原文日期:2017-06-01
前面已经讲完了Bootstrap初始化、加载服务,接下来就是Boostrap的启动Bootstrap.start(),如下代码。
/**
* 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);
}
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从上面代码可以看出,实际上Boostrap.start()方法是通过Java反射去调用Catalina.start()方法。如下是Catalina.start()方法代码块。
/**
* 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
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);
}
}
if (await) {
await();
stop();
}
}
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如上,该方法主要进行了如下几个步骤。
-
getServer().start(),即调用StandardServer.start()方法。
-
Runtime.addShutdownHook(new CatalinaShutdownHook()),添加关闭钩子,以便服务关闭时清理释放资源。
-
await(),实际是调用StandardServer.await()去创建ServerSocket,并监听端口。
-
stop(),实际是调用调用StandardServer.stop()停止服务,并释放资源。
总结
到这里,基本上已经完成了tomcat的启动流程。如下是tomcat启动流程时序图