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diff --git a/simple/simple-common/src/main/java/org/simpleframework/common/lease/Lease.java b/simple/simple-common/src/main/java/org/simpleframework/common/lease/Lease.java
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+/*
+ * 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();  
+
+}