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	/*
	* Copyright (c) 2004, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package sun.jvmstat.monitor;

	import java.util.List;

	import sun.jvmstat.monitor.event.VmListener;

	/**
	* Interface for interacting with a monitorable Java Virtual Machine.
	* The MonitoredVm interface provides methods for discovery of exported
	* instrumentation, for attaching event listeners, and for overall
	* maintenance of the connection to the target.
	*
	* @author Brian Doherty
	* @since 1.5
	*/
	public interface MonitoredVm {

	/**
	* Get the VmIdentifier associated with this MonitoredVm
	*
	* @return VmIdentifier - the fully resolved Vm identifier associated
	* with this MonitoredVm.
	*/
	VmIdentifier getVmIdentifier();

	/**
	* Find a named Instrumentation object.
	*
	* This method will look for the named instrumentation object in the
	* instrumentation exported by this Java Virtual Machine. If an
	* instrumentation object with the given name exists, a Monitor interface
	* to that object will be return. Otherwise, the method returns
	* <tt>null</tt>.
	*
	* @param name the name of the Instrumentation object to find.
	* @return Monitor - the {@link Monitor} object that can be used to
	* monitor the the named instrumentation object, or
	* <tt>null</tt> if the named object doesn't exist.
	* @throws MonitorException Thrown if an error occurs while communicating
	* with the target Java Virtual Machine.
	*/
	Monitor findByName(String name) throws MonitorException;

	/**
	* Find all Instrumentation objects with names matching the given pattern.
	*
	* This method returns a {@link List} of Monitor objects such that
	* the name of each object matches the given pattern.
	*
	* @param patternString a string containing a pattern as described in
	* {@link java.util.regex.Pattern}.
	* @return List<Monitor> - a List of {@link Monitor} objects that can be used to
	* monitor the instrumentation objects whose names match
	* the given pattern. If no instrumentation objects have`
	* names matching the given pattern, then an empty List
	* is returned.
	* @throws MonitorException Thrown if an error occurs while communicating
	* with the target Java Virtual Machine.
	* @see java.util.regex.Pattern
	*/
	List<Monitor> findByPattern(String patternString) throws MonitorException;

	/**
	* Detach from target Java Virtual Machine.
	*
	* After calling this method, updates of the instrumentation data values
	* may be halted. All event notifications are halted. Further interactions
	* with this object should be avoided.
	*/
	void detach();


	/* ---- Methods to support polled MonitoredVm Implementations ---- */

	/**
	* Set the polling interval to <code>interval</code> milliseconds.
	*
	* Polling based monitoring implementations need to refresh the
	* instrumentation data on a periodic basis. This interface allows
	* the interval to override the implementation specific default
	* interval.
	*
	* @param interval the polling interval in milliseconds
	*/
	void setInterval(int interval);

	/**
	* Get the polling interval.
	*
	* @return int - the current polling interval in milliseconds.
	* @see #setInterval
	*/
	int getInterval();

	/**
	* Set the last exception encountered while polling this MonitoredVm.
	*
	* Polling implementations may choose to poll asynchronously. This
	* method allows an asynchronous task to communicate any polling related
	* exceptions with the application. When an a non-null exception is reported
	* through this interface, the MonitoredVm instance is considered to
	* be in the <em>errored</em> state.
	*
	* @param cause the exception to record.
	* @see #isErrored
	*/
	void setLastException(Exception cause);

	/**
	* Get the last exception encountered while polling this MonitoredVm.
	*
	* Returns the last exception observed by the implementation dependent
	* polling task or <tt>null</tt> if no such error has occurred.
	*
	* @return Exception - the last exception that occurred during polling
	* or <tt>null</tt> if no error condition exists.
	* @see #isErrored
	* @see #setLastException
	*/
	Exception getLastException();

	/**
	* Clear the last exception.
	*
	* Calling this method will clear the <em>errored</em> state of this
	* MonitoredVm. However, there is no guarantee that clearing the
	* the errored state return the asynchronous polling task to an
	* operational state.
	*
	*/
	void clearLastException();

	/**
	* Test if this MonitoredVm is in the errored state.
	* The errored state exists only if an error was reported with
	* call to {@link #setLastException} and only if the parameter to
	* that call was non-null and no subsequent calls are made to
	* {@link #clearLastException}.
	*
	* @return boolean - true if the instance has a non-null error condition
	* set, false otherwise.
	*
	* @see #setLastException
	* @see #getLastException
	*/
	boolean isErrored();

	/**
	* Add a VmListener. The given listener is added to the list of
	* VmListener objects to be notified of MonitoredVm related events.
	*
	* @param listener the VmListener to add.
	* @throws MonitorException Thrown if any problems occur while attempting
	* to add this listener.
	*/
	void addVmListener(VmListener listener) throws MonitorException;

	/**
	* Remove a VmListener. The given listener is removed from the list of
	* VmListener objects to be notified of MonitoredVm related events.
	*
	* @param listener the VmListener to be removed.
	* @throws MonitorException Thrown if any problems occur while attempting
	* to remove this listener.
	*/
	void removeVmListener(VmListener listener) throws MonitorException;
	}

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