com.sun.jini.lease.landlord
Class LeaseDurationPolicy

java.lang.Object
  |
  +--com.sun.jini.lease.landlord.LeaseDurationPolicy

public class LeaseDurationPolicy

extends java.lang.Object

implements LeasePolicy

Provides an implementation of LeasePolicy that grants and renews leases based on constant values for maximum and default lease durations. When an instance of the class is created a LeaseManager may be associated with it. The manager will be notified when a Lease is created or renewed.

See Also:

Landlord, LeasedResource, LeaseManager, Lease

Constructor Summary

LeaseDurationPolicy(long maximum, long defaultLength, Landlord landlord, LeaseManager mgr, LandlordLeaseFactory factory)
Create a LeaseDurationPolicy that will handout the leases with the specified maximum and default durations.

Method Summary

protected long	calculateDuration(LeasedResource resource, long requestedDuration) Returns the duration this policy is willing to grant for the passed resource at this time.
protected long	currentTime() Method that provides some notion of the current time in milliseconds since the beginning of the epoch.
boolean	ensureCurrent(LeasedResource resource) Returns true if the lease on the passed resource has not expired yet.
Lease	leaseFor(LeasedResource resource, long requestedDuration) Factory method that returns lease objects for the specified resource.
long	renew(LeasedResource resource, long requestedDuration) Renews the expiration of the passed resource.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

LeaseDurationPolicy

public LeaseDurationPolicy(long maximum,
                           long defaultLength,
                           Landlord landlord,
                           LeaseManager mgr,
                           LandlordLeaseFactory factory)

Create a LeaseDurationPolicy that will handout the leases with the specified maximum and default durations. Leases with a requested duration less than maximum will be granted exactly.

Parameters:

maximum - The length in milliseconds of the longest lease this manager should handout.

defaultLength - The length in milliseconds of lease this manager should handout if the client expresses no preference.

landlord - The owner of the leased resources being managed by this manager.

mgr - LeaseManager that will be notified of lease creations and renewals. May be null

factory - Factory that will be used to generate new leases. If null a LandlordLease factory will be used.

Throws:

java.lang.IllegalArgumentException - thrown if defaultLength and maximum are not larger than 0 or if landlord is null.

Method Detail

leaseFor

public Lease leaseFor(LeasedResource resource,
                      long requestedDuration)
               throws LeaseDeniedException

Factory method that returns lease objects for the specified resource. The lease will call the Landlord object passed to the manager's constructor to handle renewal and cancel requests. The cookie passed to these calls will be the same as the cookie returned by resource.getCookie(). The duration of the lease will be affected by the requested duration, and the default and maximum parameters passed to the constructor.

Specified by:

leaseFor in interface LeasePolicy

Parameters:

resource - The resource the lease is for. resource.setExpiration will be called to initialize the expiration time of the resource.

requestedDuration - The length of lease the client wants.

Returns:

A lease for the passed resource

Throws:

java.lang.IllegalArgumentException - thrown if requestedDuration is less than 0 and not equal to Lease.ANYLENGTH or Lease.FOREVER.

renew

public long renew(LeasedResource resource,
                  long requestedDuration)

Renews the expiration of the passed resource. The duration of renewal is based on the requested duration and the default and maximum parameters passed to the constructor.

Specified by:

renew in interface LeasePolicy

Parameters:

resource - The resource having its lease renewed. resource.setExpiration will be called to update the expiration time of the resource.

requestedDuration - The new duration the client wants

Returns:

The new duration the lease should have.

Throws:

java.lang.IllegalArgumentException - thrown if requestedDuration is less than 0 and not equal to Lease.ANYLENGTH or Lease.FOREVER.

ensureCurrent

public boolean ensureCurrent(LeasedResource resource)

Returns true if the lease on the passed resource has not expired yet.

Specified by:

ensureCurrent in interface LeasePolicy

calculateDuration

protected long calculateDuration(LeasedResource resource,
                                 long requestedDuration)

Returns the duration this policy is willing to grant for the passed resource at this time. The duration actually granted will be shorter if the duration extends pass the end of the epoch. Must return a positive number.

Parameters:

resource - The resource having a lease granted or renewed

requestedDuration - The duration the client wants

Throws:

java.lang.IllegalArgumentException - thrown if requestedDuration is less than 0 and not equal to Lease.ANYLENGTH or Lease.FOREVER.

currentTime

protected long currentTime()

Method that provides some notion of the current time in milliseconds since the beginning of the epoch. Default implementation calls System.currentTimeMillis()