feat: add Spring 6 REST adapter artifact

[SavitarC]

What changed

• add a Java 17 dubbo-rest-spring6 artifact by copying the legacy REST Spring adapter and applying only the Spring 6 / Jakarta Servlet compile-time adaptations
• preserve the legacy dubbo-rest-spring artifact and its Spring 5 / javax.servlet runtime behavior
• keep the existing REST Spring public FQCNs and SPI registrations in the parallel artifact
• register the new module in the root JDK 17 profile, release profile, BOM, and .artifacts
• remove dubbo-rest-spring from the dubbo and dubbo-all-shaded aggregate JARs so neither aggregate chooses an adapter
• keep per-artifact marker resources for a future classpath checker; this PR does not consume them at runtime
• add Spring 5/6 API parity, servlet namespace, Boot 2/3 dependency composition, basic @RequestMapping end-to-end, and Spring 6.1 compatibility coverage
• register dubbo-test-rest-spring6.1 under the JDK 17+ test profile

Why

dubbo-rest-spring is compiled against Spring 5 and javax.servlet. Spring Framework 6 changed the relevant MVC method descriptors to jakarta.servlet, so the legacy artifact cannot support that path without breaking Spring 5 compatibility.

A separate artifact keeps the Spring 5 contract unchanged while providing a Spring 6 / Jakarta-compatible implementation.

Fixes #16387.

Dependency selection

Applications using Triple REST with Spring MVC annotations must explicitly select exactly one adapter. Applications that do not use the REST Spring integration may include neither.

Spring Boot 2 / Spring Framework 5

<dependency>
  <groupId>org.apache.dubbo</groupId>
  <artifactId>dubbo-spring-boot-starter</artifactId>
  <version>${dubbo.version}</version>
</dependency>
<dependency>
  <groupId>org.apache.dubbo</groupId>
  <artifactId>dubbo-rest-spring</artifactId>
  <version>${dubbo.version}</version>
</dependency>

Spring Boot 3 / Spring Framework 6

<dependency>
  <groupId>org.apache.dubbo</groupId>
  <artifactId>dubbo-spring-boot-starter</artifactId>
  <version>${dubbo.version}</version>
</dependency>
<dependency>
  <groupId>org.apache.dubbo</groupId>
  <artifactId>dubbo-spring-boot-3-autoconfigure</artifactId>
  <version>${dubbo.version}</version>
</dependency>
<dependency>
  <groupId>org.apache.dubbo</groupId>
  <artifactId>dubbo-rest-spring6</artifactId>
  <version>${dubbo.version}</version>
</dependency>

When the Dubbo BOM manages these artifacts, the individual <version> elements may be omitted.

Having both REST Spring adapters on one classpath is an unsupported configuration. This version does not provide runtime conflict detection; users must ensure the classpath contains at most one adapter.

Scope

This PR is limited to the Spring 6 artifact split, build/distribution metadata, marker resources, and the tests needed to validate that split. It intentionally does not include:

• FrameworkModel initialization rollback or cleanup changes
• REST adapter classpath fail-fast logic
• shared Triple REST filter lifecycle changes
• JAX-RS exception mapper changes
• legacy Spring adapter interceptor or exception-handler behavior changes
• shared mapping semantics, Spring MVC behavior alignment, parameter binding, or CORS fixes

Validation

• JDK 8: dubbo-rest-spring 58 tests, 11 skipped, 0 failures
• JDK 25: dubbo-rest-spring6 52 tests, 0 failures
• Spring 6.1 @RequestMapping compatibility: 1 test, 0 failures
• dependency/distribution FileTest: 8 tests, 0 failures
• Boot 2 and Boot 3 composition tests each find exactly one matching adapter and marker
• dubbo and dubbo-all-shaded binary/source JARs contain neither REST Spring adapter
• CI unit tests pass on JDK 8, 11, 17, 21, and 25; all integration-test jobs pass
• cross-repository Java 21 validation against fix: select Spring 6 REST adapter for samples dubbo-samples#1297 (23cd268bb1) with -Ddubbo.version=3.3.7-SNAPSHOT -Dspring.version=6.1.5 -Ddubbo.rest.spring6=true:
  • dubbo-samples-triple-rest-springmvc: provider registered 48 REST mappings; all 36 ConsumerIT tests passed
  • dubbo-samples-triple-rest-spring-security: provider registered the Spring MVC REST mappings; both ResourceServerIT tests passed
• with the sample profile disabled, the packaged sample contains neither REST Spring adapter and /demo/hello returns 404 Invoker not found, confirming the explicit-selection behavior
• git diff --check passed

Current CI coordination

The samples jobs in this PR currently check out apache/dubbo-samples@master and do not enable -Ddubbo.rest.spring6=true. Because apache/dubbo-samples#1297 is still open and its profile is opt-in, the Java 21 samples job tests the aggregate without a REST Spring adapter and fails with 404 Invoker not found.

The cancelled samples-result job and skipped Jacoco jobs are downstream consequences of that samples failure. The adapter tests, unit tests, and integration-test jobs are green. The cross-repository check cannot become green until the samples ref/profile is available to the workflow or equivalent merge coordination is accepted.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 33.64486% with 355 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.73%. Comparing base (eb1d8ab) to head (ea51d47).

Files with missing lines	Patch %	Lines
.../rest/support/spring/SpringResponseRestFilter.java	8.60%	81 Missing and 4 partials ⚠️
...support/spring/MatrixVariableArgumentResolver.java	4.00%	48 Missing ⚠️
...upport/spring/SpringMvcRequestMappingResolver.java	53.24%	26 Missing and 10 partials ⚠️
...rest/support/spring/HandlerInterceptorAdapter.java	3.03%	32 Missing ⚠️
...col/tri/rest/support/spring/SpringRestToolKit.java	54.54%	19 Missing and 6 partials ⚠️
...st/support/spring/CookieValueArgumentResolver.java	9.09%	20 Missing ⚠️
...st/support/spring/RequestBodyArgumentResolver.java	25.00%	14 Missing and 1 partial ⚠️
...t/support/spring/PathVariableArgumentResolver.java	12.50%	14 Missing ⚠️
...ol/tri/rest/support/spring/BeanArgumentBinder.java	63.63%	8 Missing and 4 partials ⚠️
...st/support/spring/RequestPartArgumentResolver.java	14.28%	12 Missing ⚠️
... and 10 more

Additional details and impacted files

@@             Coverage Diff              @@
##                3.3   #16394      +/-   ##
============================================
- Coverage     60.90%   58.73%   -2.18%     
+ Complexity    11763      157   -11606     
============================================
  Files          1953     1976      +23     
  Lines         89266    89801     +535     
  Branches      13471    13559      +88     
============================================
- Hits          54367    52741    -1626     
- Misses        29319    31321    +2002     
- Partials       5580     5739     +159     

Flag	Coverage Δ
integration-tests-java21	?
integration-tests-java8	?
samples-tests-java21	?
samples-tests-java8	?
unit-tests-java11	59.10% <ø> (-0.01%)	⬇️
unit-tests-java17	58.43% <33.64%> (-0.13%)	⬇️
unit-tests-java21	58.45% <33.64%> (-0.14%)	⬇️
unit-tests-java25	58.42% <33.64%> (-0.13%)	⬇️
unit-tests-java8	59.16% <ø> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.