🛑️ Stop Using ThreadLocal! Migrate to Java Scoped Values

ThreadLocal worked great for traditional threads — but with Java 21's Virtual Threads, it causes memory bloat and mutable state chaos. Java's Scoped Values (JEP 506) fix this: immutable, memory-efficient, and designed for modern concurrency. This 13-minute migration guide shows you how to replace ThreadLocal with Scoped Values step-by-step.

🎯 What You'll Learn:
• Why ThreadLocal breaks down with Virtual Threads (memory footprint explosion)
• How Scoped Values provide immutable, bounded-lifetime context sharing
• Step-by-step migration: ThreadLocal → Scoped Values API
• Code examples: Before/After comparison with real use cases
• When to use Scoped Values vs when ThreadLocal is still valid
• Integration with Structured Concurrency and Project Loom
• Testing strategies for migrated code

⏱️ Timestamps:
00:00 - Intro
00:20 - ThreadLocal Problems
00:40 - Trace Filter with ThreadLocal
03:20 - ThreadLocal Problems
04:40 - Testing it
07:20 - Migration to ScopeValue
12:30 - Outro

💡 Key Takeaway: Scoped Values eliminate ThreadLocal's memory leaks and mutability issues in Virtual Thread environments. Perfect for web request context, user sessions, database transactions — anything you'd share across thread boundaries!

✨ Java Features Used:
• ScopedValue API (JEP 506 - finalized in Java 25)
• Virtual Threads (JEP 444 - Java 21+)
• Structured Concurrency integration (JEP 462)
• Immutable context propagation patterns

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📚 Official Resources:
• JEP 506 - Scoped Values: https://openjdk.org/jeps/506
• Oracle Scoped Values Guide: https://docs.oracle.com/en/java/javas...
• Project Loom Documentation: https://openjdk.org/projects/loom/

#java #java21 #scopedvalues #threadlocal #virtualthreads #projectloom #jep506 #concurrency

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