<Context path="/myApp" docBase="myApp" debug="0" reloadable="true" />

package org.apache.catalina;
import java.beans.PropertyChangeListener;public interface Loader {public ClassLoader getClassLoader();public Container getContainer();public void setContainer(Container container);public DefaultContext getDefaultContext();public void setDefaultContext(DefaultContext defaultContext);public boolean getDelegate();public void setDelegate(boolean delegate);public String getInfo();public boolean getReloadable();public void setReloadable(boolean reloadable); public void addPropertyChangeListener(PropertyChangeListener listener);   public void addRepository(String repository); public String[] findRepositories(); public boolean modified(); public void removePropertyChangeListener(PropertyChangeListener listener);
}

 public void start() throws LifecycleException {// org.apache.catalina.loader.WebappLoader.start()，为了看其 outline，我没有对该method做删减// Validate and update our current component stateif (started)throw new LifecycleException(sm.getString("webappLoader.alreadyStarted"));if (debug >= 1)log(sm.getString("webappLoader.starting"));lifecycle.fireLifecycleEvent(START_EVENT, null);started = true;if (container.getResources() == null)return;// Register a stream handler factory for the JNDI protocolURLStreamHandlerFactory streamHandlerFactory =new DirContextURLStreamHandlerFactory();try {URL.setURLStreamHandlerFactory(streamHandlerFactory);} catch (Throwable t) {// Ignore the error here.}// Construct a class loader based on our current repositories listtry {classLoader = createClassLoader(); // 创建一个类载入器,下面是设置类载入器classLoader.setResources(container.getResources()); classLoader.setDebug(this.debug);classLoader.setDelegate(this.delegate);for (int i = 0; i < repositories.length; i++) {classLoader.addRepository(repositories[i]);}// Configure our repositoriessetRepositories(); // 设置仓库setClassPath(); // 设置类路径setPermissions(); // 设置访问权限if (classLoader instanceof Lifecycle)((Lifecycle) classLoader).start(); // Binding the Webapp class loader to the directory contextDirContextURLStreamHandler.bind((ClassLoader) classLoader, this.container.getResources());} catch (Throwable t) {throw new LifecycleException("start: ", t);}// Validate that all required packages are actually availablevalidatePackages();// Start our background thread if we are reloadableif (reloadable) {log(sm.getString("webappLoader.reloading"));try {threadStart(); // 启动一个新线程来支持自动重载} catch (IllegalStateException e) {throw new LifecycleException(e);}}}

private WebappClassLoader createClassLoader()throws Exception { // org.apache.catalina.loader.WebappLoader.createClassLoader()Class clazz = Class.forName(loaderClass);WebappClassLoader classLoader = null; // highlight line.if (parentClassLoader == null) {// Will cause a ClassCast is the class does not extend WCL, but// this is on purpose (the exception will be caught and rethrown)classLoader = (WebappClassLoader) clazz.newInstance();} else {Class[] argTypes = { ClassLoader.class };Object[] args = { parentClassLoader };Constructor constr = clazz.getConstructor(argTypes);classLoader = (WebappClassLoader) constr.newInstance(args);}return classLoader;}

 private void setRepositories() { // org.apache.catalina.loader.WebappLoader.setRepositories()if (!(container instanceof Context))return;ServletContext servletContext =((Context) container).getServletContext();if (servletContext == null)return;// Loading the work directoryFile workDir =(File) servletContext.getAttribute(Globals.WORK_DIR_ATTR);if (workDir == null)return;log(sm.getString("webappLoader.deploy", workDir.getAbsolutePath()));DirContext resources = container.getResources();// Setting up the class repository (/WEB-INF/classes), if it existsString classesPath = "/WEB-INF/classes";DirContext classes = null;try {Object object = resources.lookup(classesPath);if (object instanceof DirContext) {classes = (DirContext) object;}} catch(NamingException e) {// Silent catch: it's valid that no /WEB-INF/classes collection// exists}if (classes != null) {File classRepository = null;String absoluteClassesPath =servletContext.getRealPath(classesPath);if (absoluteClassesPath != null) {classRepository = new File(absoluteClassesPath);} else {classRepository = new File(workDir, classesPath);classRepository.mkdirs();copyDir(classes, classRepository);}log(sm.getString("webappLoader.classDeploy", classesPath,classRepository.getAbsolutePath()));// Adding the repository to the class loaderclassLoader.addRepository(classesPath + "/", classRepository);}// Setting up the JAR repository (/WEB-INF/lib), if it existsString libPath = "/WEB-INF/lib";classLoader.setJarPath(libPath);DirContext libDir = null;// Looking up directory /WEB-INF/lib in the contexttry {Object object = resources.lookup(libPath);if (object instanceof DirContext)libDir = (DirContext) object;} catch(NamingException e) {// Silent catch: it's valid that no /WEB-INF/lib collection// exists}if (libDir != null) {boolean copyJars = false;String absoluteLibPath = servletContext.getRealPath(libPath);File destDir = null;if (absoluteLibPath != null) {destDir = new File(absoluteLibPath);} else {copyJars = true;destDir = new File(workDir, libPath);destDir.mkdirs();}// Looking up directory /WEB-INF/lib in the contexttry {NamingEnumeration enum = resources.listBindings(libPath);while (enum.hasMoreElements()) {Binding binding = (Binding) enum.nextElement();String filename = libPath + "/" + binding.getName();if (!filename.endsWith(".jar"))continue;// Copy JAR in the work directory, always (the JAR file// would get locked otherwise, which would make it// impossible to update it or remove it at runtime)File destFile = new File(destDir, binding.getName());log(sm.getString("webappLoader.jarDeploy", filename,destFile.getAbsolutePath()));Resource jarResource = (Resource) binding.getObject();if (copyJars) {if (!copy(jarResource.streamContent(),new FileOutputStream(destFile)))continue;}JarFile jarFile = new JarFile(destFile);classLoader.addJar(filename, jarFile, destFile);}} catch (NamingException e) {// Silent catch: it's valid that no /WEB-INF/lib directory// exists} catch (IOException e) {e.printStackTrace();}        }}

private void setClassPath() { // org.apache.catalina.loader.WebappLoader.setClassPath()// Validate our current state informationif (!(container instanceof Context))return;ServletContext servletContext =((Context) container).getServletContext();if (servletContext == null)return;StringBuffer classpath = new StringBuffer();// Assemble the class path information from our class loader chainClassLoader loader = getClassLoader();int layers = 0;int n = 0;while ((layers < 3) && (loader != null)) {if (!(loader instanceof URLClassLoader))break;URL repositories[] =((URLClassLoader) loader).getURLs();for (int i = 0; i < repositories.length; i++) {String repository = repositories[i].toString();if (repository.startsWith("file://"))repository = repository.substring(7);else if (repository.startsWith("file:"))repository = repository.substring(5);else if (repository.startsWith("jndi:"))repository =servletContext.getRealPath(repository.substring(5));elsecontinue;if (repository == null)continue;if (n > 0)classpath.append(File.pathSeparator);classpath.append(repository);n++;}loader = loader.getParent();layers++;}// Store the assembled class path as a servlet context attributeservletContext.setAttribute(Globals.CLASS_PATH_ATTR,classpath.toString());}

private void setPermissions() {// org.apache.catalina.loader.WebappLoader.setPermission()if (System.getSecurityManager() == null)return;if (!(container instanceof Context))return;// Tell the class loader the root of the contextServletContext servletContext =((Context) container).getServletContext();// Assigning permissions for the work directoryFile workDir =(File) servletContext.getAttribute(Globals.WORK_DIR_ATTR);if (workDir != null) {try {String workDirPath = workDir.getCanonicalPath();classLoader.addPermission(new FilePermission(workDirPath, "read,write"));classLoader.addPermission(new FilePermission(workDirPath + File.separator + "-", "read,write,delete"));} catch (IOException e) {// Ignore}} try {URL rootURL = servletContext.getResource("/");classLoader.addPermission(rootURL);String contextRoot = servletContext.getRealPath("/");if (contextRoot != null) {try {contextRoot = (new File(contextRoot)).getCanonicalPath();classLoader.addPermission(contextRoot);} catch (IOException e) {// Ignore}}URL classesURL = servletContext.getResource("/WEB-INF/classes/");classLoader.addPermission(classesURL);URL libURL = servletContext.getResource("/WEB-INF/lib/");classLoader.addPermission(libURL);if (contextRoot != null) {if (libURL != null) {File rootDir = new File(contextRoot);File libDir = new File(rootDir, "WEB-INF/lib/");try {String path = libDir.getCanonicalPath();classLoader.addPermission(path);} catch (IOException e) {}}} else {if (workDir != null) {if (libURL != null) {File libDir = new File(workDir, "WEB-INF/lib/");try {String path = libDir.getCanonicalPath();classLoader.addPermission(path);} catch (IOException e) {}}if (classesURL != null) {File classesDir = new File(workDir, "WEB-INF/classes/");try {String path = classesDir.getCanonicalPath();classLoader.addPermission(path);} catch (IOException e) {}}}}} catch (MalformedURLException e) {}}

 public synchronized void reload() { //org.apache.catalina.core.StandardContext.reload()// Validate our current component stateif (!started)throw new IllegalStateException(sm.getString("containerBase.notStarted", logName()));// Make sure reloading is enabled//      if (!reloadable)//          throw new IllegalStateException//              (sm.getString("standardContext.notReloadable"));log(sm.getString("standardContext.reloadingStarted"));// Stop accepting requests temporarilysetPaused(true);// Binding threadClassLoader oldCCL = bindThread();// Shut down our session managerif ((manager != null) && (manager instanceof Lifecycle)) {try {((Lifecycle) manager).stop();} catch (LifecycleException e) {log(sm.getString("standardContext.stoppingManager"), e);}}// Shut down the current version of all active servletsContainer children[] = findChildren();for (int i = 0; i < children.length; i++) {Wrapper wrapper = (Wrapper) children[i];if (wrapper instanceof Lifecycle) {try {((Lifecycle) wrapper).stop();} catch (LifecycleException e) {log(sm.getString("standardContext.stoppingWrapper",wrapper.getName()),e);}}}// Shut down application event listenerslistenerStop();// Clear all application-originated servlet context attributesif (context != null)context.clearAttributes();// Shut down filtersfilterStop();if (isUseNaming()) {// StartnamingContextListener.lifecycleEvent(new LifecycleEvent(this, Lifecycle.STOP_EVENT));}// Binding threadunbindThread(oldCCL);// Shut down our application class loaderif ((loader != null) && (loader instanceof Lifecycle)) {try {((Lifecycle) loader).stop();} catch (LifecycleException e) {log(sm.getString("standardContext.stoppingLoader"), e);}}// Binding threadoldCCL = bindThread();// Restart our application class loaderif ((loader != null) && (loader instanceof Lifecycle)) {try {((Lifecycle) loader).start();} catch (LifecycleException e) {log(sm.getString("standardContext.startingLoader"), e);}}// Binding threadunbindThread(oldCCL);// Create and register the associated naming context, if internal// naming is usedboolean ok = true;if (isUseNaming()) {// StartnamingContextListener.lifecycleEvent(new LifecycleEvent(this, Lifecycle.START_EVENT));}// Binding threadoldCCL = bindThread();// Restart our application event listeners and filtersif (ok) {if (!listenerStart()) {log(sm.getString("standardContext.listenerStartFailed"));ok = false;}}if (ok) {if (!filterStart()) {log(sm.getString("standardContext.filterStartFailed"));ok = false;}}// Restore the "Welcome Files" and "Resources" context attributespostResources();postWelcomeFiles();// Restart our currently defined servletsfor (int i = 0; i < children.length; i++) {if (!ok)break;Wrapper wrapper = (Wrapper) children[i];if (wrapper instanceof Lifecycle) {try {((Lifecycle) wrapper).start();} catch (LifecycleException e) {log(sm.getString("standardContext.startingWrapper",wrapper.getName()),e);ok = false;}}}// Reinitialize all load on startup servletsloadOnStartup(children);// Restart our session manager (AFTER naming context recreated/bound)if ((manager != null) && (manager instanceof Lifecycle)) {try {((Lifecycle) manager).start();} catch (LifecycleException e) {log(sm.getString("standardContext.startingManager"), e);}}// Unbinding threadunbindThread(oldCCL);// Start accepting requests againif (ok) {log(sm.getString("standardContext.reloadingCompleted"));} else {setAvailable(false);log(sm.getString("standardContext.reloadingFailed"));}setPaused(false);// Notify our interested LifecycleListenerslifecycle.fireLifecycleEvent(Context.RELOAD_EVENT, null);}

private static final String[] triggers = {
"javax.servlet.Servlet"
};

private static final String[] packageTriggers = {"javax","org.xml.sax","org.w3c.dom","org.apache.xerces","org.apache.xalan",
};

public class ResourceEntry { // org.apache.catalina.loader.ResourceEntry/*** The "last modified" time of the origin file at the time this class* was loaded, in milliseconds since the epoch.*/public long lastModified = -1;/*** Binary content of the resource.*/public byte[] binaryContent = null;/*** Loaded class.*/public Class loadedClass = null;/*** URL source from where the object was loaded.*/public URL source = null;/*** URL of the codebase from where the object was loaded.*/public URL codeBase = null;/*** Manifest (if the resource was loaded from a JAR).*/public Manifest manifest = null;/*** Certificates (if the resource was loaded from a JAR).*/public Certificate[] certificates = null;
}

public final class Bootstrap {public static void main(String[] args) {//invoke: http://localhost:8080/Modern or  http://localhost:8080/Primitive
//  为了通知StandardContext 实例到哪里查找应用程序目录，需要设置一个名为"catalina.base"的系统属性，其值为"user.dir"属性的值；System.setProperty("catalina.base", System.getProperty("user.dir"));Connector connector = new HttpConnector(); //实例化默认连接器Wrapper wrapper1 = new SimpleWrapper(); // 为两个servlet类创建两个Wrapper实例；wrapper1.setName("Primitive");wrapper1.setServletClass("PrimitiveServlet");Wrapper wrapper2 = new SimpleWrapper();wrapper2.setName("Modern");wrapper2.setServletClass("ModernServlet");// 创建StandardContext 的一个实例，设置应用程序路径和上下文的文档根路径Context context = new StandardContext();// StandardContext's start method adds a default mappercontext.setPath("/myApp");context.setDocBase("myApp");// 上面的代码在功能上等同于下面的在server.xml 文件中的配置// <Context path="/myApp" docBase="myApp" />context.addChild(wrapper1); // 将两个Wrapper实例添加到Context容器中context.addChild(wrapper2);// 为它们设置访问路径的映射关系，这样Context 容器就能够定位到他们// context.addServletMapping(pattern, name); context.addServletMapping("/Primitive", "Primitive");context.addServletMapping("/Modern", "Modern");// add ContextConfig. This listener is important because it configures// StandardContext (sets configured to true), otherwise StandardContext// won't start// 下一步，实例化一个监听器，并通过 Context容器注册它.LifecycleListener listener = new SimpleContextConfig();((Lifecycle) context).addLifecycleListener(listener);// 接着，它会实例化WebappLoader类，并将其关联到Context容器.// here is our loaderLoader loader = new WebappLoader();// associate the loader with the Contextcontext.setLoader(loader);// 然后，将Context容器与默认连接器相关联，调用默认连接器的initialize() and start()方法，// 再调用 Context容器的 start() 方法，这样servlet容器准备就绪，可以处理servlet请求了.connector.setContainer(context);try {connector.initialize();((Lifecycle) connector).start(); ((Lifecycle) context).start(); // attention: 从这一行开始（包括这一行），进行spec analysis.// 接下来的几行代码仅仅显示出资源的docBase属性值和类载入器中所有的仓库的名字.// now we want to know some details about WebappLoaderWebappClassLoader classLoader = (WebappClassLoader) loader.getClassLoader();System.out.println("Resources' docBase: " + ((ProxyDirContext)classLoader.getResources()).getDocBase());String[] repositories = classLoader.findRepositories();for (int i=0; i<repositories.length; i++) {System.out.println("  repository: " + repositories[i]);}// 最后，用户输入任意键后，程序退出.// make the application wait until we press a key.System.in.read();((Lifecycle) context).stop();}catch (Exception e) {e.printStackTrace();}}
}

E:\bench-cluster\cloud-data-preprocess\HowTomcatWorks\src>java -cp .;lib/servlet.jar;lib/catalina_4_1_24.jar;lib/catalina-5.5.4.jar;lib/naming-resources.jar;lib/naming-common.jar;lib/commons-collectio
ns.jar;lib/catalina.jar;E:\bench-cluster\cloud-data-preprocess\HowTomcatWorks\webroot com.tomcat.chapter8.startup.Bootstrap
HttpConnector Opening server socket on all host IP addresses
HttpConnector[8080] Starting background thread
WebappLoader[/myApp]: Deploying class repositories to work directory E:\bench-cluster\cloud-data-preprocess\HowTomcatWorks\src\work\_\_\myApp
Starting Wrapper Primitive
Starting Wrapper Modern
StandardManager[/myApp]: Seeding random number generator class java.security.SecureRandom
StandardManager[/myApp]: Seeding of random number generator has been completed
Resources' docBase: E:\bench-cluster\cloud-data-preprocess\HowTomcatWorks\src\myApp // this line.Stopping wrapper Primitive
Stopping wrapper ModernE:\bench-cluster\cloud-data-preprocess\HowTomcatWorks\src>

Attention）这里还差了一个打印info， 在this line 下面一行： repository: /WEB-INF/classes/ ；