fix(config): make ClientIpWhiteList.isOpen volatile and null-safe

[daguimu]

Problem

ClientIpWhiteList.isOpen has two issues:

1. Visibility bug: The field is written by the config-load thread (in load()) and read by HTTP request threads (in isEnableWhitelist()). Without volatile, the Java Memory Model does not guarantee cross-thread visibility, so request threads may read a stale value indefinitely.

2. NullPointerException risk: isOpen is a Boolean wrapper, and acl.getIsOpen() can return null when the JSON field is absent. The isEnableWhitelist() method returns primitive boolean, so a null isOpen would cause auto-unboxing NPE.

Root Cause

• private static Boolean isOpen = false; — not volatile, not thread-safe for cross-thread reads/writes.
• isOpen = acl.getIsOpen(); — no null guard, yet downstream returns primitive boolean.

Fix

• Change Boolean isOpen to volatile boolean isOpen for guaranteed visibility.
• Use Boolean.TRUE.equals(acl.getIsOpen()) for null-safe assignment — treats null as false.

Tests Added

Change Point	Test
isOpen field is volatile	testIsOpenFieldIsVolatile() — reflection check on field modifiers
Valid JSON enables whitelist	testLoadValidContentEnablesWhitelist() — verifies isOpen=true and IP matching
Blank content disables whitelist	testLoadBlankContentDisablesWhitelist() — load then clear
Null isOpen does not throw NPE	testLoadNullIsOpenDoesNotThrowNpe() — JSON without isOpen field
isOpen=false works correctly	testLoadWithIsOpenFalse() — explicit false
Blank/null client IP validation	testIsLegalClientThrowsOnBlankInput() — boundary check
Invalid JSON does not crash	testLoadInvalidJsonDoesNotCrash() — malformed input

Impact

Only affects ClientIpWhiteList internal state. No API or behavioral change for correctly-formed inputs — the fix prevents stale reads and NPE on malformed ACL config.

[github-actions]

Thanks for your this PR. 🙏
Please check again for your PR changes whether contains any usage/api/configuration change such as Add new API , Add new configuration, Change default value of configuration.
If so, please add or update documents(markdown type) in docs/next/ for repository nacos-group/nacos-group.github.io

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感谢您提交的PR。 🙏
请再次查看您的PR内容，确认是否包含任何使用方式/API/配置参数的变更，如：新增API、新增配置参数、修改默认配置等操作。
如果是，请确保在提交之前，在仓库nacos-group/nacos-group.github.io中的docs/next/目录下添加或更新文档（markdown格式）。

[KomachiSion]

@daguimu Hi,

we are welcome you contribute nacos community and do many PR help nacos to do enhancement and bugfix.

But I suggest you submit issue to describe issues before submit PRs.

[KomachiSion]

And welcome provide an dingtalk number, which we can invite you join the nacos community contributor groups.

[daguimu]

And welcome provide an dingtalk number, which we can invite you join the nacos community contributor groups.
my dingtalk number is bazs8u9