/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 com.frameworkset.commons.pool2;
import java.io.PrintWriter;
import java.util.Deque;
/**
* Defines the wrapper that is used to track the additional information, such as
* state, for the pooled objects.
* <p>
* Implementations of this class are required to be thread-safe.
*
* @param <T> the type of object in the pool
*
* @version $Revision: $
*
* @since 2.0
*/
public interface PooledObject<T> extends Comparable<PooledObject<T>> {
/**
* Obtain the underlying object that is wrapped by this instance of
* {@link PooledObject}.
*
* @return The wrapped object
*/
T getObject();
/**
* Obtain the time (using the same basis as
* {@link System#currentTimeMillis()}) that this object was created.
*
* @return The creation time for the wrapped object
*/
long getCreateTime();
/**
* Obtain the time in milliseconds that this object last spent in the the
* active state (it may still be active in which case subsequent calls will
* return an increased value).
*
* @return The time in milliseconds last spent in the active state
*/
long getActiveTimeMillis();
/**
* Obtain the time in milliseconds that this object last spend in the the
* idle state (it may still be idle in which case subsequent calls will
* return an increased value).
*
* @return The time in milliseconds last spent in the idle state
*/
long getIdleTimeMillis();
/**
* Obtain the time the wrapped object was last borrowed.
*
* @return The time the object was last borrowed
*/
long getLastBorrowTime();
/**
* Obtain the time the wrapped object was last returned.
*
* @return The time the object was last returned
*/
long getLastReturnTime();
/**
* Return an estimate of the last time this object was used. If the class
* of the pooled object implements {@link TrackedUse}, what is returned is
* the maximum of {@link TrackedUse#getLastUsed()} and
* {@link #getLastBorrowTime()}; otherwise this method gives the same
* value as {@link #getLastBorrowTime()}.
*
* @return the last time this object was used
*/
long getLastUsedTime();
/**
* Orders instances based on idle time - i.e. the length of time since the
* instance was returned to the pool. Used by the GKOP idle object evictor.
*<p>
* Note: This class has a natural ordering that is inconsistent with
* equals if distinct objects have the same identity hash code.
* <p>
* {@inheritDoc}
*/
@Override
int compareTo(PooledObject<T> other);
@Override
boolean equals(Object obj);
@Override
int hashCode();
/**
* Provides a String form of the wrapper for debug purposes. The format is
* not fixed and may change at any time.
* <p>
* {@inheritDoc}
*/
@Override
String toString();
/**
* Attempt to place the pooled object in the
* {@link PooledObjectState#EVICTION} state.
*
* @return <code>true</code> if the object was placed in the
* {@link PooledObjectState#EVICTION} state otherwise
* <code>false</code>
*/
boolean startEvictionTest();
/**
* Called to inform the object that the eviction test has ended.
*
* @param idleQueue The queue of idle objects to which the object should be
* returned
*
* @return Currently not used
*/
boolean endEvictionTest(Deque<PooledObject<T>> idleQueue);
/**
* Allocates the object.
*
* @return {@code true} if the original state was {@link PooledObjectState#IDLE IDLE}
*/
boolean allocate();
/**
* Deallocates the object and sets it {@link PooledObjectState#IDLE IDLE}
* if it is currently {@link PooledObjectState#ALLOCATED ALLOCATED}.
*
* @return {@code true} if the state was {@link PooledObjectState#ALLOCATED ALLOCATED}
*/
boolean deallocate();
/**
* Sets the state to {@link PooledObjectState#INVALID INVALID}
*/
void invalidate();
/**
* Is abandoned object tracking being used? If this is true the
* implementation will need to record the stack trace of the last caller to
* borrow this object.
*
* @param logAbandoned The new configuration setting for abandoned
* object tracking
*/
void setLogAbandoned(boolean logAbandoned);
/**
* Record the current stack trace as the last time the object was used.
*/
void use();
/**
* Prints the stack trace of the code that borrowed this pooled object and
* the stack trace of the last code to use this object (if available) to
* the supplied writer.
*
* @param writer The destination for the debug output
*/
void printStackTrace(PrintWriter writer);
/**
* Returns the state of this object.
* @return state
*/
PooledObjectState getState();
/**
* Marks the pooled object as abandoned.
*/
void markAbandoned();
/**
* Marks the object as returning to the pool.
*/
void markReturning();
// TODO: Uncomment this for version 3 (can't add it to 2.x as it will break
// API compatibility)
///**
// * Get the number of times this object has been borrowed.
// */
//long getBorrowedCount();
}