org.apache.catalina.Lifecycle Maven / Gradle / Ivy
/*
* 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.
*/
package org.apache.catalina;
/**
* Common interface for component life cycle methods. Catalina components
* may implement this interface (as well as the appropriate interface(s) for
* the functionality they support) in order to provide a consistent mechanism
* to start and stop the component.
*
* The valid state transitions for components that support Lifecycle are:
*
* --------------------<-----------------------
* | |
* init() start() | auto auto stop() |
* NEW ->-- INITIALIZED -->-- STARTING_PREP -->- STARTING -->- STARTED -->--- |
* ||| ^ | | |
* ||| start() | | | |
* ||----------->-------------------- | | |
* || | | |
* |--- auto auto | | |
* | | ---------<----- MUST_STOP ---------------------<-- | |
* | | | | |
* | | ---------------------------<-------------------------------- ^
* | | | |
* | | | auto auto start() |
* | | STOPPING_PREP ------>----- STOPPING ------>----- STOPPED ---->------
* | | ^ | | ^
* | | | auto | | |
* | | |stop() MUST_DESTROY------<------- | |
* | | | | | |
* | | | |auto | |
* | | | destroy() \|/ destroy() | |
* | | FAILED ---->------ DESTROYED ----<----------------- |
* | | ^ |
* | | destroy() | |
* | ------------------------------- |
* | |
* | stop() |
* --->------------------------------>------------------------------
*
* Any state can transition to FAILED.
*
* Calling start() while a component is in states STARTING_PREP, STARTING or
* STARTED has no effect.
*
* Calling start() while a component is in state NEW will cause init() to be
* called immediately after the start() method is entered.
*
* Calling stop() while a component is in states STOPPING_PREP, STOPPING or
* STOPPED has no effect.
*
* Calling stop() while a component is in state NEW transitions the component
* to STOPPED. This is typically encountered when a component fails to start and
* does not start all its sub-components. When the component is stopped, it will
* try to stop all sub-components - even those it didn't start.
*
* MUST_STOP is used to indicate that the {@link #stop()} should be called on
* the component as soon as {@link #start()} exits. It is typically used when a
* component has failed to start.
*
* MUST_DESTROY is used to indicate that the {@link #stop()} should be called on
* the component as soon as {@link #stop()} exits. It is typically used when a
* component is not designed to be restarted.
*
* Attempting any other transition will throw {@link LifecycleException}.
*
*
* The {@link LifecycleEvent}s fired during state changes are defined in the
* methods that trigger the changed. No {@link LifecycleEvent}s are fired if the
* attempted transition is not valid.
*
* TODO: Not all components may transition from STOPPED to STARTING_PREP
*
* @author Craig R. McClanahan
* @version $Id: Lifecycle.java 942794 2010-05-10 15:41:58Z markt $
*/
public interface Lifecycle {
// ----------------------------------------------------- Manifest Constants
/**
* The LifecycleEvent type for the "component init" event.
*/
public static final String INIT_EVENT = "init";
/**
* The LifecycleEvent type for the "component start" event.
*/
public static final String START_EVENT = "start";
/**
* The LifecycleEvent type for the "component before start" event.
*/
public static final String BEFORE_START_EVENT = "before_start";
/**
* The LifecycleEvent type for the "component after start" event.
*/
public static final String AFTER_START_EVENT = "after_start";
/**
* The LifecycleEvent type for the "component stop" event.
*/
public static final String STOP_EVENT = "stop";
/**
* The LifecycleEvent type for the "component before stop" event.
*/
public static final String BEFORE_STOP_EVENT = "before_stop";
/**
* The LifecycleEvent type for the "component after stop" event.
*/
public static final String AFTER_STOP_EVENT = "after_stop";
/**
* The LifecycleEvent type for the "component destroy" event.
*/
public static final String DESTROY_EVENT = "destroy";
/**
* The LifecycleEvent type for the "periodic" event.
*/
public static final String PERIODIC_EVENT = "periodic";
/**
* The LifecycleEvent type for the "configure_start" event. Used by those
* components that use a separate component to perform configuration and
* need to signal when configuration should be performed - usually after
* {@link #BEFORE_START_EVENT} and before {@link #START_EVENT}.
*/
public static final String CONFIGURE_START_EVENT = "configure_start";
/**
* The LifecycleEvent type for the "configure_stop" event. Used by those
* components that use a separate component to perform configuration and
* need to signal when de-configuration should be performed - usually after
* {@link #STOP_EVENT} and before {@link #AFTER_STOP_EVENT}.
*/
public static final String CONFIGURE_STOP_EVENT = "configure_stop";
// --------------------------------------------------------- Public Methods
/**
* Add a LifecycleEvent listener to this component.
*
* @param listener The listener to add
*/
public void addLifecycleListener(LifecycleListener listener);
/**
* Get the lifecycle listeners associated with this lifecycle. If this
* Lifecycle has no listeners registered, a zero-length array is returned.
*/
public LifecycleListener[] findLifecycleListeners();
/**
* Remove a LifecycleEvent listener from this component.
*
* @param listener The listener to remove
*/
public void removeLifecycleListener(LifecycleListener listener);
/**
* Prepare the component for starting. This method should perform any
* initialization required post object creation. The following
* {@link LifecycleEvent}s will be fired in the following order:
*
* - INIT_EVENT: On the successful completion of component
* initialization.
*
*
* @exception LifecycleException if this component detects a fatal error
* that prevents this component from being used
*/
public void init() throws LifecycleException;
/**
* Prepare for the beginning of active use of the public methods of this
* component. This method should be called before any of the public
* methods of this component are utilized. The following
* {@link LifecycleEvent}s will be fired in the following order:
*
* - BEFORE_START_EVENT: At the beginning of the method. It is as this
* point the state transitions to
* {@link LifecycleState#STARTING_PREP}.
* - START_EVENT: During the method once it is safe to call start() for
* any child components. It is at this point that the
* state transitions to {@link LifecycleState#STARTING}
* and that the public methods may be used.
* - AFTER_START_EVENT: At the end of the method, immediately before it
* returns. It is at this point that the state
* transitions to {@link LifecycleState#STARTED}.
*
*
*
* @exception LifecycleException if this component detects a fatal error
* that prevents this component from being used
*/
public void start() throws LifecycleException;
/**
* Gracefully terminate the active use of the public methods of this
* component. Once the STOP_EVENT is fired, the public methods should not
* be used. The following {@link LifecycleEvent}s will be fired in the
* following order:
*
* - BEFORE_STOP_EVENT: At the beginning of the method. It is at this
* point that the state transitions to
* {@link LifecycleState#STOPPING_PREP}.
* - STOP_EVENT: During the method once it is safe to call stop() for
* any child components. It is at this point that the
* state transitions to {@link LifecycleState#STOPPING}
* and that the public methods may no longer be used.
* - AFTER_STOP_EVENT: At the end of the method, immediately before it
* returns. It is at this point that the state
* transitions to {@link LifecycleState#STOPPED}.
*
*
*
* @exception LifecycleException if this component detects a fatal error
* that needs to be reported
*/
public void stop() throws LifecycleException;
/**
* Prepare to discard the object. The following {@link LifecycleEvent}s will
* be fired in the following order:
*
* - DESTROY_EVENT: On the successful completion of component
* destruction.
*
*
* @exception LifecycleException if this component detects a fatal error
* that prevents this component from being used
*/
public void destroy() throws LifecycleException;
/**
* Obtain the current state of the source component.
*
* @return The current state of the source component.
*/
public LifecycleState getState();
}