public abstract class ReferenceManager<G> extends Object implements Closeable
ReferenceManager
implementations for their maybeRefresh()
semantics.Modifier and Type | Class and Description |
---|---|
static interface |
ReferenceManager.RefreshListener
Use to receive notification when a refresh has
finished.
|
Constructor and Description |
---|
ReferenceManager() |
Modifier and Type | Method and Description |
---|---|
G |
acquire()
Obtain the current reference.
|
void |
addListener(ReferenceManager.RefreshListener listener)
Adds a listener, to be notified when a reference is refreshed/swapped.
|
void |
close()
Closes this ReferenceManager to prevent future
acquiring . |
boolean |
maybeRefresh()
You must call this (or
maybeRefreshBlocking() ), periodically, if
you want that acquire() will return refreshed instances. |
void |
maybeRefreshBlocking()
You must call this (or
maybeRefresh() ), periodically, if you want
that acquire() will return refreshed instances. |
void |
release(G reference)
Release the reference previously obtained via
acquire() . |
void |
removeListener(ReferenceManager.RefreshListener listener)
Remove a listener added with
addListener(RefreshListener) . |
public final G acquire() throws IOException
release(G)
; it's best to do so in a finally clause, and set
the reference to null
to prevent accidental usage after it has been
released.AlreadyClosedException
- if the reference manager has been closed
.IOException
public final void close() throws IOException
Closes this ReferenceManager to prevent future acquiring
. A
reference manager should be closed if the reference to the managed resource
should be disposed or the application using the ReferenceManager
is shutting down. The managed resource might not be released immediately,
if the ReferenceManager
user is holding on to a previously
acquired
reference. The resource will be released once
when the last reference is released
. Those
references can still be used as if the manager was still active.
Applications should not acquire
new references from this
manager once this method has been called. Acquiring
a
resource on a closed ReferenceManager
will throw an
AlreadyClosedException
.
close
in interface Closeable
close
in interface AutoCloseable
IOException
- if the underlying reader of the current reference could not be closedpublic final boolean maybeRefresh() throws IOException
maybeRefreshBlocking()
), periodically, if
you want that acquire()
will return refreshed instances.
Threads: it's fine for more than one thread to call this at once. Only the first thread will attempt the refresh; subsequent threads will see that another thread is already handling refresh and will return immediately. Note that this means if another thread is already refreshing then subsequent threads will return right away without waiting for the refresh to complete.
If this method returns true it means the calling thread either refreshed or that there were no changes to refresh. If it returns false it means another thread is currently refreshing.
IOException
- if refreshing the resource causes an IOException
AlreadyClosedException
- if the reference manager has been closed
.public final void maybeRefreshBlocking() throws IOException
maybeRefresh()
), periodically, if you want
that acquire()
will return refreshed instances.
Threads: unlike maybeRefresh()
, if another thread is
currently refreshing, this method blocks until that thread completes. It is
useful if you want to guarantee that the next call to acquire()
will return a refreshed instance. Otherwise, consider using the
non-blocking maybeRefresh()
.
IOException
- if refreshing the resource causes an IOException
AlreadyClosedException
- if the reference manager has been closed
.public final void release(G reference) throws IOException
acquire()
.
NOTE: it's safe to call this after close()
.
IOException
- if the release operation on the given resource throws an IOException
public void addListener(ReferenceManager.RefreshListener listener)
public void removeListener(ReferenceManager.RefreshListener listener)
addListener(RefreshListener)
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