Third party lib for object pool with expiration time in Java

问题

I'm on a webservice server and I have objects with an internal connection.
Initializing this connection takes really long so my idea was to use an object pool to reuse the connections among different requests.

The objects are connected to each user, so i prefer to use the username as key and the connection as value. But I don't want to have the connection open forever. Maybe after a while it should be destroyed if the user does not start requests any more.

I thought about using the apache object pool but i didn't see expiration there (correct me if i'm wrong)

The ehcache offers me notifications about eviction and expiration, but not triggered after the timeout was over, only if the cached object was touched again.

Does someone know a lib which can do this job for me?

回答1:

Take a look at http://commons.apache.org/proper/commons-pool/api-1.6/org/apache/commons/pool/impl/GenericObjectPool.html

From the javadoc:

Optionally, one may configure the pool to examine and possibly evict objects
as they sit idle in the pool and to ensure that a minimum number of idle
objects are available. This is performed by an "idle object eviction" thread,
which runs asynchronously. Caution should be used when configuring this
optional feature. Eviction runs contend with client threads for access to
objects in the pool, so if they run too frequently performance issues may
result.

.... 

minEvictableIdleTimeMillis specifies the minimum amount of time that 
an object may sit idle in the pool before it is eligible for eviction
due to idle time. When non-positive, no object will be dropped from 
the pool due to idle time alone. This setting has no effect unless
timeBetweenEvictionRunsMillis > 0. The default setting for this 
parameter is 30 minutes.

Implement a PoolableObjectFactory that creates your connections and also implement the PoolableObjectFactory.destroyObject(T object) method to close your connection. This method will be invoked by the GenericObejctPool when an objects gets evicted.

回答2:

Inspired by assylia's idea i used the guava way here my solution

final RemovalListener<Integer, Connection> removalListener = new RemovalListener<Integer, Connection>() {
    @Override
    public void onRemoval(final RemovalNotification<Integer, Connection> notification) {
        disconnect(notification.getValue());
    }
};

Cache<Integer, Connection> cache = CacheBuilder.newBuilder().maximumSize(20)
        .expireAfterAccess(30, TimeUnit.SECONDS)
        .removalListener(removalListener).build();
final ScheduledExecutorService cacheMaintanance = Executors.newSingleThreadScheduledExecutor();
cacheMaintanance.scheduleAtFixedRate(new Runnable() {
    @Override
    public void run() {
        cache.cleanUp();
    }
}, 10, 10, TimeUnit.SECONDS);

回答3:

New Generic interface was added to this recently:

http://commons.apache.org/proper/commons-pool/

来源：https://stackoverflow.com/questions/17678269/third-party-lib-for-object-pool-with-expiration-time-in-java

标签

java

object-pooling