| /* |
| * Lease.java May 2004 |
| * |
| * Copyright (C) 2004, Niall Gallagher <niallg@users.sf.net> |
| * |
| * Licensed 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.simpleframework.common.lease; |
| |
| import java.util.concurrent.TimeUnit; |
| |
| /** |
| * The <code>Lease</code> object is used to keep a keyed resource |
| * active. This provides a very simple lease that can be used to |
| * track the activity of a resource or system. Keeping track of |
| * activity allows resources to be maintained until such time |
| * that they are no longer required, allowing the server to clean |
| * up any allocated memory, file descriptors, or other such data. |
| * |
| * @author Niall Gallagher |
| */ |
| public interface Lease<T> { |
| |
| /** |
| * Determines the duration remaining before the lease expires. |
| * The expiry is given as the number of <code>TimeUnit</code> |
| * seconds remaining before the lease expires. If this value is |
| * negative it should be assumed that the lease has expired. |
| * |
| * @param unit this is the time unit used for the duration |
| * |
| * @return the duration remaining within this lease instance |
| * |
| * @exception Exception if the expiry could not be acquired |
| */ |
| long getExpiry(TimeUnit unit) throws LeaseException; |
| |
| /** |
| * This ensures that the leased resource is maintained for the |
| * specified number of <code>TimeUnit</code> seconds. Allowing |
| * the duration unit to be specified enables the lease system |
| * to maintain a resource with a high degree of accuracy. The |
| * accuracy of the leasing system is dependent on how long it |
| * takes to clean the resource associated with the lease. |
| * |
| * @param duration this is the length of time to renew for |
| * @param unit this is the time unit used for the duration |
| * |
| * @exception Exception if the lease could not be renewed |
| */ |
| void renew(long duration, TimeUnit unit) throws LeaseException; |
| |
| /** |
| * This will cancel the lease and release the resource. This |
| * has the same effect as the <code>renew</code> method with |
| * a zero length duration. Once this has been called the |
| * <code>Cleaner</code> used should be notified immediately. |
| * If the lease has already expired this throws an exception. |
| * |
| * @exception Exception if the expiry has been passed |
| */ |
| void cancel() throws LeaseException; |
| |
| /** |
| * Provides the key for the resource that this lease represents. |
| * This can be used to identify the resource should the need |
| * arise. Also, this provides a convenient means of identifying |
| * leases when using or storing it as an <code>Object</code>. |
| * |
| * @return this returns the key for the resource represented |
| */ |
| T getKey(); |
| |
| } |