二、Tomcat源码分析-Tomcat框架设计

总体架构

tomcat的总体架构如下图所示（摘自http://blog.csdn.net/jiaomingliang/article/details/47393141）

如上图所示，tomcat由Server、Service、Engine、Connerctor、Host、Context组件组成，其中带有s的代表在一个tomcat实例上可以存在多个组件，比如Context(s)，tomcat允许我们部署多个应用，每个应用对应一个Context。这些组件在tomcat的conf/server.xml文件中可以找到，对tomcat的调优需要改动该文件

server.xml
<Service name="Catalina">
    <Connector port="8080" protocol="HTTP/1.1"
           connectionTimeout="20000"
           redirectPort="8443" />
    <Connector port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443" />
    <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" />
    <Engine name="Catalina" defaultHost="localhost">
      <Realm className="org.apache.catalina.realm.LockOutRealm">
        <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>