webapps/docs/architecture/startup.xml - tomcat - Git at Google

 <?xml version="1.0" encoding="UTF-8"?>
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   Licensed to the Apache Software Foundation (ASF) under one or more
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   The ASF licenses this file to You under the Apache License, Version 2.0
   (the "License"); you may not use this file except in compliance with
   the License.  You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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 <!DOCTYPE document [
   <!ENTITY project SYSTEM "project.xml">
 ]>
 <document url="startup.html">

   &project;

   <properties>
     <title>Startup</title>
   </properties>

 <body>


 <section name="Server Startup">

 <p>
 This page describes how the Tomcat server starts up.  There are several
 different ways to start tomcat, including:
 </p>
 <ul>
   <li>From the command line.</li>
   <li>From a Java program as an embedded server.</li>
   <li>Automatically as a Windows service.</li>
 </ul>

 <p>
 A series of UML diagrams have been created to document the start-up process for
 Tomcat.
 </p>
 <p>
 <a href="startup/1_overview.png">Diagram 1</a> shows an overview of how Tomcat
 start, serves requests and then stops. Once the class loaders have been
 initialized, Tomcat parses server.xml using the Digester and the Digester
 creates the objects defined in server.xml, configures them using the property
 values defined in server.xml and the starts the Server. The main Java thread
 waits in the await() method for a shutdown signal. Once a shutdown signal is
 received, the Server object is stopped and then destroyed. The JVM then exits.
 </p>
 <p>
 <a href="startup/2_catalina_init.png">Diagram 2</a> shows how Tomcat initializes
 the objects created by the Digester in the previous step and when additional key
 objects are created. A Server may have several Services although it typically
 only has one. Each Service may have multiple Connectors. A Connector instance is
 associated with a single Protocol instance and a single CoyoteAdapter instance.
 </p>
 <p>
 <a href="startup/3_catalina_start_1.png">Diagram 3</a> shows how Tomcat starts
 the objects created by the Digester that were initialized in the previous step.
 This diagram also shows when lifecycle events are fired. There is more detail to
 the starting of the Engine (and other Containers) which is shown in the
 following diagram.
 </p>
 <p>
 <a href="startup/4_catalina_start_2.png">Diagram 4</a> shows how Containers
 (Engines, Hosts, Contexts and Wrappers) start along with any supporting
 Clusters, Realms and Valves.
 </p>
 <p>
 <a href="startup/5_catalina_start_3.png">Diagram 5</a> shows the start process
 for Context elements as it is rather more involved that the other Containers.
 </p>
 <p>
 <a href="startup/6_catalina_host_config.png">Diagram 6</a> shows how the
 HostConfig component responds to lifecycle events triggered by the Host to
 deploy web applications to the Host.</p>
 <p>
 <a href="startup/7_catalina_context_config.png">Diagram 7</a> shows how the
 ContextConfig component responds to lifecycle events triggered by the Context to
 parse the global and application provided configuration files to create a merged
 web.xml file that is then used, along with other settings, to configure the web
 application.
 </p>

 <p>
 The startup process can be customized in many ways by implementing your own
 LifecycleListeners which are then registered in the server.xml configuration
 file.
 </p>

 </section>

 </body>
 </document>
	<?xml version="1.0" encoding="UTF-8"?>
	<!--
	Licensed to the Apache Software Foundation (ASF) under one or more
	contributor license agreements. See the NOTICE file distributed with
	this work for additional information regarding copyright ownership.
	The ASF licenses this file to You under the Apache License, Version 2.0
	(the "License"); you may not use this file except in compliance with
	the License. You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
	-->
	<!DOCTYPE document [
	<!ENTITY project SYSTEM "project.xml">
	]>
	<document url="startup.html">

	&project;

	<properties>
	<title>Startup</title>
	</properties>

	<body>


	<section name="Server Startup">

	<p>
	This page describes how the Tomcat server starts up. There are several
	different ways to start tomcat, including:
	</p>
	<ul>
	<li>From the command line.</li>
	<li>From a Java program as an embedded server.</li>
	<li>Automatically as a Windows service.</li>
	</ul>

	<p>
	A series of UML diagrams have been created to document the start-up process for
	Tomcat.
	</p>
	<p>
	<a href="startup/1_overview.png">Diagram 1</a> shows an overview of how Tomcat
	start, serves requests and then stops. Once the class loaders have been
	initialized, Tomcat parses server.xml using the Digester and the Digester
	creates the objects defined in server.xml, configures them using the property
	values defined in server.xml and the starts the Server. The main Java thread
	waits in the await() method for a shutdown signal. Once a shutdown signal is
	received, the Server object is stopped and then destroyed. The JVM then exits.
	</p>
	<p>
	<a href="startup/2_catalina_init.png">Diagram 2</a> shows how Tomcat initializes
	the objects created by the Digester in the previous step and when additional key
	objects are created. A Server may have several Services although it typically
	only has one. Each Service may have multiple Connectors. A Connector instance is
	associated with a single Protocol instance and a single CoyoteAdapter instance.
	</p>
	<p>
	<a href="startup/3_catalina_start_1.png">Diagram 3</a> shows how Tomcat starts
	the objects created by the Digester that were initialized in the previous step.
	This diagram also shows when lifecycle events are fired. There is more detail to
	the starting of the Engine (and other Containers) which is shown in the
	following diagram.
	</p>
	<p>
	<a href="startup/4_catalina_start_2.png">Diagram 4</a> shows how Containers
	(Engines, Hosts, Contexts and Wrappers) start along with any supporting
	Clusters, Realms and Valves.
	</p>
	<p>
	<a href="startup/5_catalina_start_3.png">Diagram 5</a> shows the start process
	for Context elements as it is rather more involved that the other Containers.
	</p>
	<p>
	<a href="startup/6_catalina_host_config.png">Diagram 6</a> shows how the
	HostConfig component responds to lifecycle events triggered by the Host to
	deploy web applications to the Host.</p>
	<p>
	<a href="startup/7_catalina_context_config.png">Diagram 7</a> shows how the
	ContextConfig component responds to lifecycle events triggered by the Context to
	parse the global and application provided configuration files to create a merged
	web.xml file that is then used, along with other settings, to configure the web
	application.
	</p>

	<p>
	The startup process can be customized in many ways by implementing your own
	LifecycleListeners which are then registered in the server.xml configuration
	file.
	</p>

	</section>

	</body>
	</document>