tomcat的启动类在Bootstrap.java中，main方法如下：
/**
* Main method, used for testing only.
*
* @param args Command line arguments to be processed
*/
public static void main(String args[]) {
if (daemon == null) {
daemon = new Bootstrap();
try {
daemon.init();
} catch (Throwable t) {
t.printStackTrace();
return;
}
}
try {
String command = "start";
if (args.length > 0) {
command = args[args.length - 1];
}
if (command.equals("startd")) {
args[0] = "start";
daemon.load(args);
daemon.start();
} else if (command.equals("stopd")) {
args[0] = "stop";
daemon.stop();
} else if (command.equals("start")) {
daemon.setAwait(true);
daemon.load(args);
daemon.start();
} else if (command.equals("stop")) {
daemon.stopServer(args);
} else {
log.warn("Bootstrap: command \"" + command + "\" does not exist.");
}
} catch (Throwable t) {
t.printStackTrace();
}
}
初始化方法：init()
/**
* Initialize daemon.
*/
public void init()
throws Exception
{
// Set Catalina path
setCatalinaHome();
setCatalinaBase();
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.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;
}
tomcat启动时初始化三个类加载器，commonLoader允许加载%CATALINA_HOME%/common/classes, %CATALINA_HOME%/common/endorsed, and %CATALINA_HOME%/common/lib这三个目录下的类，
catalinaLoader负责加载catalina servlet容器运行时需要的类，包括%CATALINA_HOME%/server/classes and %CATALINA_HOME%/server/lib 这两个目录下的类以及所有commonLoader能加载的类，
sharedLoader负责加载 %CATALINA_HOME%/shared/classesand %CATALJNA_HOME%/shared/lib
目录下的类以及所有commonLoader能加载的类。然后sharedLoader被分配给跟部署在tomcat下context相关的应用程序的父加载器。注意：sharedLoader不能加载Catalina内部的类和定义在CLASSPATH环境变量下的类。
protected ClassLoader commonLoader = null;
protected ClassLoader catalinaLoader = null;
protected ClassLoader sharedLoader = null;
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) {
log.error("Class loader creation threw exception", t);
System.exit(1);
}
}
load方法
/**
* Load daemon.
*/
private void load(String[] arguments)
throws Exception {
// Call the load() method
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);
}
start()，stop()，stopServer()，stopServer(String[] arguments)，setAwait(boolean await)
/**
* Start the Catalina daemon.
*/
public void start()
throws Exception {
if( catalinaDaemon==null ) init();
Method method = catalinaDaemon.getClass().getMethod("start", (Class [] )null);
method.invoke(catalinaDaemon, (Object [])null);
}
/**
* Stop the Catalina Daemon.
*/
public void stop()
throws Exception {
Method method = catalinaDaemon.getClass().getMethod("stop", (Class [] ) null);
method.invoke(catalinaDaemon, (Object [] ) null);
}
/**
* Stop the standlone server.
*/
public void stopServer()
throws Exception {
Method method =
catalinaDaemon.getClass().getMethod("stopServer", (Class []) null);
method.invoke(catalinaDaemon, (Object []) null);
}
/**
* Stop the standlone server.
*/
public void stopServer(String[] arguments)
throws Exception {
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("stopServer", paramTypes);
method.invoke(catalinaDaemon, param);
}
/**
* Set flag.
*/
public void setAwait(boolean await)
throws Exception {
Class paramTypes[] = new Class[1];
paramTypes[0] = Boolean.TYPE;
Object paramValues[] = new Object[1];
paramValues[0] = new Boolean(await);
Method method =
catalinaDaemon.getClass().getMethod("setAwait", paramTypes);
method.invoke(catalinaDaemon, paramValues);
}
getCatalinaBase()和getCatalinaHome() 方法，这两个方法的前面的值为空，则取后面的值
/**
* Get the value of the catalina.home environment variable.
*/
public static String getCatalinaHome() {
return System.getProperty("catalina.home",
System.getProperty("user.dir"));
}
/**
* Get the value of the catalina.base environment variable.
*/
public static String getCatalinaBase() {
return System.getProperty("catalina.base", getCatalinaHome());
}