RFR: 8364544: Extract the checks of AtomicXxxFieldUpdater into a common place [v2]

[Chen Liang]

On Tue, 25 Nov 2025 02:52:33 GMT, Steve Armstrong <duke at openjdk.org> wrote:

>> The three AtomicXxxFieldUpdater classes (AtomicIntegerFieldUpdater, AtomicLongFieldUpdater, and AtomicReferenceFieldUpdater) contain duplicate field validation and access checking logic in their constructors and helper methods.
>> 
>> This change extracts the common validation and utility methods into a new package-private class FieldUpdaterUtil to eliminate code duplication and improve maintainability.
>> 
>> Changes:
>> - Added new FieldUpdaterUtil class with static utility methods:
>>   * validateField() - validates field type, volatile, and static checks
>>   * computeAccessClass() - determines correct class for access checks
>>   * isSamePackage() - checks if two classes are in same package
>>   * isAncestor() - checks classloader delegation chain
>> 
>> - Updated AtomicIntegerFieldUpdater to use FieldUpdaterUtil
>>   * Simplified constructor to use validateField() and computeAccessClass()
>>   * Removed duplicate isAncestor() and isSamePackage() methods
>> 
>> - Updated AtomicLongFieldUpdater to use FieldUpdaterUtil
>>   * Simplified constructor to use validateField() and computeAccessClass()
>>   * Removed duplicate isAncestor() and isSamePackage() methods
>> 
>> - Updated AtomicReferenceFieldUpdater to use FieldUpdaterUtil
>>   * Simplified constructor to use validateField() and computeAccessClass()
>>   * Removed duplicate isAncestor() and isSamePackage() methods
>> 
>> Existing tests in test/jdk/java/util/concurrent/tck and test/jdk/java/util/concurrent/atomic verify that the refactoring preserves the original behavior.
>
> Steve Armstrong has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Replace legacy ReflectUtil with modern Reflection API
>   
>   Replaced sun.reflect.misc.ReflectUtil with jdk.internal.reflect.Reflection
>   in atomic field updaters. Added getFieldWithAccess() method and
>   FieldAndModifiers record to FieldUpdaterUtil to consolidate field
>   access checking logic.

Changes requested by liach (Reviewer).

src/java.base/share/classes/java/util/concurrent/atomic/AtomicIntegerFieldUpdater.java line 391:

> 389:             FieldUpdaterUtil.FieldAndModifiers fam =
> 390:                 FieldUpdaterUtil.getFieldWithAccess(tclass, fieldName, caller);
> 391:             FieldUpdaterUtil.validateField(fam.field, int.class);

Consider using this code sequence:


Field field = FieldUpdaterUtil.findValidatedField(tclass, fieldName, caller, int.class);
this.cclass = FieldUpdaterUtil.computeAccessClass(tclass, caller, field.getModifiers());
this.tclass = tclass;
this.offset = U.objectFieldOffset(field);

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PR Review: https://git.openjdk.org/jdk/pull/28464#pullrequestreview-3503100202
PR Review Comment: https://git.openjdk.org/jdk/pull/28464#discussion_r2558406263