System Bug Fixer Skill

1. Objective

To rapidly identify, isolate, and resolve system anomalies such as:

• Service startup failures (Port conflicts, DB connection errors)
• Persistent “Ghost” Data (Menu items that won’t disappear)
• Logic inconsistencies between Frontend and Backend
• Caching issues (Redis, Browser, Vuex)

2. Methodology

Phase 1: The Health Check (Stop & Clear)

Before debugging a weird issue, ensure the environment is clean.

1. Kill Zombie Processes:

   taskkill /F /IM java.exe
   

2. Clear Ports: Check if 8080/6379 are truly free.
3. Restart Middleware: Restart Redis/MySQL if data seems “stuck”.
4. Flush Logs: Rename backend.log (e.g., backend.log.old) to ensure you are reading fresh logs.

Phase 2: Deep Log Analysis

Do not trust the UI. Trust the Logs.

1. Enable Debug Logging:
   • Add log.info("DEBUG_TRACE: Variable={}", var) in critical logical paths.
   • If utilizing MyBatis, inspect the ==> Preparing: SQL output.
2. Result Verification:
   • Does <== Total: 0 match your expectation?
   • Did the code actually reach your log.info? If not, check try-catch blocks swallowing exceptions.

Phase 3: Data Integrity Verification

Code is often correct, but Data is wrong.

1. Direct DB Query: Use MySQL CLI/Workbench to query the raw data.
   • Example: SELECT * FROM sys_menu WHERE menu_name LIKE '%Cart%';
   • Compare menu_id in DB vs Code Hardcoding.
2. Cache vs Source:
   • Redis: FLUSHALL (in Dev) to rule out stale permissions.
   • User Permissions: Logout and Re-login to refresh Subject principal.

Phase 4: The “Nuclear” Option (Hardcoding & Isolation)

If logic seems inexplicably skipped:

1. Isolate: Create a localized test case (e.g., a specific if block).
2. Hardcode: Temporarily hardcode IDs to confirm control.
   • Example: if (id == 2021) remove();
3. Broaden Scope: Use toLowerCase() and .contains() instead of equals().

3. Common Fix Patterns (RuoYi Specific)

Menu/Permission Persistence

• Symptom: Menu visible after Role revocation.
• Fix: Check SysMenuServiceImpl.selectMenuTreeByUserId. Ensure getChildPerms isn’t caching an old tree. Force backend restart.

Port In Use (8080)

• Symptom: “Web server failed to start”.
• Fix:

  netstat -ano | findstr :8080
  taskkill /PID <PID> /F
  

Frontend Not Updating

• Symptom: Code changed, UI stuck.
• Fix: npm run build:prod might be needed if not running dev. Disable Browser Cache (DevTools -> Network -> Disable Cache).

4. Verification

After applying a fix:

1. Clean Start: Restart backend.
2. Clean Login: Logout -> Clear Browser Cache -> Login.
3. Log Confirmation: Verify the specific log entry for the fix appears.