读懂tomact源码4:Container

Container的解释

 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.

event type

    /**     * 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().     * @deprecated Unused. Will be removed in Tomcat 8.0.x.     */    @Deprecated    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().     * @deprecated Unused. Will be removed in Tomcat 8.0.x.     */    @Deprecated    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 <code>null</code>.     */    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 <code>null</code>.     */    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 <code>null</code>.     */    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.     */    @Deprecated    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 <code>null</code>.     */    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 <code>null</code>.     */    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 for this component. If not set, return     * {@link #getParent()} {@link #getParentClassLoader()}. If no parent has     * been set, return the system class loader.     */    public ClassLoader getParentClassLoader();    /**     * Set the parent class loader for this component. For {@link Context}s     * this call is meaningful only <strong>before</strong> 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 <code>null</code>.     */    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 <code>null</code>.     */    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 <code>setParent()</code> method must be called, with this     * Container as an argument.  This method may thrown an     * <code>IllegalArgumentException</code> 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 <code>setParent()</code> 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 <code>null</code>     *     * @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     *     * @deprecated Unused. Will be removed in Tomcat 8.0.x.     */    @Deprecated    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();    /**     * Returns the number of threads available for starting and stopping any     * children associated with this container. This allows start/stop calls to     * children to be processed in parallel.     */    public int getStartStopThreads();    /**     * Sets the number of threads available for starting and stopping any     * children associated with this container. This allows start/stop calls to     * children to be processed in parallel.     * @param   startStopThreads    The new number of threads to be used     */    public void setStartStopThreads(int startStopThreads);

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.
  代表完整的Servlet引擎，是最顶层的容器，在这个容器上调用setParent会抛出异常。一个Engine由多个Host容器组成
  
• Host - Representation of a virtual host containing a number of Contexts.
  代表一个虚拟主机，可以运行多个应用，它负责安装和展开这些应用，其子容器为Context
  
• Context - Representation of a single ServletContext, which will typically contain one or more Wrappers for the supported servlets.
  :代表ServletContext，管理多个Servlet，理论上只要有Context就可以运行Servlet了，其子容器为Wrapper
  
• Wrapper - Representation of an individual servlet definition (which may support multiple servlet instances if the servlet itself implements SingleThreadModel).
  

代表一个Servlet，是最底部的容器，它没有子容器。它负责管理一个Servlet，包含Servlet的装载、初始化、执行和卸载等。只有Wrapper也是可以运行Servlet
类的继承关系如下：

components:Loader，Logger，Manager，Realm，Resources

• 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.

*