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P51/apache-tomcat-6.0.14/webapps/docs/architecture/startup/serverStartup.txt

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+Tomcat 5 Startup Sequence
+
+Sequence 1. Start from Command Line
+Class: org.apache.catalina.startup.Bootstrap
+What it does:
+	a) Set up classloaders 
+		commonLoader (common)-> System Loader
+		sharedLoader (shared)-> commonLoader -> System Loader
+		catalinaLoader(server) -> commonLoader -> System Loader
+	b) Load startup class (reflection)
+		org.apache.catalina.startup.Catalina
+		setParentClassloader -> sharedLoader
+		Thread.contextClassloader -> catalinaLoader
+	c) Bootstrap.daemon.init() complete
+	
+Sequence 2. Process command line argument (start, startd, stop, stopd)
+Class: org.apache.catalina.startup.Bootstrap (assume command->start)
+What it does: 
+	a) Catalina.setAwait(true);
+	b) Catalina.load()
+		b1) initDirs() -> set properties like 
+		                  catalina.home
+		                  catalina.base == catalina.home (most cases)
+		b2) initNaming
+			setProperty(javax.naming.Context.INITIAL_CONTEXT_FACTORY,
+				    org.apache.naming.java.javaURLContextFactory ->default)
+		b3) createStartDigester() 
+			Configures a digester for the main server.xml elements like
+			org.apache.catalina.core.StandardServer (can change of course :)
+			org.apache.catalina.deploy.NamingResources
+				Stores naming resources in the J2EE JNDI tree
+			org.apache.catalina.LifecycleListener
+				implements events for start/stop of major components
+			org.apache.catalina.core.StandardService
+				The single entry for a set of connectors,
+				so that a container can listen to multiple connectors
+				ie, single entry
+			org.apache.coyote.tomcat5.CoyoteConnector
+				Connectors to listen for incoming requests only
+			It also adds the following rulesets to the digester
+				NamingRuleSet
+				EngineRuleSet
+				HostRuleSet
+				ContextRuleSet
+		b4) Load the server.xml and parse it using the digester
+		    Parsing the server.xml using the digester is an automatic
+		    XML-object mapping tool, that will create the objects defined in server.xml
+		    Startup of the actual container has not started yet.
+		b5) Assigns System.out and System.err to the SystemLogHandler class
+		b6) Calls intialize on all components, this makes each object register itself with the 
+		    JMX agent.
+		    During the process call the Connectors also initialize the adapters.
+		    The adapters are the components that do the request pre-processing.
+		    Typical adapters are HTTP1.1 (default if no protocol is specified,
+		    org.apache.coyote.http11.Http11Protocol)
+		    AJP1.3 for mod_jk etc.
+
+	c) Catalina.start()
+		c1) Starts the NamingContext and binds all JNDI references into it
+		c2) Starts the services under <Server> which are:
+			StandardService -> starts Engine (ContainerBase ->Logger,Loader,Realm,Cluster etc)
+		c3) StandardHost (started by the service)
+				Configures a ErrorReportValvem to do proper HTML output for different HTTP 
+				errors codes
+				Starts the Valves in the pipeline (at least the ErrorReportValve)
+				Configures the StandardHostValve, 
+					this valves ties the Webapp Class loader to the thread context
+					it also finds the session for the request
+					and invokes the context pipeline
+				Starts the HostConfig component
+					This component deploys all the webapps
+						(webapps & conf/Catalina/localhost/*.xml)
+					Webapps are installed using the deployer (StandardHostDeployer)
+					The deployer will create a Digester for your context, this digester
+					will then invoke ContextConfig.start()
+						The ContextConfig.start() will process the default web.xml (conf/web.xml)
+						and then process the applications web.xml (WEB-INF/web.xml)
+						
+		c4) During the lifetime of the container (StandardEngine) there is a background thread that 
+		    keeps checking if the context has changed. If a context changes (timestamp of war file, 
+		    context xml file, web.xml) then a reload is issued (stop/remove/deploy/start)
+		    
+	d) Tomcat receives a request on an HTTP port
+	    d1) The request is received by a separate thread which is waiting in the PoolTcpEndPoint 
+	         class. It is waiting for a request in a regular ServerSocket.accept() method.
+	         When a request is received, this thread wakes up.
+	    d2) The PoolTcpEndPoint assigns the a TcpConnection to handle the request. 
+	        It also supplies a JMX object name to the catalina container (not used I believe)
+	    d3) The processor to handle the request in this case is Coyote Http11Processor, 
+	        and the process method is invoked.
+	        This same processor is also continuing to check the input stream of the socket
+	        until the keep alive point is reached or the connection is disconnected.
+	    d4) The HTTP request is parsed using an internal buffer class (Coyote Http11 Internal Buffer)
+	        The buffer class parses the request line, the headers, etc and store the result in a 
+	        Coyote request (not an HTTP request) This request contains all the HTTP info, such
+	        as servername, port, scheme, etc.
+	    d5) The processor contains a reference to an Adapter, in this case it is the 
+	        Coyote Tomcat 5 Adapter. Once the request has been parsed, the Http11 processor
+	        invokes service() on the adapter. In the service method, the Request contains a 
+	        CoyoteRequest and CoyoteRespons (null for the first time)
+	        The CoyoteRequest(Response) implements HttpRequest(Response) and HttpServletRequest(Response)
+	        The adapter parses and associates everything with the request, cookies, the context through a 
+	        Mapper, etc
+	    d6) When the parsing is finished, the CoyoteAdapter invokes its container (StandardEngine)
+	        and invokes the invoke(request,response) method.
+	        This initiates the HTTP request into the Catalina container starting at the engine level
+	    d7) The StandardEngine.invoke() simply invokes the container pipeline.invoke()
+	    d8) By default the engine only has one valve the StandardEngineValve, this valve simply
+	        invokes the invoke() method on the Host pipeline (StandardHost.getPipeLine())
+	    d9) the StandardHost has two valves by default, the StandardHostValve and the ErrorReportValve
+	    d10) The standard host valve associates the correct class loader with the current thread
+	         It also retrives the Manager and the session associated with the request (if there is one)
+	         If there is a session access() is called to keep the session alive
+	    d11) After that the StandardHostValve invokes the pipeline on the context associated
+	         with the request.
+	    d12) The first valve that gets invoked by the Context pipeline is the FormAuthenticator
+	         valve. Then the StandardContextValve gets invoke.
+	         The StandardContextValve invokes any context listeners associated with the context.
+	         Next it invokes the pipeline on the Wrapper component (StandardWrapperValve)
+	    d13) During the invokation of the StandardWrapperValve, the JSP wrapper (Jasper) gets invoked
+	         This results in the actual compilation of the JSP.
+	         And then invokes the actual servlet.
+	e) Invokation of the servlet class
+	         
+	         
+	         
+	    
+	        
+	        
+	        
+	    
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