1. server的实例类为：org.apache.catalina.core.StandardServer为顶层容器。

2.二级容器GlobalNamingResources，设置认证用户信息。

<GlobalNamingResources>

<!-- Editable user database that can also be used by

UserDatabaseRealm to authenticate users

-->

<Resource name="UserDatabase" auth="Container"

type="org.apache.catalina.UserDatabase"

description="User database that can be updated and saved"

factory="org.apache.catalina.users.MemoryUserDatabaseFactory"

pathname="conf/tomcat-users.xml" />

</GlobalNamingResources>

3. 二级容器service，包括了多个connector和一个engine

<!-- A "Service" is a collection of one or more "Connectors" that share

a single "Container" Note:  A "Service" is not itself a "Container",

so you may not define subcomponents such as "Valves" at this level.

Documentation at /docs/config/service.html

-->

<Service name="Catalina">
    <Connector port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443" />
    <!-- Define an AJP 1.3 Connector on port 8009 -->
    <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" />
    <Engine name="Catalina" defaultHost="localhost" jvmRoute="jvm1">
    -->
    <Engine name="Catalina" defaultHost="localhost">

3. 三级容器Engine包括Realm和Host。

<Engine name="Catalina" defaultHost="localhost">

<!--For clustering, please take a look at documentation at:

/docs/cluster-howto.html  (simple how to)

/docs/config/cluster.html (reference documentation) -->

<!--

<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">

<!-- SingleSignOn valve, share authentication between web applications

Documentation at: /docs/config/valve.html -->

<!--

<Valve className="org.apache.catalina.authenticator.SingleSignOn" />

-->

<!-- Access log processes all example.

Documentation at: /docs/config/valve.html

Note: The pattern used is equivalent to using pattern="common" -->

<Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs"

prefix="localhost_access_log." suffix=".txt"

pattern="%h %l %u %t &quot;%r&quot; %s %b" />

</Host>

</Engine>

实现类关系

Event-Listerner事件监听模式

事件监听同步模式分两个部分：Event Source和Event Listener：
Event Source：被监听者的事件集合，可能是方法，提供事件的注册加入和移除功能。类似被观察者的集合。
Event Listener：事件的监听者，当事件被触发，所有监听这个事件的监听者将被通知，然后执行自己的Action响应动作。

事件监听异步模式在Source和Listener之间引入event queue，
event queue是一个基于事件的publish-subscribe. 它一种松耦合方式提供不同模块和角色之间异步通讯。它比同步更加松耦合，这样，我们就把Source-Listener改成了publish-queue-subscribe方式。