/*
* ContractLease.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>ContractLease</code> is used to maintain contracts by
* using a controller object. This will invoke the controller with
* the contract when a lease operation is performed. A lease is
* renewed by changing the contract duration and passing that to
* the controller which will reestablish the expiry time for it.
*
* @author Niall Gallagher
*/
class ContractLease<T> implements Lease<T> {
/**
* This is the controller object used to handle contracts.
*/
private final ContractController<T> handler;
/**
* This is the contract object representing the lease.
*/
private final Contract<T> contract;
/**
* Constructor for the <code>ContractLease</code> object. This is
* used to create a lease which will maintain a contract using a
* controller object. Lease renewals are performed by changing the
* expiry duration on the contract and notifying the controller.
*
* @param handler this is used to manage the contract expiration
* @param contract this is the contract representing the lease
*/
public ContractLease(ContractController<T> handler, Contract<T> contract) {
this.handler = handler;
this.contract = contract;
}
/**
* 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 LeaseException if the lease expiry has passed
*/
public long getExpiry(TimeUnit unit) throws LeaseException {
return contract.getDelay(unit);
}
/**
* 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 dependant 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 LeaseException if the expiry has been passed
*/
public void renew(long duration, TimeUnit unit) throws LeaseException {
if(duration >= 0) {
contract.setDelay(duration, unit);
}
handler.renew(contract);
}
/**
* 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 LeaseException if the expiry has been passed
*/
public void cancel() throws LeaseException {
handler.cancel(contract);
}
/**
* 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
*/
public T getKey() {
return contract.getKey();
}
}