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package com.sun.xml.ws.util;
import com.sun.xml.ws.api.pipe.Tube;
import com.sun.xml.ws.api.pipe.TubeCloner;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.lang.ref.WeakReference;
/**
* General-purpose object pool.
*
*
* In many parts of the runtime, we need to pool instances of objects that
* are expensive to create (such as JAXB objects, StAX parsers, {@link Tube} instances.)
*
*
* This class provides a default implementation of such a pool.
*
* TODO: improve the implementation
*
* @author Kohsuke Kawaguchi
*/
public abstract class Pool {
// volatile since multiple threads may access queue reference
private volatile WeakReference> queue;
/**
* Gets a new object from the pool.
*
*
* If no object is available in the pool, this method creates a new one.
*
* @return
* always non-null.
*/
public final T take() {
T t = getQueue().poll();
if(t==null)
return create();
return t;
}
private ConcurrentLinkedQueue getQueue() {
WeakReference> q = queue;
if (q != null) {
ConcurrentLinkedQueue d = q.get();
if (d != null)
return d;
}
// overwrite the queue
ConcurrentLinkedQueue d = new ConcurrentLinkedQueue();
queue = new WeakReference>(d);
return d;
}
/**
* Returns an object back to the pool.
*/
public final void recycle(T t) {
getQueue().offer(t);
}
/**
* Creates a new instance of object.
*
*
* This method is used when someone wants to
* {@link #take() take} an object from an empty pool.
*
*
* Also note that multiple threads may call this method
* concurrently.
*/
protected abstract T create();
/**
* JAXB {@link javax.xml.bind.Marshaller} pool.
*/
public static final class Marshaller extends Pool {
private final JAXBContext context;
public Marshaller(JAXBContext context) {
this.context = context;
}
@Override
protected javax.xml.bind.Marshaller create() {
try {
return context.createMarshaller();
} catch (JAXBException e) {
// impossible
throw new AssertionError(e);
}
}
}
/**
* JAXB {@link javax.xml.bind.Marshaller} pool.
*/
public static final class Unmarshaller extends Pool {
private final JAXBContext context;
public Unmarshaller(JAXBContext context) {
this.context = context;
}
@Override
protected javax.xml.bind.Unmarshaller create() {
try {
return context.createUnmarshaller();
} catch (JAXBException e) {
// impossible
throw new AssertionError(e);
}
}
}
/**
* {@link Tube} pool.
*/
public static final class TubePool extends Pool {
private final Tube master;
public TubePool(Tube master) {
this.master = master;
recycle(master); // we'll use master as a part of the pool, too.
}
@Override
protected Tube create() {
return TubeCloner.clone(master);
}
/**
*
* @return master tubeline from pool
* @deprecated Expected to be used in rare cases where access to master
* tubeline is required and safe, such as Stub.close()."
*/
@Deprecated()
public final Tube takeMaster() {
return master;
}
}
}