The root element of the tomcat-server.xml file is <Server>. The attributes of this element represent the characteristics of the entire embedded Tomcat servlet container. The shutdown attribute specifies the command string that the shutdown port number receives via a TCP/IP connection in order to shut down the servlet container. The port attribute specifies the TCP/IP port number that listens for a shutdown message.

The <Listener> XML elements specify the list of lifecycle listeners that monitor and manage the embedded Tomcat servlet container. Each listener class is a Java Management Extensions (JMX) MBean that listens to a specific component of the servlet container and has been programmed to do something at certain lifecycle events of the component, such as before starting up, after stopping, and so on.

The first four <Listener> elements configure standard Tomcat lifecycle listeners. The listener implemented by the com.springsource.server.web.tomcat.ServerLifecycleLoggingListener class is specific to SpringSource dm Server and manages server lifecycle logging.

The <Service> XML element groups together one or more connectors and a single engine. Connectors define a transport mechanism, such as HTTP, that clients use to to send and receive messages to and from the associated service. There are many transports that a client can use, which is why a <Service> element can have many <Connector> elements. The engine then defines how these requests and responses that the connector receives and sends are in turn handled by the servlet container; you can defined only a single <Engine> element for any given <Service> element.

The sample tomcat-server.xml file above includes three <Connector> elements: one for the HTTP transport, one for the HTTPS transport, and one for the AJP transport. The file also includes a single <Engine> element, as required.

The first connector listens for HTTP requests at the 8080 TCP/IP port. The connector, after accepting a connection from a client, waits for a maximum of 20000 milliseconds for a request URI; if it does not receive one from the client by then, the connector times out. If this connector receives a request from the client that requires the SSL transport, the servlet container automatically redirects the request to port 8443.

The second connector is for HTTPS requests. The TCP/IP port that users specify as the secure connection port is 8443. Be sure that you set the value of the redirectPort attribute of your non-SSL connectors to this value to ensure that users that require a secure connection are redirected to the secure port, even if they initially start at the non-secure port. The SSLEnabled attribute specifies that SSL is enabled for this connector. The secure attribute ensures that a call to request.isSecure() from the connecting client always returns true. The scheme attribute ensures that a call to request.getScheme() from the connecting client always returns https when clients use this connector.

The maxThreads attribute specifies that the servlet container creates a maximum of 150 request processing threads, which determines the maximum number of simultaneous requests that can be handled. The clientAuth attribute specifies that the servlet container does not require a certificate chain unless the client requests a resource protected by a security constraint that uses CLIENT-CERT authentication.

The keystoreFile attribute specifies the name of the file that contains the servlet container’s private key and public certificate used in the SSL handshake, encryption, and decryption. You use an alias and password to access this information. In the example, this file is SERVER_HOME/config/keystore. The keystorePass attributes specify the password used to access the keystore.

The third AJP Connector element represents a Connector component that communicates with a web connector via the AJP protocol.

The engine has a logical name of Catalina; this is the name used in all log and error messages so you can easily identify problems. The value of the defaultHost attribute refers to the name of a <Host> child element of <Engine>; this host processes requests directed to host names on this servlet container.

The <Realm> child element of <Engine> represents a database of users, passwords, and mapped roles used for authentication in this service. SpringSource dm Server uses an implementation of the Tomcat 6 Realm interface that authenticates users through the Java Authentication and Authorization Service (JAAS) framework which is provided as part of the standard J2SE API.

With the JAASRealm, you can combine practically any conceivable security realm with Tomcat's container managed authentication. For details, see Realm Configuration.

The <Host> child element represents a virtual host, which is an association of a network name for a server (such as www.mycompany.com) with the particular server on which Catalina is running. The servlet container unpacks Web applications into a directory hierarchy if they are deployed as WAR files. The xmlValidation attribute specifies that the servlet container does not validate XML files when parsing them, or in other words, it accepts invalid XML. The xmlNamespaceAware attribute specifies that the servlet container does not take namespaces into account when reading XML files.

Finally, the org.apache.catalina.valves.AccessLogValve valve creates log files in the same format as those created by standard web servers. The servlet container creates the log files in the SERVER_HOME/serviceability/logs/access directory. The log files are prefixed with the string localhost_access_log., have a suffix of .txt, use a standard format for identifying what should be logged, and do not include DNS lookups of the IP address of the remote host.