<?xml version="1.0" encoding="UTF-8"?>
<!--
  Licensed to the Apache Software Foundation (ASF) under one or more
  contributor license agreements.  See the NOTICE file distributed with
  this work for additional information regarding copyright ownership.
  The ASF licenses this file to You under the Apache License, Version 2.0
  (the "License"); you may not use this file except in compliance with
  the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
-->
<!DOCTYPE document [
  <!ENTITY project SYSTEM "project.xml">
]>
<document url="listeners.html">

  &project;

  <properties>
    <title>The LifeCycle Listener Component</title>
  </properties>

<body>

<section name="Table of Contents">
<toc/>
</section>

<section name="Introduction">

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

  <p>Listeners may be nested inside a <a href="server.html">Server</a>,
  <a href="engine.html">Engine</a>, <a href="host.html">Host</a> or
  <a href="context.html">Context</a>. Some Listeners are only intended to be
  nested inside specific elements. These constraints are noted in the
  documentation below.</p>

</section>

<section name="Attributes">

  <subsection name="Common Attributes">

    <p>All implementations of <strong>Listener</strong>
    support the following attributes:</p>

    <attributes>

      <attribute name="className" required="true">
        <p>Java class name of the implementation to use. This class must
        implement the <code>org.apache.catalina.LifecycleListener</code>
        interface.</p>
      </attribute>

    </attributes>

  </subsection>

</section>

<section name="Nested Components">

  <p>No element may be nested inside a <strong>Listener</strong>.</p>

</section>

<section name="Standard Implementations">

  <p>Unlike most Catalina components, there are several standard
  <strong>Listener</strong> implementations available.  As a result,
  the <code>className</code> attribute MUST be used to select the
  implementation you wish to use.</p>

  <subsection name="APR Lifecycle Listener - org.apache.catalina.core.AprLifecycleListener">

    <p>The <strong>APR Lifecycle Listener</strong> checks for the presence of
    the APR/native library and loads the library if it is present. For more
    information see the <a href="../apr.html">APR/native guide</a>.</p>

    <p>This listener must only be nested within <a href="server.html">Server</a>
    elements.</p>

    <p>The following additional attributes are supported by the <strong>APR
    Lifecycle Listener</strong>:</p>

    <attributes>

      <attribute name="SSLEngine" required="false">
        <p>Name of the SSLEngine to use. <code>off</code>: do not use SSL,
        <code>on</code>: use SSL but no specific ENGINE.</p>
        <p>The default value is <b>on</b>. This initializes the
        native SSL engine, which must be enabled in the APR/native connector by
        the use of the <code>SSLEnabled</code> attribute.</p>
        <p>See the <a href="http://www.openssl.org/">Official OpenSSL website</a>
        for more details on supported SSL hardware engines and manufacturers.
        </p>
        <p>Tomcat Native 2.x onwards requires SSL so if SSLEngine is set to
        <code>off</code> when using Tomcat Native 2.x onwards, the APR/native
        library will be disabled.</p>
      </attribute>

      <attribute name="SSLRandomSeed" required="false">
        <p>Entropy source used to seed the SSLEngine's PRNG. The default value
        is <code>builtin</code>. On development systems, you may want to set
        this to <code>/dev/urandom</code> to allow quicker start times.</p>
      </attribute>

      <attribute name="FIPSMode" required="false">
        <p>The behaviour of this attribute depends on whether Tomcat Native has
        been compiled against OpenSSL 1.x or OpenSSL 3.x.</p>
        <p>For OpenSSL 1.x: Set to <code>on</code> to request that OpenSSL be in
        FIPS mode (if OpenSSL is already in FIPS mode, it will remain in FIPS
        mode).
        Set to <code>enter</code> to force OpenSSL to enter FIPS mode (an
        error will occur if OpenSSL is already in FIPS mode).
        Set to <code>require</code> to require that OpenSSL <i>already</i> be
        in FIPS mode (an error will occur if OpenSSL is not already in FIPS
        mode).</p>
        <p>For OpenSSL 3.x: <code>on</code>, <code>enter</code> and
        <code>require</code> all behave the same way. If the FIPS provider is
        the default provider, it will be used. If the FIPS provider is not the
        default provider, an error will occur.</p>
        <p>FIPS mode <em>requires you to have a FIPS-capable OpenSSL library</em>.
        If this attribute is set to anything other than <code>off</code>, the
        <b>SSLEngine</b> must be enabled as well.</p>
        <p>The default value is <code>off</code>.</p>
      </attribute>

      <attribute name="useAprConnector" required="false">
        <p>This attribute controls the auto-selection of the connector
        implementation. When the <strong>protocol</strong> is specified as
        <code>HTTP/1.1</code> or <code>AJP/1.3</code> then if this attribute is
        <code>true</code> the APR/native connector will be used but if this
        attribute is false the NIO connector will be used.</p>
      </attribute>

      <attribute name="useOpenSSL" required="false">
        <p>This attribute controls the auto-selection of the OpenSSL JSSE
        implementation. The default is <code>true</code> which will use OpenSSL
        if the native library is available and a NIO or NIO2 connector is used.</p>
      </attribute>

    </attributes>

  </subsection>

  <subsection name="Global Resources Lifecycle Listener - org.apache.catalina.mbeans.GlobalResourcesLifecycleListener">

    <p>The <strong>Global Resources Lifecycle Listener</strong> initializes the
    Global JNDI resources defined in server.xml as part of the <a
    href="globalresources.html">Global Resources</a> element. Without this
    listener, none of the Global Resources will be available.</p>

    <p>This listener must only be nested within <a href="server.html">Server</a>
    elements.</p>

    <p>No additional attributes are supported by the <strong>Global Resources
    Lifecycle Listener</strong>.</p>

  </subsection>

  <subsection name="JNI Library Loading Listener - org.apache.catalina.core.JniLifecycleListener">

    <p>The <strong>JNI Library Loading Listener</strong> makes it possible
    for multiple Webapps to use a native library, by loading the native
    library using a shared class loader (typically the Common class loader but
    may vary in some configurations)</p>

    <p>The listener supports two mutually exclusive attributes, so one of them must be used, but you can not use both together:</p>

    <attributes>
      <attribute name="libraryName" required="false">
        <p>The name of the native library, as defined in
        <code>java.lang.System.loadLibrary()</code>
        </p>
      </attribute>
      <attribute name="libraryPath" required="false">
        <p>The absolute path of the native library, as defined in
        <code>java.lang.System.load()</code>
        </p>
      </attribute>
    </attributes>
  </subsection>

  <subsection name="JRE Memory Leak Prevention Listener - org.apache.catalina.core.JreMemoryLeakPreventionListener">

    <p>The <strong>JRE Memory Leak Prevention Listener</strong> 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.</p>

    <p>This listener must only be nested within <a href="server.html">Server</a>
    elements.</p>

    <p>The following additional attributes are supported by the <strong>JRE
    Memory Leak Prevention Listener</strong>:</p>

    <attributes>

      <attribute name="appContextProtection" required="false">
        <p>Enables protection so that calls to
        <code>sun.awt.AppContext.getAppContext()</code> triggered by a web
        application do not result in a memory leak. Note that enabling this
        protection will trigger a requirement for a graphical environment unless
        Java is started in head-less mode. The default is <code>false</code>.
        This protection is disabled if running on Java 8 onwards since the leak
        has been fixed for Java 8 onwards.
        </p>
      </attribute>

      <attribute name="AWTThreadProtection" required="false">
        <p>Enables protection so that calls to
        <code>java.awt.Toolkit.getDefaultToolkit()</code> triggered by a web
        application do not result in a memory leak.
        Defaults to <code>false</code> because an AWT thread is launched. This
        protection is disabled if running on Java 9 onwards since the leak has
        been fixed for Java 9 onwards.</p>
      </attribute>

      <attribute name="classesToInitialize" required="false">
        <p>List of comma-separated fully qualified class names to load and initialize
        during the startup of this Listener. This allows to pre-load classes that are
        known to provoke classloader leaks if they are loaded during a request
        processing. Non-JRE classes may be referenced, like
        <code>oracle.jdbc.driver.OracleTimeoutThreadPerVM</code>.
        The default value is empty, but specific JRE classes are loaded by other leak
        protection features managed by other attributes of this Listener.</p>
      </attribute>

      <attribute name="driverManagerProtection" required="false">
        <p>The first use of <code>java.sql.DriverManager</code> will trigger the
        loading of JDBC Drivers visible to the current class loader and its
        parents. The web application level memory leak protection can take care
        of this in most cases but triggering the loading here has fewer
        side-effects. The default is <code>true</code>.</p>
      </attribute>

      <attribute name="forkJoinCommonPoolProtection" required="false">
        <p>Enables protection so the threads created for
        <code>ForkJoinPool.commonPool()</code> do not result in a memory leak.
        The protection is enabled by setting the
        <code>java.util.concurrent.ForkJoinPool.common.threadFactory</code>
        system property. If this property is set when Tomcat starts, Tomcat will
        not over-ride it even if this protection is explicitly enabled. The
        default is <code>true</code>. This protection is only used when running
        on Java 8. The common pool does not exist in earlier versions and the
        leak has been fixed for Java 9 onwards.</p>
      </attribute>

      <attribute name="gcDaemonProtection" required="false">
        <p>Enables protection so that calls to
        <code>sun.misc.GC.requestLatency(long)</code> 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 uses
        reflection to access internal Sun classes and may generate errors on
        startup on non-Sun JVMs. The default is <code>true</code>. This
        protection is disabled if running on Java 9 onwards since the leak has
        been fixed for Java 9 onwards.</p>
      </attribute>

      <attribute name="ldapPoolProtection" required="false">
        <p>Enables protection so that the PoolCleaner thread started by
        <code>com.sun.jndi.ldap.LdapPoolManager</code> does not result in a
        memory leak. The thread is started the first time the
        <code>LdapPoolManager</code> class is used if the system property
        <code>com.sun.jndi.ldap.connect.pool.timeout</code> is set to a value
        greater than 0. Without this protection, if a web application uses this
        class the PoolCleaner thread will be configured with the thread's
        context class loader set to the web application class loader which in
        turn will trigger a memory leak on reload. Defaults to
        <code>true</code>. This protection is disabled if running on Java 9
        onwards since the leak has been fixed for Java 9 onwards.</p>
      </attribute>

      <attribute name="securityLoginConfigurationProtection" required="false">
        <p>Enables protection so that usage of the
        <code>javax.security.auth.login.Configuration</code> class by a web
        application does not provoke a memory leak. The first access of this
        class will trigger the initializer that will retain a static reference
        to the context class loader. The protection loads the class with the
        system class loader to ensure that the static initializer is not
        triggered by a web application. Defaults to <code>true</code>. This
        protection is disabled if running on Java 8 onwards since the leak has
        been fixed for Java 8 onwards.</p>
      </attribute>

      <attribute name="securityPolicyProtection" required="false">
        <p>Enables protection so that usage of the deprecated
        <code>javax.security.auth.Policy</code> class by a web application does
        not result in a memory leak. The first access of this class will trigger
        the static initializer that will retain a static reference to the
        context class loader. The protection calls the <code>getPolicy()</code>
        method of this class to ensure that the static initializer is not
        triggered by a web application. Defaults to <code>true</code>.</p>
        <p>Note: The underlying leak has been fixed in Java 7 update 51 onwards
        and Java 8 onwards. This protection is therefore disabled if running on
        Java 8 onwards.</p>
      </attribute>

      <attribute name="tokenPollerProtection" required="false">
        <p>Enables protection so that any token poller thread initialized by
        <code>sun.security.pkcs11.SunPKCS11.initToken()</code> does not
        result in a memory leak. The thread is started depending on various
        conditions as part of the initialization of the Java Cryptography
        Architecture. Without the protection this can happen during Webapp
        deployment when the MessageDigest for generating session IDs is
        initialized. As a result the thread has the Webapp class loader as its
        thread context class loader. Enabling the protection initializes JCA
        early during Tomcat startup. Defaults to <code>true</code>. This
        protection is disabled if running on Java 9 onwards since the leak has
        been fixed for Java 9 onwards.</p>
      </attribute>

      <attribute name="urlCacheProtection" required="false">
        <p>Enables protection so that reading resources from JAR files using
        <code>java.net.URLConnection</code>s does not result in the JAR file
        being locked. Note that enabling this protection disables caching by
        default for all resources obtained via
        <code>java.net.URLConnection</code>s. Caching may be re-enabled on a
        case by case basis as required. Defaults to <code>true</code>.</p>
      </attribute>

      <attribute name="xmlParsingProtection" required="false">
        <p>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 <code>true</code>. This protection is
        disabled if running on Java 9 onwards since the leak has been fixed for
        Java 9 onwards.</p>
      </attribute>

    </attributes>

    <subsection name="JreMemoryLeakPreventionListener Examples">

      <p>The following is an example of how to configure the
      <code>classesToInitialize</code> attribute of this listener.</p>

      <p>If this listener was configured in server.xml as:</p>

      <source><![CDATA[  <Listener className="org.apache.catalina.core.JreMemoryLeakPreventionListener"
            classesToInitialize="oracle.jdbc.driver.OracleTimeoutThreadPerVM" />]]></source>

      <p>then the <code>OracleTimeoutThreadPerVM</code> class would be loaded
      and initialized during listener startup instead of during request
      processing.</p>

    </subsection>

  </subsection>

  <subsection name="Security Lifecycle Listener - org.apache.catalina.security.SecurityListener">

    <p>The <strong>Security Lifecycle Listener</strong> performs a number of
    security checks when Tomcat starts and prevents Tomcat from starting if they
    fail. The listener is not enabled by default. To enabled it uncomment the
    listener in $CATALINA_BASE/conf/server.xml. For Tomcat versions before 8.5.30,
    if the operating system supports umask then the line in
    $CATALINA_HOME/bin/catalina.sh that obtains the umask also needs to be
    uncommented. For Tomcat 8.5.30 and later, the umask is automatically
    passed-into Tomcat.</p>

    <p>This listener must only be nested within <a href="server.html">Server</a>
    elements.</p>

    <p>The following additional attributes are supported by the <strong>Security
    Lifecycle Listener</strong>:</p>

    <attributes>

      <attribute name="checkedOsUsers" required="false">
        <p>A comma separated list of OS users that must not be used to start
        Tomcat. If not specified, the default value of <b>root</b> is used. To
        disable this check, set the attribute to the empty string. Usernames
        are checked in a case-insensitive manner.</p>
      </attribute>

      <attribute name="minimumUmask" required="false">
        <p>The least restrictive umask that must be configured before Tomcat
        will start. If not specified, the default value of <b>0007</b> is used.
        To disable this check, set the attribute to the empty string. The check
        is not performed on Windows platforms.</p>
      </attribute>

    </attributes>

  </subsection>

  <subsection name="StoreConfig Lifecycle Listener - org.apache.catalina.storeconfig.StoreConfigLifecycleListener">

    <p>The <strong>StoreConfig Lifecycle Listener</strong> configures a
    StoreConfig MBean that may be used to save the current server configuration
    in server.xml or the current configuration for a web application in a
    context.xml file.</p>

    <p>This listener must only be nested within <a href="server.html">Server</a>
    elements.</p>

    <p>The following additional attributes are supported by the
    <strong>StoreConfig Lifecycle Listener</strong>:</p>

    <attributes>

      <attribute name="storeConfigClass" required="false">
        <p>The name of the <code>IStoreConfig</code> implementation to use. If
        not specified the default of
        <code>org.apache.catalina.storeconfig.StoreConfig</code> will be
        used.</p>
      </attribute>

      <attribute name="storeRegistry" required="false">
        <p>The URL of the configuration file that configures how the
        <code>IStoreConfig</code> is to save the configuration. If not specified
        the built in resource
        <code>/org/apache/catalina/storeconfig/server-registry.xml</code> will
        be used.</p>
      </attribute>

    </attributes>

  </subsection>

  <subsection name="ThreadLocal Leak Prevention Listener - org.apache.catalina.core.ThreadLocalLeakPreventionListener">

    <p>The <strong>ThreadLocal Leak Prevention Listener</strong> triggers the
    renewal of threads in <a href="executor.html">Executor</a> pools when a
    <a href="context.html">Context</a> is being stopped to avoid thread-local
    related memory leaks. Active threads will be renewed one by one when they
    come back to the pool after executing their task. The renewal happens
    only for contexts that have their <code>renewThreadsWhenStoppingContext</code>
    attribute set to <code>true</code>.</p>

    <p>This listener must only be nested within <a href="server.html">Server</a>
    elements.</p>

    <p>No additional attributes are supported by the <strong>ThreadLocal Leak
    Prevention Listener</strong>.</p>

  </subsection>

  <subsection name="UserConfig - org.apache.catalina.startup.UserConfig">

    <p>The <strong>UserConfig</strong> provides feature of User Web Applications.
    User Web Applications map a request URI starting with a tilde character ("~")
    and a username to a directory (commonly named public_html) in that user's
    home directory on the server.</p>

    <p>See the <a href="host.html#User_Web_Applications">User Web Applications</a>
    special feature on the <strong>Host</strong> element for more information.</p>

    <p>The following additional attributes are supported by the
    <strong>UserConfig</strong>:</p>

    <attributes>

      <attribute name="directoryName" required="false">
        <p>The directory name to be searched for within each user home directory.
        The default is <code>public_html</code>.</p>
      </attribute>

      <attribute name="userClass" required="false">
        <p>The class name of the user database class.
        There are currently two user database, the
        <code>org.apache.catalina.startup.PasswdUserDatabase</code> is used on a
        Unix system that uses the /etc/passwd file to identify valid users.
        The <code>org.apache.catalina.startup.HomesUserDatabase</code> is used on
        a server where /etc/passwd is not in use. HomesUserDatabase deploy all
        directories found in a specified base directory.</p>
      </attribute>

      <attribute name="homeBase" required="false">
        <p>The base directory containing user home directories. This is effective
        only when <code>org.apache.catalina.startup.HomesUserDatabase</code> is
        used.</p>
      </attribute>

      <attribute name="allow" required="false">
        <p>A regular expression defining user who deployment is allowed. If this
        attribute is specified, the user to deploy must match for this pattern.
        If this attribute is not specified, all users will be deployed unless the
        user matches a deny pattern.</p>
      </attribute>

      <attribute name="deny" required="false">
        <p>A regular expression defining user who deployment is denied. If this
        attribute is specified, the user to deploy must not match for this
        pattern. If this attribute is not specified, deployment of user will be
        governed by a allow attribute.</p>
      </attribute>

    </attributes>

  </subsection>

  <subsection name="Version Logging Lifecycle Listener - org.apache.catalina.startup.VersionLoggerListener">

    <p>The <strong>Version Logging Lifecycle Listener</strong> logs Tomcat, Java
    and operating system information when Tomcat starts.</p>

    <p>This listener must only be nested within <a href="server.html">Server</a>
    elements and should be the first listener defined.</p>

    <p>The following additional attributes are supported by the <strong>Version
    Logging Lifecycle Listener</strong>:</p>

    <attributes>

      <attribute name="logArgs" required="false">
        <p>If <code>true</code>, the command line arguments passed to Java when
        Tomcat started will be logged. If not specified, the default value of
        <code>true</code> will be used.</p>
      </attribute>

      <attribute name="logEnv" required="false">
        <p>If <code>true</code>, the current environment variables when Tomcat
        starts will be logged. If not specified, the default value of
        <code>false</code> will be used.</p>
      </attribute>

      <attribute name="logProps" required="false">
        <p>If <code>true</code>, the current Java system properties will be
        logged. If not specified, the default value of
        <code>false</code> will be used.</p>
      </attribute>

    </attributes>

  </subsection>

</section>

<section name="Additional Implementations">

  <subsection name="System property replacement - org.apache.catalina.util.SystemPropertyReplacerListener">

    <p>This listener performs system property replacement using the property
     source configured on the digester. When <code>${parameter}</code>
     denoted parameters are found in the values of system properties,
     the property source will be invoked to attempt to replace it.</p>

  </subsection>

</section>

</body>

</document>
