fix: reduce thread blocking by double null check in invokeMethod()

[lukaszlenart]

Summary

Cherry-pick of PR #521 adapted for Java 8 compatibility.

• Implements double-null-check pattern for _methodAccessCache and _methodPermCache
• Avoids synchronizing on Method objects when cache values already exist
• Reduces thread contention in high-concurrency scenarios

Problem

Production environments experienced severe thread blocking (980+ threads blocked) waiting to acquire locks on java.lang.reflect.Method objects in OgnlRuntime.invokeMethod(). The root cause was that all threads competed for the same Method monitor even when cache values already existed.

Solution

Move cache check outside the synchronized block (first null check), then re-check inside if null (double null check). This eliminates unnecessary synchronization when the cache is already populated.

Key Adaptations for Java 8

• Kept method.isAccessible() instead of Java 9+ method.canAccess()
• Preserved full securityManager logic for _methodPermCache
• No var usage (explicit types only)

Test plan

• All 993 tests pass (./mvnw clean test)
• Verified Java 8 compatibility

🤖 Generated with Claude Code

[sonarqubecloud]

Quality Gate failed

Failed conditions
C Maintainability Rating on New Code (required ≥ A)
C Reliability Rating on New Code (required ≥ A)

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