Tomcat架构设计及Servlet作用规范讲解

public class ServletTwoImpl extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        // 1、参数传递
        ServletContext servletContext = this.getServletContext() ;
        String value = String.valueOf(servletContext.getAttribute("name")) ;
        System.out.println("value="+value);
        // 2、获取初始化参数
        String userName= servletContext.getInitParameter("user-name") ;
        System.out.println("userName="+userName);
        // 3、获取应用信息
        String servletContextName = servletContext.getServletContextName() ;
        System.out.println("servletContextName="+servletContextName);
        // 4、获取路径
        String pathOne = servletContext.getRealPath("/") ;
        String pathTwo = servletContext.getRealPath("/WEB-INF/") ;
        System.out.println("pathOne="+pathOne+";pathTwo="+pathTwo);
        response.getWriter().print("执行：doGet; value："+value);
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<Server port="8005" shutdown="SHUTDOWN">
  <Service name="Catalina">
    <Executor name="tomcatThreadPool" namePrefix="catalina-exec-"
        maxThreads="150" minSpareThreads="4"/>
    <Connector port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443" />
    <Connector executor="tomcatThreadPool"
               port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443" />
    <Engine name="Catalina" defaultHost="localhost">
      <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">
        <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>
  </Service>
</Server>

<Server>
    <Service>
        <Connector />
        <Connector />
        <Engine>
            <Host>
                <Context /><!-- 现在常常使用自动部署，不推荐配置Context元素，Context小节有详细说明 -->
            </Host>
        </Engine>
    </Service>
</Server>