().getParentClassLoader();
// Walk the class loader hierarchy. Stop at the system class loader.
// This will add the shared (if present) and common class loaders
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) {
// Ignore
}
}
}
}
cl = cl.getParent();
}
}
// Initialize our defined Services 初始化service
for (Service service : services) {
service.init();
}
}org.apache.catalina.deploy.NamingResourcesImpl#initInternal
//加载 web.xml 中<resource-ref> 的资源配置
@Override
protected void initInternal() throws LifecycleException {
super.initInternal();
// Set this before we register currently known naming resources to avoid
// timing issues. Duplication registration is not an issue.
resourceRequireExplicitRegistration = true;
//循环创建
for (ContextResource cr : resources.values()) {
try {
MBeanUtils.createMBean(cr);
} catch (Exception e) {
log.warn(sm.getString(
"namingResources.mbeanCreateFail", cr.getName()), e);
}
}
//循环创建多个
for (ContextEnvironment ce : envs.values()) {
try {
MBeanUtils.createMBean(ce);
} catch (Exception e) {
log.warn(sm.getString(
"namingResources.mbeanCreateFail", ce.getName()), e);
}
}
for (ContextResourceLink crl : resourceLinks.values()) {
try {
MBeanUtils.createMBean(crl);
} catch (Exception e) {
log.warn(sm.getString(
"namingResources.mbeanCreateFail", crl.getName()), e);
}
}
}org.apache.catalina.core.StandardService#initInternal
执行顺序：initInternal->org.apache.catalina.core.StandardEngine#initInternal->connector.init();
@Override
protected void initInternal() throws LifecycleException {
super.initInternal();
if (engine != null) {
//初始化engine的角色信息
engine.init();
}
// Initialize any Executors 在tomcat8后以后在web.xml中被屏蔽了
for (Executor executor : findExecutors()) {
if (executor instanceof JmxEnabled) {
((JmxEnabled) executor).setDomain(getDomain());
}
executor.init();
}
// Initialize mapper listener 初始化生命周期bean中
mapperListener.init();
// Initialize our defined Connectors 同步对象锁
synchronized (connectorsLock) {
//初始化多个connector
for (Connector connector : connectors) {
try {
connector.init();
} catch (Exception e) {
String message = sm.getString(
"stxandardService.connector.initFailed", connector);
log.error(message, e);
if (Boolean.getBoolean("org.apache.catalina.startup.EXIT_ON_INIT_FAILURE")) {
throw new LifecycleException(message);
}
}
}
}
}#注册到bean
org.apache.catalina.util.LifecycleMBeanBase#initInternal
@Override
protected void initInternal() throws LifecycleException {
// If oname is not null then registration has already happened via
// preRegister().
if (oname == null) {
mserver = Registry.getRegistry(null, null).getMBeanServer();
oname = register(this, getObjectNameKeyProperties());
}
}org.apache.catalina.connector.Connector#initInternal
@Override
protected void initInternal() throws LifecycleException {
super.initInternal();
// Initialize adapter
adapter = new CoyoteAdapter(this);
protocolHandler.setAdapter(adapter);
// 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 {
protocolHandler.init();
} catch (Exception e) {
throw new LifecycleException(
sm.getString("coyoteConnector.protocolHandlerInitializationFailed"), e);
}
}#初始化httpnio
org.apache.coyote.http11.AbstractHttp11Protocol#init
@Override
public void init() throws Exception {
// Upgrade protocols have to be configured first since the endpoint
// init (triggered via super.init() below) uses this list to configure
// the list of ALPN protocols to advertise
for (UpgradeProtocol upgradeProtocol : upgradeProtocols) {
configureUpgradeProtocol(upgradeProtocol);
}
super.init();
// Set the Http11Protocol (i.e. this) for any upgrade protocols once
// this has completed initialisation as the upgrade protocols may expect this
// to be initialised when the call is made
for (UpgradeProtocol upgradeProtocol : upgradeProtocols) {
if (upgradeProtocol instanceof Http2Protocol) {
((Http2Protocol) upgradeProtocol).setHttp11Protocol(this);
}
}
}shutdownhook关闭钩子（优雅关闭）
protected class CatalinaShutdownHook extends Thread {
@Override
public void run() {
try {
if (getServer() != null) {
Catalina.this.stop();
}
} catch (Throwable ex) {
ExceptionUtils.handleThrowable(ex);
log.error(sm.getString("catalina.shutdownHookFail"), ex);
} finally {
// If JULI is used, shut JULI down *after* the server shuts down
// so log messages aren't lost
LogManager logManager = LogManager.getLogManager();
if (logManager instanceof ClassLoaderLogManager) {
((ClassLoaderLogManager) logManager).shutdown();
}
}
}
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();
// 创建解析器(核心方法)
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;
}
//进行双向绑定 绑定到server中，而catalina也可以获取到server。
getServer().setCatalina(this);
getServer().setCatalinaHome(Bootstrap.getCatalinaHomeFile());
getServer().setCatalinaBase(Bootstrap.getCatalinaBaseFile());
// Stream redirection
initStreams();
// Start the new server
try {
//初始化服务操作
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)));
}
}}org.apache.catalina.startup.Catalina#initNaming
protected void initNaming() {
// Setting additional variables
if (!useNaming) {
log.info(sm.getString("catalina.noNaming"));
System.setProperty("catalina.useNaming", "false");
} else {
//设置系统属性catalina.useNaming 为true
System.setProperty("catalina.useNaming", "true");
String value = "org.apache.naming";
String oldValue =
System.getProperty(javax.naming.Context.URL_PKG_PREFIXES);
//如果系统属性中该值已存在 则将新值：老值这样拼上;
if (oldValue != null) {
value = value + ":" + oldValue;
}
//设置java.naming.factory.url.pkgs 为 org.apache.naming
System.setProperty(javax.naming.Context.URL_PKG_PREFIXES, value);
if( log.isDebugEnabled() ) {
log.debug("Setting naming prefix=" + value);
}
//获取系统属性java.naming.factory.initial
value = System.getProperty
(javax.naming.Context.INITIAL_CONTEXT_FACTORY);
if (value == null) {
System.setProperty
(javax.naming.Context.INITIAL_CONTEXT_FACTORY,
"org.apache.naming.java.javaURLContextFactory");
} else {
log.debug( "INITIAL_CONTEXT_FACTORY already set " + value );
}
}
}所有的生命期都在lifecyclebase进行管理
org.apache.catalina.util.LifecycleBase#init
@Override
public final synchronized void init() throws LifecycleException {
if (!state.equals(LifecycleState.NEW)) {
invalidTransition(Lifecycle.BEFORE_INIT_EVENT);
}
try {
//设置生命周期状态
setStateInternal(LifecycleState.INITIALIZING, null, false);
initInternal();
setStateInternal(LifecycleState.INITIALIZED, null, false);
} catch (Throwable t) {
handleSubClassException(t, "lifecycleBase.initFail", toString());
}
}位置：org.apache.catalina.connector.Connector#setProtocol（用于设置协议 tomcat高版本默认为nio，而协议为http 1.1）
public void setProtocol(String protocol) {
boolean aprConnector = AprLifecycleListener.isAprAvailable() &&
AprLifecycleListener.getUseAprConnector();
if ("HTTP/1.1".equals(protocol) || protocol == null) {
if (aprConnector) {
setProtocolHandlerClassName("org.apache.coyote.http11.Http11AprProtocol");
} else {
setProtocolHandlerClassName("org.apache.coyote.http11.Http11NioProtocol");
}
} else if ("AJP/1.3".equals(protocol)) {
if (aprConnector) {
setProtocolHandlerClassName("org.apache.coyote.ajp.AjpAprProtocol");
} else {
setProtocolHandlerClassName("org.apache.coyote.ajp.AjpNioProtocol");
}
} else {
setProtocolHandlerClassName(protocol);
}
}最终进入方法：org.apache.catalina.startup.Catalina#start ，那么整个启动就完毕了。但是要注意下面的这个await(); ，启动到这里就一直阻塞了，每隔10秒就检测一次，当stopAwait为true时，线程才结束。
/**
* Start a new server instance.
*/
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();
// Start the new server 启动服务
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");
}
// 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);
}
}
//await就是主线程的守护，否则就直接关闭了
if (await) {
await();
//当上面的结束后，才会执行下面的关闭，如果没有就一直等待中,当关闭线程的时候，不会直接就关闭，因为tomcat使用卫钩子函数，通过这个可以优雅关闭。
stop();
}
}最后
以上为tomcat启动的核心流程，只挑了一些重点的了解，其实tomcat还有很多非常细节没有涉及到，由于篇幅有限所以，在后续如果需要的时候再标出，还有原因上传gitee上面有需要同步可以拉源码了解。
参考：《Tomcat架构解析》
本文参与 腾讯云自媒体同步曝光计划，分享自微信公众号。
原始发表：2022-07-15，如有侵权请联系 cloudcommunity@tencent.com 删除
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