读懂tomact源码4:Container

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Container的解释

 A Container is an object that can execute requests received froma client, and return responses based on those requests.  A Container mayoptionally support a pipeline of Valves that process the request in anorder configured at runtime, by implementing the Pipeline　interfaceas 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.*/@Deprecatedpublic 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.*/@Deprecatedpublic 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.*/@Deprecatedpublic 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.*/@Deprecatedpublic 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).