Tomcat的Engine初始化，启动过程： http://donald-draper.iteye.com/blog/2327119（看完这篇文章，再看Engine初始化，启动过程）
通过分析Tomcat的启动过程，我们可以看出Tomcat的Server的启动关键在
load方法和start方法，如下：
public class Catalina {
protected String configFile = "conf/server.xml";
protected Server server = null;
//加载Server实例
public void load() {
getServer().setCatalina(this);
try {
//初始化Server
getServer().init();
}
public void start() {
if (getServer() == null) {
//加载Server实例
load();
}
long t1 = System.nanoTime();
try {
//启动Server
getServer().start();
}
}
}
而这两个方法都是调用的Server方法，下面来看一下StandardServer的这两个方法
//<Server>
public final class StandardServer extends LifecycleMBeanBase implements Server {
//看到一下变量,是否会想到Server.xml中的<Server>配置项
//<GlobalNamingResources>
private javax.naming.Context globalNamingContext = null;
private NamingResources globalNamingResources = null;
private static final String info =
"org.apache.catalina.core.StandardServer/1.0";
private NamingContextListener namingContextListener = null;
//<Server port="8005" shutdown="SHUTDOWN">
private int port = 8005;
private String address = "localhost";
private Random random = null;
<Service name="Catalina">
private Service services[] = new Service[0];
private final Object servicesLock = new Object();
private String shutdown = "SHUTDOWN";
private static final StringManager sm =
StringManager.getManager(Constants.Package);
PropertyChangeSupport support = new PropertyChangeSupport(this);
private volatile boolean stopAwait = false;
private Catalina catalina = null;
private ClassLoader parentClassLoader = null;
private volatile Thread awaitThread = null;
private volatile ServerSocket awaitSocket = null;
}
Catatlina的load方法实际上，是调用的Server.init方法，F3到init的定义，我们
可以看到这个方法是在Lifecycle类中
public interface Lifecycle {
//生命周期状态事件
public static final String BEFORE_INIT_EVENT = "before_init";
public static final String AFTER_INIT_EVENT = "after_init";
public static final String START_EVENT = "start";
public static final String BEFORE_START_EVENT = "before_start";
public static final String AFTER_START_EVENT = "after_start";
public static final String STOP_EVENT = "stop";
public static final String BEFORE_STOP_EVENT = "before_stop";
public static final String AFTER_STOP_EVENT = "after_stop";
public static final String AFTER_DESTROY_EVENT = "after_destroy";
public static final String BEFORE_DESTROY_EVENT = "before_destroy";
public static final String PERIODIC_EVENT = "periodic";
public static final String CONFIGURE_START_EVENT = "configure_start";
public static final String CONFIGURE_STOP_EVENT = "configure_stop";
//留给子类扩展
public void init() throws LifecycleException;
}
实际上Tomcat容器中Server，Service，Container（Engine，HOST），Connector的生命周期都是通过Lifecycle
来管理，StandardServer extends LifecycleMBeanBase，我们来查看一下
//LifecycleMBeanBase，JMX管理MBeanServer
public abstract class LifecycleMBeanBase extends LifecycleBase{
private String domain = null;
private ObjectName oname = null;
protected MBeanServer mserver = null;
@Override
//注册Mbean到JMX
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());
}
}
}
再查看LifecycleBase
public abstract class LifecycleBase implements Lifecycle {
@Override
public final synchronized void init() throws LifecycleException {
if (!state.equals(LifecycleState.NEW)) {
invalidTransition(Lifecycle.BEFORE_INIT_EVENT);
}
setStateInternal(LifecycleState.INITIALIZING, null, false);
try {
//这个就是我们要找的Server，load过程的切入点；
initInternal();
} catch (Throwable t) {
ExceptionUtils.handleThrowable(t);
setStateInternal(LifecycleState.FAILED, null, false);
throw new LifecycleException(
sm.getString("lifecycleBase.initFail",toString()), t);
}
setStateInternal(LifecycleState.INITIALIZED, null, false);
}
//留给子类扩展
protected abstract void initInternal() throws LifecycleException;
}
//来看一下LifecycleState
public enum LifecycleState {
NEW(false, null),
INITIALIZING(false, Lifecycle.BEFORE_INIT_EVENT),
INITIALIZED(false, Lifecycle.AFTER_INIT_EVENT),
STARTING_PREP(false, Lifecycle.BEFORE_START_EVENT),
STARTING(true, Lifecycle.START_EVENT),
STARTED(true, Lifecycle.AFTER_START_EVENT),
STOPPING_PREP(true, Lifecycle.BEFORE_STOP_EVENT),
STOPPING(false, Lifecycle.STOP_EVENT),
STOPPED(false, Lifecycle.AFTER_STOP_EVENT),
DESTROYING(false, Lifecycle.BEFORE_DESTROY_EVENT),
DESTROYED(false, Lifecycle.AFTER_DESTROY_EVENT),
FAILED(false, null),
MUST_STOP(true, null),
MUST_DESTROY(false, null);
private final boolean available;
private final String lifecycleEvent;
private LifecycleState(boolean available, String lifecycleEvent) {
this.available = available;
this.lifecycleEvent = lifecycleEvent;
}
public boolean isAvailable() {
return available;
}
public String getLifecycleEvent() {
return lifecycleEvent;
}
}
从LifecycleBase的init方法可以看出，init方法实际上，调用的是initInternal方法，
而这个方法为抽象，待子类去扩展，而生命周期的状态是通过LifecycleState（ ENUM ）
枚举类描述。
现在回到Server的initInternal的方法：
//<Server>
public final class StandardServer extends LifecycleMBeanBase implements Server {
@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");
//注册MBeanFactory
MBeanFactory factory = new MBeanFactory();
factory.setContainer(this);
onameMBeanFactory = register(factory, "type=MBeanFactory");
//注册全局命名资源
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);
}
}
}
}
}
cl = cl.getParent();
}
}
// 初始化Service
for (int i = 0; i < services.length; i++) {
// 初始化Service
services[i].init();
}
}
}
//下面来分析 getServer().start()，Server的start方法与init的方法类似，定义在
Lifecycle，实现在LifecycleBase,我们来看LifecycleBase
public abstract class LifecycleBase implements Lifecycle {
@Override
public final synchronized void start() throws LifecycleException {
if (LifecycleState.STARTING_PREP.equals(state) || LifecycleState.STARTING.equals(state) ||
LifecycleState.STARTED.equals(state)) {
if (log.isDebugEnabled()) {
Exception e = new LifecycleException();
log.debug(sm.getString("lifecycleBase.alreadyStarted", toString()), e);
} else if (log.isInfoEnabled()) {
log.info(sm.getString("lifecycleBase.alreadyStarted", toString()));
}
return;
}
if (state.equals(LifecycleState.NEW)) {
init();
} else if (state.equals(LifecycleState.FAILED)) {
stop();
} else if (!state.equals(LifecycleState.INITIALIZED) &&
!state.equals(LifecycleState.STOPPED)) {
invalidTransition(Lifecycle.BEFORE_START_EVENT);
}
setStateInternal(LifecycleState.STARTING_PREP, null, false);
try {
//关键切入点
startInternal();
}
if (state.equals(LifecycleState.FAILED)) {
stop();
} else if (!state.equals(LifecycleState.STARTING)) {
invalidTransition(Lifecycle.AFTER_START_EVENT);
} else {
setStateInternal(LifecycleState.STARTED, null, false);
}
}
//留给父类扩展
protected abstract void startInternal() throws LifecycleException;
}
再回到现在回到Server的startInternal的方法：
//<Server>
public final class StandardServer extends LifecycleMBeanBase implements Server {
@Override
protected void startInternal() throws LifecycleException {
//触发CONFIGURE_START_EVENT事件
fireLifecycleEvent(CONFIGURE_START_EVENT, null);
//设置状态为开始
setState(LifecycleState.STARTING);
globalNamingResources.start();
// Start our defined Services
synchronized (servicesLock) {
for (int i = 0; i < services.length; i++) {
//启动Service
services[i].start();
}
}
}
}
我们再来看一下StandardServer的addService方法
//添加Service
@Override
public void addService(Service service) {
//将Service与Server关联
service.setServer(this);
synchronized (servicesLock) {
//下面几行代码很有意义，用的是数组而不是 List 集合，
//这个从性能角度考虑可以理解，有趣的是这里用了数组但是并没有向我们平常那样，
//一开始就分配一个固定大小的数组，
//它这里的实现机制是：重新创建一个当前大小的数组对象，
//然后将原来的数组对象 copy 到新的数组中，这种方式实现了类似的动态数组的功能，
//这种实现方式，值得我们以后拿来借鉴。
Service results[] = new Service[services.length + 1];
System.arraycopy(services, 0, results, 0, services.length);
results[services.length] = service;
services = results;
if (getState().isAvailable()) {
try {
//启动service
service.start();
}
}
// Report this property change to interested listeners
support.firePropertyChange("service", null, service);
}
}
至此，Server的init和Start方法已经分析完，下面我们来看一下StandardService,从以上的分析，
我们只需要查看initInternal和startInternal即可
//<Service name="Catalina">
public class StandardService extends LifecycleMBeanBase implements Service {
private static final String info =
"org.apache.catalina.core.StandardService/1.0";
// <Service name="Catalina">
private String name = null;
private static final StringManager sm =
StringManager.getManager(Constants.Package);
private Server server = null;
protected PropertyChangeSupport support = new PropertyChangeSupport(this);
/*<Connector port="8080" protocol="HTTP/1.1"
connectionTimeout="20000"
redirectPort="8443" />
<!-- A "Connector" using the shared thread pool-->
<!--
<Connector executor="tomcatThreadPool"
port="8080" protocol="HTTP/1.1"
connectionTimeout="20000"
redirectPort="8443" />
-->
<!-- Define a SSL HTTP/1.1 Connector on port 8443
This connector uses the BIO implementation that requires the JSSE
style configuration. When using the APR/native implementation, the
OpenSSL style configuration is required as described in the APR/native
documentation -->
<!--
<Connector port="8443" protocol="org.apache.coyote.http11.Http11Protocol"
maxThreads="150" SSLEnabled="true" scheme="https" secure="true"
clientAuth="false" sslProtocol="TLS" />
-->
<!-- Define an AJP 1.3 Connector on port 8009 -->
<Connector port="8009" protocol="AJP/1.3" redirectPort="8443" />
*/
protected Connector connectors[] = new Connector[0];
private final Object connectorsLock = new Object();
/*<!--The connectors can use a shared executor, you can define one or more named thread pools-->
<!--
<Executor name="tomcatThreadPool" namePrefix="catalina-exec-"
maxThreads="150" minSpareThreads="4"/>
-->*/
//线程执行器
protected ArrayList<Executor> executors = new ArrayList<Executor>();
/*
<!-- You should set jvmRoute to support load-balancing via AJP ie :
<Engine name="Catalina" defaultHost="localhost" jvmRoute="jvm1">
-->
<Engine name="Catalina" defaultHost="localhost">
<!--
<Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/>
-->
<!-- Use the LockOutRealm to prevent attempts to guess user passwords
via a brute-force attack -->
<Realm className="org.apache.catalina.realm.LockOutRealm">
<!-- This Realm uses the UserDatabase configured in the global JNDI
resources under the key "UserDatabase". Any edits
that are performed against this UserDatabase are immediately
available for use by the Realm. -->
<Realm className="org.apache.catalina.realm.UserDatabaseRealm"
resourceName="UserDatabase"/>
</Realm>
<Host name="localhost" appBase="webapps"
unpackWARs="true" autoDeploy="true">
<Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs"
prefix="localhost_access_log." suffix=".txt"
pattern="%h %l %u %t "%r" %s %b" />
</Host>
</Engine>*/
//Engine,Host,Realm,都是Container
protected Container container = null;
private ClassLoader parentClassLoader = null;
@Override
protected void initInternal() throws LifecycleException {
//注册Service到JMX
super.initInternal();
//初始化Container
if (container != null) {
container.init();
}
//初始化Executors
for (Executor executor : findExecutors()) {
if (executor instanceof LifecycleMBeanBase) {
((LifecycleMBeanBase) executor).setDomain(getDomain());
}
executor.init();
}
synchronized (connectorsLock) {
for (Connector connector : connectors) {
try {
//初始化Connector
connector.init();
}
}
}
}
@Override
protected void startInternal() throws LifecycleException {
if(log.isInfoEnabled())
log.info(sm.getString("standardService.start.name", this.name));
//设置Service状态
setState(LifecycleState.STARTING);
if (container != null) {
synchronized (container) {
//启动container
container.start();
}
}
synchronized (executors) {
for (Executor executor: executors) {
//启动executor
executor.start();
}
}
synchronized (connectorsLock) {
for (Connector connector: connectors) {
try {
if (connector.getState() != LifecycleState.FAILED) {
//启动connector
connector.start();
}
}
}
}
}
* Set the <code>Container</code> that handles requests for all
* <code>Connectors</code> associated with this Service.
/*<Service>
<Engine>
</Engine>
</Service>*/
//Container处理所有请求
public void setContainer(Container container) {
Container oldContainer = this.container;
if ((oldContainer != null) && (oldContainer instanceof Engine))
((Engine) oldContainer).setService(null);
this.container = container;
if ((this.container != null) && (this.container instanceof Engine))
((Engine) this.container).setService(this);
if (getState().isAvailable() && (this.container != null)) {
try {
//启动Engine
this.container.start();
}
}
if (getState().isAvailable() && (oldContainer != null)) {
try {
oldContainer.stop();
}
}
// Report this property change to interested listeners
support.firePropertyChange("container", oldContainer, this.container);
}
//添加Connector
public void addConnector(Connector connector) {
synchronized (connectorsLock) {
//这个与Server.addService一样的理念
connector.setService(this);
Connector results[] = new Connector[connectors.length + 1];
System.arraycopy(connectors, 0, results, 0, connectors.length);
results[connectors.length] = connector;
connectors = results;
if (getState().isAvailable()) {
try {
connector.start();
}
}
// Report this property change to interested listeners
support.firePropertyChange("connector", null, connector);
}
}
//添加Executor
public void addExecutor(Executor ex) {
synchronized (executors) {
if (!executors.contains(ex)) {
executors.add(ex);
if (getState().isAvailable())
try {
ex.start();
}
}
}
}
}
//Constants
public class Constants {
public static final String Package = "org.apache.catalina.core";
public static final int MAJOR_VERSION = 3;
public static final int MINOR_VERSION = 0;
public static final String JSP_SERVLET_CLASS =
"org.apache.jasper.servlet.JspServlet";
}
从分析StandardService可以看出StandardService主要组成部分为Container（Engine）
，Executors，Connectors，initInternal与startInternal分别初始化和启动Container（Engine），Executors，Connectors。
总结 ：实际上Tomcat容器中Server，Service，Container（Engine，HOST），Connector的生命周期都是通过Lifecycle来管理，Catalina依托于Server，而Server的服务对象为Service；Service的主要组成部分为Container（Engine），Executors，Connectors，Server的初始化与启动实际上，为初始化和启动Container（Engine），Executors，Connectors，下面的章节，我们分别来讲Container（Engine），Executors，Connectors