WW-3353 fix(junit): make StrutsRestTestCase work against a REST/Convention app

[lukaszlenart]

Fixes WW-3353

StrutsRestTestCase (added by WW-4549 as the answer to this ticket) has never had a test and could not actually run a REST action to completion. Two defects, each watched failing before the fix:

1. initServletMockObjects() order — the MockServletContext was built before ConventionPluginResourceLoader was assigned, so the loader was a dead assignment and Convention could not resolve results under /WEB-INF/content: No result defined for action org.demo.rest.example.OrdersController and result show. Creating the loader first fixes it.
2. Missing spring-web — spring-test's MockHttpServletResponse needs org.springframework.http.MediaType, and the plugin only reached spring-web through its optional struts2-spring-plugin dependency. A project following the docs (Spring plugin only for Spring-managed actions) got NoClassDefFoundError on the first test. Declared directly; the version is BOM-managed and already resolved transitively elsewhere.

Adds OrdersControllerRestTestCaseTest in apps/rest-showcase — the first coverage of StrutsRestTestCase — executing GET /orders/3 through the proxy (id bound from the path, Convention result resolved) and rendering /orders/3.json. The showcase POM gets the junit plugin at test scope and the servlet/JSP APIs at provided scope, as apps/showcase already declares.

On the ticket's original symptom ("/orders/3 doesn't call setId"): the attached test called action.show() directly without proxy.execute(), so no interceptor ran; with execute() the id binds even on the plain test case. The title claim was still true, for the two reasons above.

Verified: mvn test -pl apps/rest-showcase -Dtest=OrdersControllerRestTestCaseTest (2/2) and the junit plugin's own suite (12/12).

🤖 Generated with Claude Code

[sonarqubecloud]

Quality Gate failed

Failed conditions
0.0% Coverage on New Code (required ≥ 80%)

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