Configuration of Apache Tomcat

Configuration of Apache Tomcat

1. What is Apache Tomcat?

Apache Tomcat is an open-source servlet container / JSP engine that implements the Java Servlet, JSP, EL and WebSocket specifications. It can act as a standalone web server (HTTP connector) or behind Apache/IIS/Nginx (AJP connector), executing Java web applications (WARs).

2. Tomcat Directory Structure

Directory	Contents
bin/	Startup/shutdown scripts — startup.bat/.sh, shutdown.bat/.sh, catalina.bat/.sh
conf/	server.xml (main config), web.xml (default web-app), context.xml, tomcat-users.xml (manager roles), catalina.policy
logs/	catalina.out, localhost access logs
webapps/	Deployed web applications — each as a directory or a WAR file
work/	Compiled JSP → servlet classes (temporary)
temp/, lib/	Temp files, shared JARs

A web-app layout inside webapps/myapp: WEB-INF/web.xml (deployment descriptor), WEB-INF/classes/ (servlet classes), WEB-INF/lib/ (JARs), plus JSP/HTML/CSS/JS.

3. conf/server.xml — Key Elements

<Server port="8005" shutdown="SHUTDOWN">       <!-- admin shutdown listener -->
  <Service name="Catalina">
    <!-- HTTP connector: browsers talk here (default 8080) -->
    <Connector port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000" maxThreads="200"
               redirectPort="8443" />

    <!-- AJP connector: Apache mod_jk/mod_proxy_ajp talks here -->
    <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" />

    <Engine name="Catalina" defaultHost="localhost">
      <Realm ... />                            <!-- users/roles (tomcat-users.xml, JDBC, LDAP) -->
      <Host name="localhost" appBase="webapps"
            unpackWARs="true" autoDeploy="true">
        <Context path="/myapp" docBase="myapp"
                 reloadable="true" />          <!-- one web-app context -->
      </Host>
    </Engine>
  </Service>
</Server>

Processing chain: Connector → Engine → Host → Context → Wrapper(servlet), with Valves as interceptors (logging/access) and a thread pool (maxThreads) per connector.

4. Common Configuration Tasks

1. Change the port — edit <Connector port="8080"> → 80; the shutdown port (8005) must also differ from other Tomcats on the box.
2. Deploy an application
   • Copy myapp.war into webapps/ (auto-unpack & deploy), or
   • Create webapps/myapp/ directory, or
   • Add a <Context> element / myapp.xml in conf/Catalina/localhost/, or
   • Use the Manager App (http://localhost:8080/manager/html) — deploy/reload/stop/start/undeploy.
3. Manager access — add to conf/tomcat-users.xml:

   <user username="admin" password="secret" roles="manager-gui,admin-gui"/>
   

4. Enable SSL (HTTPS) — generate a keystore (keytool -genkey -alias tomcat -keystore .keystore), then a connector on 8443:

   <Connector port="8443" protocol="org.apache.coyote.http11.Http11NioProtocol"
              SSLEnabled="true" scheme="https" secure="true"
              keystoreFile=".keystore" keystorePass="changeit" />
   

5. Virtual hosts — extra <Host name="www.shop.com" appBase="/var/webapps"> + DNS entry.
6. JNDI DataSource (DB pooling) — <Resource name="jdbc/shopDB" auth="Container" type="javax.sql.DataSource" .../> in context.xml.
7. Memory tuning — set JAVA_OPTS=-Xms512m -Xmx1024m in catalina.bat/.sh; threads via connector maxThreads; session timeout via web.xml <session-config><session-timeout>30</...>.
8. Logging — conf/logging.properties; access log Valve on the Host.
9. Start/stop — bin/startup.sh (or .bat) / bin/shutdown.sh; verify at http://localhost:8080.

5. Tomcat as a Component of the Web

 Browser --HTTP--> Apache (mod_proxy_ajp) --AJP 8009--> Tomcat --> Servlet/JSP --> DB
 Browser -----------------HTTP 8080---------------------> Tomcat (standalone)

6. Exam Points

• Explain the Tomcat directory structure and the role of server.xml with its connector/engine/host/context elements — 10 marks (very frequent).
• List the steps to deploy a web application in Tomcat (WAR, directory, Manager App) — 7 marks.
• Write the configuration for changing the port / enabling SSL / adding a manager user — 5-7 marks.
• Short note: Tomcat vs Apache HTTP Server (web container vs web server) — 5 marks.