public static final class ExtensionFinder.Sezpoz extends ExtensionFinder
Extension
marker.
Uses Sezpoz as the underlying mechanism.
ExtensionFinder.DefaultGuiceExtensionAnnotation, ExtensionFinder.GuiceExtensionAnnotation<T extends Annotation>, ExtensionFinder.GuiceFinder, ExtensionFinder.Sezpoz
ExtensionPoint.LegacyInstancesAreScopedToHudson
Constructor and Description |
---|
Sezpoz() |
Modifier and Type | Method and Description |
---|---|
<T> Collection<ExtensionComponent<T>> |
find(Class<T> type,
Hudson jenkins)
Discover extensions of the given type.
|
ExtensionComponentSet |
refresh()
Rebuilds the internal index, if any, so that future
ExtensionFinder.find(Class, Hudson) calls
will discover components newly added to PluginManager.uberClassLoader . |
void |
scout(Class extensionType,
Hudson hudson)
Performs class initializations without creating instances.
|
_find, findExtensions, isRefreshable
public ExtensionComponentSet refresh()
ExtensionFinder.find(Class, Hudson)
calls
will discover components newly added to PluginManager.uberClassLoader
.
The point of the refresh operation is not to disrupt instances of already loaded ExtensionComponent
s,
and only instantiate those that are new. Otherwise this will break the singleton semantics of various
objects, such as Descriptor
s.
The behaviour is undefined if ExtensionFinder.isRefreshable()
is returning false.
SezPoz implements value-equality of IndexItem
, so
refresh
in class ExtensionFinder
ExtensionFinder.isRefreshable()
public <T> Collection<ExtensionComponent<T>> find(Class<T> type, Hudson jenkins)
ExtensionFinder
This method is called only once per the given type after all the plugins are loaded, so implementations need not worry about caching.
This method should return all the known components at the time of the call, including
those that are discovered later via ExtensionFinder.refresh()
, even though those components
are separately returned in ExtensionComponentSet
.
find
in class ExtensionFinder
T
- The type of the extension points. This is not bound to ExtensionPoint
because
of Descriptor
, which by itself doesn't implement ExtensionPoint
for
a historical reason.jenkins
- Jenkins whose behalf this extension finder is performing lookup.public void scout(Class extensionType, Hudson hudson)
ExtensionFinder
ExtensionFinder
s.
That is, one thread can try to list extensions, which results in ExtensionFinder
loading and initializing classes. This happens inside a context of a lock, so that
another thread that tries to list the same extensions don't end up creating different
extension instances. So this activity locks extension list first, then class initialization next.
In the mean time, another thread can load and initialize a class, and that initialization can eventually results in listing up extensions, for example through static initializer. Such activity locks class initialization first, then locks extension list.
This inconsistent locking order results in a dead lock, you see.
So to reduce the likelihood, this method is called in prior to ExtensionFinder.find(Class,Hudson)
invocation,
but from outside the lock. The implementation is expected to perform all the class initialization activities
from here.
See https://bugs.openjdk.java.net/browse/JDK-4993813 for how to force a class initialization. Also see http://kohsuke.org/2010/09/01/deadlock-that-you-cant-avoid/ for how class initialization can results in a dead lock.
scout
in class ExtensionFinder
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