Tomcat(8-1) Container Interface

Container interface source code who is excerpted from Tomcat V7.

/*
* 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;

import java.beans.PropertyChangeListener;
import java.io.IOException;

import javax.management.ObjectName;
import javax.naming.directory.DirContext;
import javax.servlet.ServletException;

import org.apache.catalina.connector.Request;
import org.apache.catalina.connector.Response;
import org.apache.juli.logging.Log;

/**
* A Container is an object that can execute requests received from a client, and return responses based on those requests. 
* A Container may optionally support a pipeline of Valves that process the request in an order configured at runtime,
* by implementing the Pipeline interface as well.
* Containers will exist at several conceptual levels within Catalina.  The following examples represent common cases:
* Engine - Representation of the entire Catalina servlet engine, most likely containing one or more
* subcontainers that are either Host or Context implementations, or other custom groups.
* Host - Representation of a virtual host containing a number of Contexts.
* Context - Representation of a single ServletContext, which will typically contain one or more Wrappers for the supported servlets.
* Wrapper - Representation of an individual servlet definition (which may support multiple servlet instances
* if the servlet itself implements SingleThreadModel).
* A given deployment of Catalina need not include Containers at all of the levels described above. 
* For example, an administration application embedded within a network device (such as a router) might only  contain a single Context and
* a few Wrappers, or even a single Wrapper if the application is relatively small.  Therefore, Container implementations need to be designed
* so that they will operate correctly in the absence of parent Containers in a given deployment.
* A Container may also be associated with a number of support components that provide functionality which might be shared
* (by attaching it to a parent Container) or individually customized.  The following support components are currently recognized:
* Loader - Class loader to use for integrating new Java classes for this Container into the JVM in which Catalina is running.
* Logger - Implementation of the log() method signatures of the ServletContext interface.
* Manager - Manager for the pool of Sessions associated with this Container.
* Realm - Read-only interface to a security domain, for authenticating user identities and their corresponding roles.
* Resources - JNDI directory context enabling access to static resources, enabling custom linkages to existing server components
* when Catalina is embedded in a larger server.
*
* @author Craig R. McClanahan
* @author Remy Maucherat
* @version $Id: Container.java 987920 2010-08-22 15:34:34Z markt $
*/

public interface Container extends Lifecycle {

    // ----------------------------------------------------- Manifest Constants

    /**
     * The ContainerEvent event type sent when a child container is added by addChild().
     */
    public static final String ADD_CHILD_EVENT = "addChild";

    /**
     * The ContainerEvent event type sent when a Mapper is added by addMapper().
     */
    public static final String ADD_MAPPER_EVENT = "addMapper";

    /**
     * The ContainerEvent event type sent when a valve is added by addValve(), if this Container supports pipelines.
     */
    public static final String ADD_VALVE_EVENT = "addValve";

    /**
     * The ContainerEvent event type sent when a child container is removed by removeChild().
     */
    public static final String REMOVE_CHILD_EVENT = "removeChild";

    /**
     * The ContainerEvent event type sent when a Mapper is removed by removeMapper().
     */
    public static final String REMOVE_MAPPER_EVENT = "removeMapper";

    /**
     * The ContainerEvent event type sent when a valve is removed by removeValve(), if this Container supports pipelines.
     */
    public static final String REMOVE_VALVE_EVENT = "removeValve";

    // ------------------------------------------------------------- Properties

    /**
     * Return descriptive information about this Container implementation and the corresponding version number, in the format description, version.
     */
    public String getInfo();

    /**
     * Return the Loader with which this Container is associated.  If there is no associated Loader, return the Loader associated with our parent Container (if any); otherwise, return null.
     */
    public Loader getLoader();

    /**
     * Set the Loader with which this Container is associated.
     *
     * @param loader The newly associated loader
     */
    public void setLoader(Loader loader);

    /**
     * Return the Logger with which this Container is associated.  If there is no associated Logger, return the Logger associated with our parent Container (if any); otherwise return null.
     */
    public Log getLogger();

    /**
     * Return the Manager with which this Container is associated.  If there is no associated Manager, return the Manager associated with our parent Container (if any); otherwise return null.
     */
    public Manager getManager();

    /**
     * Set the Manager with which this Container is associated.
     *
     * @param manager The newly associated Manager
     */
    public void setManager(Manager manager);

    /**
     * Return an object which may be utilized for mapping to this component.
     */
    public Object getMappingObject();

    /**
     * Return the JMX name associated with this container.
     */
    public ObjectName getObjectName();   

    /**
     * Return the Pipeline object that manages the Valves associated with this Container.
     */
    public Pipeline getPipeline();

    /**
     * Return the Cluster with which this Container is associated.  If there is no associated Cluster, return the Cluster associated with our parent Container (if any); otherwise return null.
     */
    public Cluster getCluster();

    /**
     * Set the Cluster with which this Container is associated.
     *
     * @param cluster the Cluster with which this Container is associated.
     */
    public void setCluster(Cluster cluster);

    /**
     Get the delay between the invocation of the backgroundProcess method on this container and its children. Child containers will not be invoked if their delay value is not negative (which would mean they are using  their own thread). Setting this to a positive value will cause  a thread to be spawn. After waiting the specified amount of time, the thread will invoke the executePeriodic method on this container  and all its children.
     */
    public int getBackgroundProcessorDelay();

    /**
     * Set the delay between the invocation of the execute method on this container and its children.
     *
     * @param delay The delay in seconds between the invocation of backgroundProcess methods
     */
    public void setBackgroundProcessorDelay(int delay);

    /**
     Return a name string (suitable for use by humans) that describes this Container.  Within the set of child containers belonging to a particular parent, Container names must be unique.
     */
    public String getName();

    /**
     * Set a name string (suitable for use by humans) that describes this Container.  Within the set of child containers belonging to a particular parent, Container names must be unique.
     *
     * @param name New name of this container
     *
     * @exception IllegalStateException if this Container has already been added to the children of a parent Container (after which the name may not be changed)
     */
    public void setName(String name);

    /**
     * Return the Container for which this Container is a child, if there is one.  If there is no defined parent, return null.
     */
    public Container getParent();

    /**
     * Set the parent Container to which this Container is being added as a child.  This Container may refuse to become attached to the specified Container by throwing an exception.
     *
     * @param container Container to which this Container is being added as a child
     *
     * @exception IllegalArgumentException if this Container refuses to become attached to the specified Container
     */
    public void setParent(Container container);

    /**
     * Return the parent class loader (if any) for web applications.
     */
    public ClassLoader getParentClassLoader();

    /**
     Set the parent class loader (if any) for web applications. This call is meaningful only before a Loader has been configured, and the specified value (if non-null) should be passed as an argument to the class loader constructor.
     *
     * @param parent The new parent class loader
     */
    public void setParentClassLoader(ClassLoader parent);

    /**
     * Return the Realm with which this Container is associated.  If there is no associated Realm, return the Realm associated with our parent Container (if any); otherwise return null.
     */
    public Realm getRealm();

    /**
     * Set the Realm with which this Container is associated.
     *
     * @param realm The newly associated Realm
     */
    public void setRealm(Realm realm);

    /**
     Return the Resources with which this Container is associated.  If there is no associated Resources object, return the Resources associated with our parent Container (if any); otherwise return null.
     */
    public DirContext getResources();

    /**
     * Set the Resources object with which this Container is associated.
     *
     * @param resources The newly associated Resources
     */
    public void setResources(DirContext resources);

    // --------------------------------------------------------- Public Methods

    /**
     * Execute a periodic task, such as reloading, etc. This method will be invoked inside the classloading context of this container. Unexpected throwables will be caught and logged.
     */
    public void backgroundProcess();

    /**
     Add a new child Container to those associated with this Container, if supported.  Prior to adding this Container to the set of children, the child's setParent() method must be called, with this Container as an argument.  This method may thrown an IllegalArgumentException if this Container chooses not to be attached to the specified Container, in which case it is not added
     *
     * @param child New child Container to be added
     *
     * @exception IllegalArgumentException if this exception is thrown by  the setParent() method of the child Container
     * @exception IllegalArgumentException if the new child does not have a name unique from that of existing children of this Container
     * @exception IllegalStateException if this Container does not support  child Containers
     */
    public void addChild(Container child);

    /**
     * Add a container event listener to this component.
     *
     * @param listener The listener to add
     */
    public void addContainerListener(ContainerListener listener);

    /**
     * Add a property change listener to this component.
     *
     * @param listener The listener to add
     */
    public void addPropertyChangeListener(PropertyChangeListener listener);

    /**
     * Return the child Container, associated with this Container, with the specified name (if any); otherwise, return null
     *
     * @param name Name of the child Container to be retrieved
     */
    public Container findChild(String name);

    /**
     * Return the set of children Containers associated with this Container. If this Container has no children, a zero-length array is returned.
     */
    public Container[] findChildren();

    /**
     * Return the set of container listeners associated with this Container. If this Container has no registered container listeners, a zero-length array is returned.
     */
    public ContainerListener[] findContainerListeners();

    /**
     * Process the specified Request, and generate the corresponding Response, according to the design of this particular Container.
     *
     * @param request Request to be processed
     * @param response Response to be produced
     *
     * @exception IOException if an input/output error occurred while processing
     * @exception ServletException if a ServletException was thrown while processing this request
     */
    public void invoke(Request request, Response response) throws IOException, ServletException;

    /**
     * Remove an existing child Container from association with this parent Container.
     *
     * @param child Existing child Container to be removed
     */
    public void removeChild(Container child);

    /**
     * Remove a container event listener from this component.
     *
     * @param listener The listener to remove
     */
    public void removeContainerListener(ContainerListener listener);

    /**
     * Remove a property change listener from this component.
     *
     * @param listener The listener to remove
     */
    public void removePropertyChangeListener(PropertyChangeListener listener);

    /**
     Notify all container event listeners that a particular event has occurred for this Container.  The default implementation performs this notification synchronously using the calling thread.
     *
     * @param type Event type
     * @param data Event data
     */
    public void fireContainerEvent(String type, Object data);
    /**
     Log a request/response that was destined for this container but has been handled earlier in the processing chain so that the request/response still appears in the correct access logs.
     * @param request       Request (associated with the response) to log
     * @param response      Response (associated with the request) to log
     * @param time          Time taken to process the request/response in milliseconds (use 0 if not known)
     * @param   useDefault  Flag that indicates that the request/response should be logged in the engine's default access log
     */
    public void logAccess(Request request, Response response, long time, boolean useDefault);
    /**
     Identify the AccessLog to use to log a request/response that was destined for this container but was handled earlier in the processing chain so that the request/response still appears in the correct access logs.
     */
    public AccessLog getAccessLog();
}