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8254566: Clarify the spec of ClassLoader::getClassLoadingLock for non-parallel capable loader

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Reviewed-by: dholmes, darcy
This commit is contained in:
Mandy Chung 2023-07-03 16:04:35 +00:00
parent f393975d1b
commit b9198f9931
1 changed files with 16 additions and 7 deletions

23
src/java.base/share/classes/java/lang/ClassLoader.java

@ -1,5 +1,5 @@
/*
* Copyright (c) 2013, 2022, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2013, 2023, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2019, Azul Systems, Inc. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
@ -647,11 +647,20 @@ public abstract class ClassLoader {
/**
* Returns the lock object for class loading operations.
* For backward compatibility, the default implementation of this method
* behaves as follows. If this ClassLoader object is registered as
* parallel capable, the method returns a dedicated object associated
* with the specified class name. Otherwise, the method returns this
* ClassLoader object.
*
* @implSpec
* If this {@code ClassLoader} object is registered as parallel capable,
* this method returns a dedicated object associated with the specified
* class name. Otherwise, this method returns this {@code ClassLoader} object.
*
* @apiNote
* This method allows parallel capable class loaders to implement
* finer-grained locking schemes such that multiple threads may load classes
* concurrently without deadlocks. For non-parallel-capable class loaders,
* the {@code ClassLoader} object is synchronized on during the class loading
* operations. Class loaders with non-hierarchical delegation should be
* {@linkplain #registerAsParallelCapable() registered as parallel capable}
* to prevent deadlocks.
*
* @param className
* The name of the to-be-loaded class
@ -659,7 +668,7 @@ public abstract class ClassLoader {
* @return the lock for class loading operations
*
* @throws NullPointerException
* If registered as parallel capable and {@code className} is null
* If registered as parallel capable and {@code className} is {@code null}
*
* @see #loadClass(String, boolean)
*