chore: audit and tighten linting exceptions

[wphillipmoore]

Linting Exception Audit

Audit from wphillipmoore/mq-rest-admin-common#118.

Current Exceptions (~128 total)

Config-Level

• Checkstyle: package-info.java and module-info.java exempt from all checks
• PMD ruleset: 22 rules excluded (mostly Design complexity), 4 thresholds raised (CyclomaticComplexity→15, CognitiveComplexity→20, NPathComplexity→300, NestedIf→4)
• JaCoCo: excludes package-info.class, *IT.class, examples/*.class
• Error Prone: NullAway enabled for production, disabled for test code

Source Code Inline (23)

• 21× @SuppressWarnings("unchecked") — GSON deserialization casts (MappingData: 10, AttributeMapper: 5, MqRestSession: 6)
• 2× @SuppressWarnings("PMD.CloseResource") — justified resource lifecycle management

Test Code Inline (76)

• 76× @SuppressWarnings("unchecked") — all Mockito ArgumentCaptor.forClass(Map.class) type erasure

Actionable Items

1. Eliminate source code unchecked casts via Jackson (~2-3 hrs)

Switch JSON deserialization from GSON to Jackson with TypeReference:

// Before (GSON — requires unchecked cast)
Type mapType = new TypeToken<Map<String, Object>>() {}.getType();
Map<String, Object> data = GSON.fromJson(json, mapType);

// After (Jackson — type-safe, no cast needed)
ObjectMapper mapper = new ObjectMapper();
Map<String, Object> data = mapper.readValue(json,
    new TypeReference<Map<String, Object>>() {});

Jackson's generic-aware API eliminates the need for @SuppressWarnings("unchecked") at deserialization points.

Eliminates: ~15-21 source code suppressions
Adds: com.fasterxml.jackson.core:jackson-databind dependency

Not Actionable

• 76 test unchecked casts — Mockito's ArgumentCaptor.forClass() API uses Class<T> which cannot express generic types due to Java type erasure. This is an inherent Mockito limitation (verified against Mockito 5.21.0). Refactoring to inline verification would require 6-8 hours for marginal benefit.
• 2 PMD.CloseResource — both well-documented and correct (HttpClient lifecycle, InputStreamReader closure chain)
• 22 PMD rule exclusions — all justified (Design complexity rules for dispatcher methods, multithreading rules for managed HTTP clients, style rules for readability). Re-enabling would require 15-20 hours of refactoring with no quality improvement.
• 4 PMD threshold overrides — justified by mqscCommand() dispatcher complexity and 3-layer mapping pipeline
• Checkstyle/JaCoCo config exclusions — standard Java project patterns