Fix UnsupportedOperationException in DubboDefaultPropertiesEnvironmentPostProcessor.addOrReplace on immutable property source (#16268)

[wsyjh8]

What is the purpose of the change?

GitHub_issue: Fixes #16268

This pull request fixes the UnsupportedOperationException thrown by DubboDefaultPropertiesEnvironmentPostProcessor#addOrReplace when a defaultProperties source is already present and backed by an immutable map.

addOrReplace merged Dubbo's defaults by mutating the existing source's backing map in place via target.getSource().put(...). But MapPropertySource.getSource() returns the map the source was constructed with, which Spring does not guarantee is mutable. Since this post-processor runs at LOWEST_PRECEDENCE, another EnvironmentPostProcessor (e.g. Nacos / Spring Cloud bootstrap) may already have registered defaultProperties backed by an immutable map such as Guava ImmutableMap, so the put throws:

java.lang.UnsupportedOperationException
    at com.google.common.collect.ImmutableMap.put(ImmutableMap.java:814)
    at org.apache.dubbo.spring.boot.env.DubboDefaultPropertiesEnvironmentPostProcessor.addOrReplace(DubboDefaultPropertiesEnvironmentPostProcessor.java:134)

The fix copies the existing entries into a new mutable HashMap, merges Dubbo's defaults only for keys not already present (unchanged precedence), and replaces the source in place via MutablePropertySources.replace(...) — the same approach as Spring Boot's own DefaultPropertiesPropertySource#addOrMerge. The mutable case behaves identically; the immutable case no longer throws. No public signature or behaviour change, and the Java 8 language level is preserved.

Two regression tests were added in DubboDefaultPropertiesEnvironmentPostProcessorTest: one asserts an immutable-backed defaultProperties no longer throws, the other asserts an already-present key is still not overridden by Dubbo's default.

Verification

• git diff --check
• ./mvnw -pl dubbo-spring-boot-project/dubbo-spring-boot -am -Dtest=DubboDefaultPropertiesEnvironmentPostProcessorTest -Dsurefire.failIfNoSpecifiedTests=false test

Checklist

• Make sure there is a GitHub_issue field for the change.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit-test to verify your logic correction. If the new feature or significant change is committed, please remember to add sample in dubbo samples project.
• Make sure GitHub actions can pass.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.79%. Comparing base (990c513) to head (3e65d53).

Additional details and impacted files

@@             Coverage Diff              @@
##                3.3   #16313      +/-   ##
============================================
+ Coverage     60.77%   60.79%   +0.01%     
- Complexity    11763    11767       +4     
============================================
  Files          1953     1953              
  Lines         89203    89205       +2     
  Branches      13458    13458              
============================================
+ Hits          54216    54234      +18     
+ Misses        29414    29398      -16     
  Partials       5573     5573              

Flag	Coverage Δ
integration-tests-java21	32.17% <0.00%> (+0.04%)	⬆️
integration-tests-java8	32.28% <0.00%> (+0.03%)	⬆️
samples-tests-java21	32.19% <0.00%> (+0.01%)	⬆️
samples-tests-java8	29.86% <0.00%> (+0.02%)	⬆️
unit-tests-java11	59.02% <100.00%> (+<0.01%)	⬆️
unit-tests-java17	58.53% <100.00%> (+0.03%)	⬆️
unit-tests-java21	58.50% <100.00%> (+<0.01%)	⬆️
unit-tests-java25	58.46% <100.00%> (-0.05%)	⬇️
unit-tests-java8	59.05% <100.00%> (-0.01%)	⬇️

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[oneby-wang]

Hi, @wsyjh8, I'm also working on this issue. I noticed you've already submitted a PR, so I'm sharing my PR here as well for reference: oneby-wang#1.

[zrlw]

LGTM

[EarthChen]

LGTM