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/*
* LeaseManager.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>LeaseManager</code> is used to issue a lease for a
* named resource. This is effectively used to issue a request
* for a keyed resource to be released when a lease has expired.
* The use of a <code>Lease</code> simplifies the interface to
* the notification and also enables other objects to manage the
* lease without any knowledge of the resource it represents.
*
* @author Niall Gallagher
*/
public class LeaseManager<T> implements LeaseProvider<T> {
/**
* This is the controller used to handle lease operations.
*/
private ContractController<T> handler;
/**
* Constructor for the <code>LeaseManager</code> object. This
* instance is created using a specified notification handler.
* The specified <code>Cleaner</code> will be notified when
* the lease for a named resource expires, which will allow
* the cleaner object to perform a clean up for that resource.
*
* @param cleaner the cleaner object receiving notifications
*/
public LeaseManager(Cleaner<T> cleaner) {
this.handler = new ContractMaintainer<T>(cleaner);
}
/**
* This method will issue a <code>Lease</code> object that
* can be used to manage the release of a keyed resource. If
* the lease duration expires before it is renewed then the
* notification is sent, typically to a <code>Cleaner</code>
* implementation, to signify that the resource should be
* recovered. The issued lease can also be canceled.
*
* @param key this is the key for the leased resource
* @param duration this is the duration of the issued lease
* @param unit this is the time unit to issue the lease with
*
* @return a lease that can be used to manage notification
*/
public Lease<T> lease(T key, long duration, TimeUnit unit) {
Contract<T> contract = new Expiration<T>(key, duration, unit);
try {
handler.issue(contract);
} catch(Exception e) {
throw new LeaseException("Could not issue lease", e);
}
return new ContractLease<T>(handler, contract);
}
/**
* This is used to close the lease provider such that all of
* the outstanding leases are canceled. This also ensures the
* provider can no longer be used to issue new leases, such
* that further invocations of the <code>lease</code> method
* will result in null leases. Once the provider has been
* closes all threads and other such resources are released.
*/
public void close() {
try {
handler.close();
} catch(Exception e) {
return;
}
}
}
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