環境: tomcat 9.0.36 默認配置
目標: 掌握容器啓動的基本流程,以及一些代碼風格。
需要提前掌握的知識: Tomcat容器的層次結構
Tomcat主函數入口:
Bootstrap.java
synchronized (daemonLock) {
if (daemon == null) {
// 在調用init()之後再設置daemon
Bootstrap bootstrap = new Bootstrap();
try {
//重點,bootstrap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 {
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")) {
調用Catalina的setAwait(),用於start之後的等待
daemon.setAwait(true);
//重點
daemon.load(args);
//重點,下一節再講啓動
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);
}
bootstrap.init();
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");
//重點,Bootstarp其實並非真正地啓動類,它藉助了Object成員變量catalinaDaemon(Catalina)來完成初始化,
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");
//將sharedLoader作爲Catalina的父類加載器
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;
}
initClassLoaders();
private void initClassLoaders() {
try {
commonLoader = createClassLoader("common", null);
if (commonLoader == null) {
// no config file, default to this loader - we might be in a 'single' env.
commonLoader = this.getClass().getClassLoader();
}
catalinaLoader = createClassLoader("server", commonLoader);
sharedLoader = createClassLoader("shared", commonLoader);
} catch (Throwable t) {
handleThrowable(t);
log.error("Class loader creation threw exception", t);
System.exit(1);
}
}
createClassLoader()
private ClassLoader createClassLoader(String name, ClassLoader parent)
throws Exception {
//根據name,獲取value
//value表示從哪幾個地方加載jar包
String value = CatalinaProperties.getProperty(name + ".loader");
if ((value == null) || (value.equals("")))
return parent;
value = replace(value);
List<Repository> repositories = new ArrayList<>();
String[] repositoryPaths = getPaths(value);
for (String repository : repositoryPaths) {
// Check for a JAR URL repository
try {
@SuppressWarnings("unused")
URL url = new URL(repository);
repositories.add(new Repository(repository, RepositoryType.URL));
continue;
} catch (MalformedURLException e) {
// Ignore
}
// Local repository
if (repository.endsWith("*.jar")) {
repository = repository.substring
(0, repository.length() - "*.jar".length());
repositories.add(new Repository(repository, RepositoryType.GLOB));
} else if (repository.endsWith(".jar")) {
repositories.add(new Repository(repository, RepositoryType.JAR));
} else {
repositories.add(new Repository(repository, RepositoryType.DIR));
}
}
//重點
return ClassLoaderFactory.createClassLoader(repositories, parent);
}
ClassLoaderFactory.createClassLoader()中主要通過前面的repositories構造URL[]作爲參數傳入URLClassLoader構造函數中。
return AccessController.doPrivileged(
new PrivilegedAction<URLClassLoader>() {
@Override
public URLClassLoader run() {
if (parent == null)
return new URLClassLoader(array);
else
return new URLClassLoader(array, parent);
}
});
下圖表示URLClassLoader的類圖
daemon.load(args)
public void load() {
if (loaded) {
return;
}
loaded = true;
long t1 = System.nanoTime();
initDirs();
// Before digester - it may be needed
initNaming();
// 主要設置conf/server.xml
ConfigFileLoader.setSource(new CatalinaBaseConfigurationSource(Bootstrap.getCatalinaBaseFile(), getConfigFile()));
File file = configFile();
// Create and execute our Digester
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);
//完成配置conf/server.xml的掃描以及生成server並且調用setServer()
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;
}
//之前已經設置完成server
getServer().setCatalina(this);
getServer().setCatalinaHome(Bootstrap.getCatalinaHomeFile());
getServer().setCatalinaBase(Bootstrap.getCatalinaBaseFile());
// Stream redirection
initStreams();
// Start the new server
try {
//重點
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)));
}
}
getServer().init() 這裏返回的Server是StandardServer類型.
public final synchronized void init() throws LifecycleException {
if (!state.equals(LifecycleState.NEW)) {
invalidTransition(Lifecycle.BEFORE_INIT_EVENT);
}
try {
//設置狀態INITIALIZING,廣播事件
setStateInternal(LifecycleState.INITIALIZING, null, false);
//重點
initInternal();
//設置狀態INITIALIZED,廣播事件
setStateInternal(LifecycleState.INITIALIZED, null, false);
} catch (Throwable t) {
handleSubClassException(t, "lifecycleBase.initFail", toString());
}
}
initInternal()
protected void initInternal() throws LifecycleException {
super.initInternal();
// 初始化utility executor
reconfigureUtilityExecutor(getUtilityThreadsInternal(utilityThreads));
//將它註冊進MBeanServer中
register(utilityExecutor, "type=UtilityExecutor");
// 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 e) {
// Ignore
} catch (IOException e) {
// Ignore
}
}
}
}
cl = cl.getParent();
}
}
// Initialize our defined Services
for (Service service : services) {
//重點
service.init();
}
}
service.init(),非常類似Server的init()
@Override
public final synchronized void init() throws LifecycleException {
if (!state.equals(LifecycleState.NEW)) {
invalidTransition(Lifecycle.BEFORE_INIT_EVENT);
}
try {
setStateInternal(LifecycleState.INITIALIZING, null, false);
//重點
initInternal();
setStateInternal(LifecycleState.INITIALIZED, null, false);
} catch (Throwable t) {
handleSubClassException(t, "lifecycleBase.initFail", toString());
}
}
StandardService.java
protected void initInternal() throws LifecycleException {
super.initInternal();
if (engine != null) {
engine.init();
}
// Initialize any Executors
for (Executor executor : findExecutors()) {
if (executor instanceof JmxEnabled) {
((JmxEnabled) executor).setDomain(getDomain());
}
executor.init();
}
// Initialize mapper listener
mapperListener.init();
// Initialize our defined Connectors
synchronized (connectorsLock) {
//重點
for (Connector connector : connectors) {
connector.init();
}
}
}
StandardEngine.java
public final synchronized void init() throws LifecycleException {
if (!state.equals(LifecycleState.NEW)) {
invalidTransition(Lifecycle.BEFORE_INIT_EVENT);
}
try {
setStateInternal(LifecycleState.INITIALIZING, null, false);
//重點
initInternal();
setStateInternal(LifecycleState.INITIALIZED, null, false);
} catch (Throwable t) {
handleSubClassException(t, "lifecycleBase.initFail", toString());
}
}
protected void initInternal() throws LifecycleException {
//設置用於start,stop流程的線程池
reconfigureStartStopExecutor(getStartStopThreads());
super.initInternal();
}
connector.init()
public final synchronized void init() throws LifecycleException {
if (!state.equals(LifecycleState.NEW)) {
invalidTransition(Lifecycle.BEFORE_INIT_EVENT);
}
try {
setStateInternal(LifecycleState.INITIALIZING, null, false);
initInternal();
setStateInternal(LifecycleState.INITIALIZED, null, false);
} catch (Throwable t) {
handleSubClassException(t, "lifecycleBase.initFail", toString());
}
}
protected void initInternal() throws LifecycleException {
super.initInternal();
if (protocolHandler == null) {
throw new LifecycleException(
sm.getString("coyoteConnector.protocolHandlerInstantiationFailed"));
}
// 通過這個適配器用於調用對應的容器
adapter = new CoyoteAdapter(this);
protocolHandler.setAdapter(adapter);
if (service != null) {
//UtilityExecutor的初始化以及註冊在前面提到過
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 {
//重點
protocolHandler.init();
} catch (Exception e) {
throw new LifecycleException(
sm.getString("coyoteConnector.protocolHandlerInitializationFailed"), e);
}
}
init()
public void init() throws Exception {
if (getLog().isInfoEnabled()) {
getLog().info(sm.getString("abstractProtocolHandler.init", getName()));
logPortOffset();
}
if (oname == null) {
// Component not pre-registered so register it
oname = createObjectName();
if (oname != null) {
Registry.getRegistry(null, null).registerComponent(this, oname, null);
}
}
if (this.domain != null) {
rgOname = new ObjectName(domain + ":type=GlobalRequestProcessor,name=" + getName());
Registry.getRegistry(null, null).registerComponent(
getHandler().getGlobal(), rgOname, null);
}
String endpointName = getName();
endpoint.setName(endpointName.substring(1, endpointName.length()-1));
endpoint.setDomain(domain);
//重點,前面邏輯主要是註冊ProtocolHandler,GlobalRequestProcessor
endpoint.init();
}
endpoint.init()
public final void init() throws Exception {
if (bindOnInit) {
//重點,跟到NioEndpoint的bind方法
bindWithCleanup();
bindState = BindState.BOUND_ON_INIT;
}
if (this.domain != null) {
// Register endpoint (as ThreadPool - historical name)
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);
}
}
}
NioEndpoint.java
public void bind() throws Exception {
//初始化socker ,綁定端口
initServerSocket();
setStopLatch(new CountDownLatch(1));
// Initialize SSL if needed
initialiseSsl();
//通過雙檢鎖創建非阻塞selector,並開啓後臺線程BlockPoller
selectorPool.open(getName());
}