[#16098] Fix resource leaks and improve code quality in ConfigUtils

[DocJlm]

What is the purpose of the change?

Fix resource leaks and improve code quality in ConfigUtils (dubbo-common module). Fixes #16098.

• Refactor loadProperties() to use try-with-resources for FileInputStream, eliminating manual close() calls and potential resource leaks
• Refactor multi-file loading loop to use try-with-resources for InputStream from URL, removing empty catch blocks
• Fix resource leak in loadMigrationRule() where InputStream from URL was never closed after reading

The most critical fix is in loadMigrationRule() where an InputStream opened via url.openStream() is never closed, which can lead to file handle leaks in long-running applications.

Checklist

• Make sure there is a GitHub issue filed for the change.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• This PR only changes resource management patterns without altering logic. Existing tests cover the functionality, no new unit tests needed.
• GitHub Actions should pass — no logic changes, only resource management improvements.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 60.80%. Comparing base (06334a5) to head (b96c4f0).

Files with missing lines	Patch %	Lines
...ava/org/apache/dubbo/common/utils/ConfigUtils.java	88.88%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                3.3   #16097      +/-   ##
============================================
- Coverage     60.80%   60.80%   -0.01%     
- Complexity    11750    11753       +3     
============================================
  Files          1953     1953              
  Lines         89121    89118       -3     
  Branches      13443    13444       +1     
============================================
- Hits          54192    54189       -3     
+ Misses        29369    29367       -2     
- Partials       5560     5562       +2     

Flag	Coverage Δ
integration-tests-java21	32.12% <0.00%> (-0.06%)	⬇️
integration-tests-java8	32.24% <0.00%> (-0.02%)	⬇️
samples-tests-java21	32.14% <0.00%> (-0.04%)	⬇️
samples-tests-java8	29.74% <0.00%> (-0.01%)	⬇️
unit-tests-java11	59.06% <88.88%> (-0.01%)	⬇️
unit-tests-java17	58.54% <88.88%> (-0.03%)	⬇️
unit-tests-java21	58.57% <88.88%> (+0.01%)	⬆️
unit-tests-java25	58.50% <88.88%> (-0.01%)	⬇️
unit-tests-java8	59.06% <88.88%> (-0.02%)	⬇️

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[LI123456mo]

Hi @DocJlm , I think the code is already implementing the "StringBuffer"?

[DocJlm]

Hi @DocJlm , I think the code is already implementing the "StringBuffer"?

Hi @LI123456mo, yes, you're right. I initially changed StringBuffer to StringBuilder in replaceProperty(), but the CI build failed because Matcher.appendReplacement() and Matcher.appendTail() only accept StringBuffer in Java 8 (the StringBuilder overload was added in Java 9).Since Dubbo needs to maintain Java 8 compatibility, I reverted that change. The remaining changes in this PR focus on fixing resource leaks using try-with-resources.

[LI123456mo]

Hi @DocJlm , I think the code is already implementing the "StringBuffer"?

Hi @LI123456mo, yes, you're right. I initially changed StringBuffer to StringBuilder in replaceProperty(), but the CI build failed because Matcher.appendReplacement() and Matcher.appendTail() only accept StringBuffer in Java 8 (the StringBuilder overload was added in Java 9).Since Dubbo needs to maintain Java 8 compatibility, I reverted that change. The remaining changes in this PR focus on fixing resource leaks using try-with-resources.

If it is java 8 you are right to implement "StringBuffer"