• Introduction
• Attributes
  1. Common Attributes
  2. Standard Implementation
• Nested Components

A Listener element defines a component that performs actions when specific events occur, usually Tomcat starting or Tomcat stopping.

Listeners may be nested inside a Server, Engine, Host or Context. Some Listeners are only intended to be nested inside specific elements. These constraints are noted in the documentation below.

Common Attributes

All implementations of Listener support the following attributes: Attribute Description className Java class name of the implementation to use. This class must implement the org.apache.catalina.LifecycleListener interface.

Standard Implementation

Unlike most Catalina components, there are several standard Listener implementations available. As a result, the className attribute MUST be used to select the implementation you wish to use. APR Lifecycle Listener (org.apache.catalina.core.AprLifecycleListener) The APR Lifecycle Listener checks for the presence of the APR/native library and loads the library if it is present. For more information see the APR/native guide. This listener must only be nested within Server elements. The following additional attributes are supported by the APR Lifecycle Listener: Attribute Description SSLEngine Name of the SSLEngine to use. off: Do not use SSL, on: Use SSL but no specific ENGINE. The default value is on. This initializes the native SSL engine, which must be enabled in the APR/native connector by the use of the SSLEnabled attribute. See the Official OpenSSL website for more details on supported SSL hardware engines and manufacturers. SSLRandomSeed Entropy source used to seed the SSLEngine's PRNG. The default value is builtin. On development systems, you may want to set this to /dev/urandom to allow quicker start times. Jasper Listener (org.apache.catalina.core.JasperListener) The Jasper Listener initializes the Jasper 2 JSP engine before any web applications that may use it are loaded. For more information on the Jasper 2 JSP engine see the Jasper How To. This listener must only be nested within Server elements. No additional attributes are supported by the Jasper Listener . Server Lifecycle Listener (org.apache.catalina.mbeans.ServerLifecycleListener) The Server Lifecycle Listener initializes the MBeanServer for the MBeans that may be used to manager Tomcat via JMX. Without this listener, none of the Tomcat MBeans will be available. This listener must only be nested within Server elements. No additional attributes are supported by the Server Lifecycle Listener. Global Resources Lifecycle Listener (org.apache.catalina.mbeans.GlobalResourcesLifecycleListener) The Global Resources Lifecycle Listener initializes the Global JNDI resources defined in server.xml as part of the Global Resources element. Without this listener, none of the Global Resources will be available. This listener must only be nested within Server elements. No additional attributes are supported by the Global Resources Lifecycle Listener. JMX Remote Lifecycle Listener (org.apache.catalina.mbeans.JmxRemoteLifecycleListener) This listener requires catalina-jmx-remote.jar to be placed in $CATALINA_HOME/lib. This jar may be found in the extras directory of the binary download area. The JMX Remote Lifecycle Listener fixes the ports used by the JMX/RMI Server making things much simpler if you need to connect jconsole or a similar tool to a remote Tomcat instance that is running behind a firewall. Only these ports are configured via the listener. The remainder of the configuration is via the standard system properties for configuring JMX. For further information on configuring JMX see Monitoring and Management Using JMX included with the Java SDK documentation. If this listener was configured in server.xml as: <Listener className="org.apache.catalina.mbeans.JmxRemoteLifecycleListener" rmiRegistryPortPlatform="10001" rmiServerPortPlatform="10002" /> with the following system properties set (e.g. in setenv.sh): -Dcom.sun.management.jmxremote.password.file=$CATALINA_BASE/conf/jmxremote.password -Dcom.sun.management.jmxremote.access.file=$CATALINA_BASE/conf/jmxremote.access -Dcom.sun.management.jmxremote.ssl=false $CATALINA_BASE/conf/jmxremote.password containing: admin letmein $CATALINA_BASE/conf/jmxremote.access containing: admin readwrite then opening ports 10001 (RMI Registry) and 10002 (JMX/RMI Server) in your firewall would enable jconsole to connect to a Tomcat instance running behind a firewall using a connection string of the form: service:jmx:rmi://<hostname>:10002/jndi/rmi://<hostname>:10001/jmxrmi with a user name of admin and a password of letmein. Note that the example above does not use SSL. JMX access should be considered equivalent to administrative access and secured accordingly. This listener must only be nested within a Server element. The following additional attributes are supported by the JMX Remote Lifecycle Listener: Attribute Description rmiRegistryPortPlatform The port to be used by the JMX/RMI registry for the Platform MBeans. The replaces the use of the com.sun.management.jmxremote.port system property that should not be set when using this valve. rmiServerPortPlatform The port to be used by the Platform JMX/RMI server. useLocalPorts Should any clients using these ports be forced to use local ports to connect to the the JMX/RMI server. This is useful when tunnelling connections over SSH or similar. Defaults to false. JRE Memory Leak Prevention Listener (org.apache.catalina.core.JreMemoryLeakPreventionListener) The JRE Memory Leak Prevention Listener provides work-arounds for known places where the Java Runtime environment uses the context class loader to load a singleton as this will cause a memory leak if a web application class loader happens to be the context class loader at the time. The work-around is to initialise these singletons when this listener starts as Tomcat's common class loader is the context class loader at that time. It also provides work-arounds for known issues that can result in locked JAR files. This listener must only be nested within Server elements. The following additional attributes are supported by the JRE Memory Leak Prevention Listener: Attribute Description appContextProtection Enables protection so that calls to sun.awt.AppContext.getAppContext() triggered by a web application do not result in a memory leak. Note that a call to this method will be triggered as part of the web application stop process so it is strongly recommended that this protection is enabled. The default is true gcDaemonProtection Enables protection so that calls to sun.misc.GC.requestLatency(long) triggered by a web application do not result in a memory leak. Use of RMI is likely to trigger a call to this method. A side effect of enabling this protection is the creation of a thread named "GC Daemon". The protection is uses reflection to access internal Sun classes and may generate errors on startup on non-Sun JVMs. The default is true. urlCacheProtection Enables protection so that reading resources from JAR files using java.net.URLConnections does not result in the JAR file being locked. Note that enabling this protection disables caching by default for all resources obtained via java.net.URLConnections. Caching may be re-enabled on a case by case basis as required. Defaults to true. xmlParsingProtection Enables protection so that parsing XML files within a web application does not result in a memory leak. Note that memory profilers may not display the GC root associated with this leak making it particularly hard to diagnose. Defaults to true.

No element may be nested inside a Listener.