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.

• Kill Zombie Processes: taskkill /F /IM java.exe

• Clear Ports: Check if 8080/6379 are truly free.

• Restart Middleware: Restart Redis/MySQL if data seems "stuck".

• 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.

• Enable Debug Logging:

• Add log.info("DEBUG_TRACE: Variable={}", var) in critical logical paths.

• If utilizing MyBatis, inspect the ==> Preparing: SQL output.

• 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.

• 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.

• 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:

• Isolate: Create a localized test case (e.g., a specific if block).

• Hardcode: Temporarily hardcode IDs to confirm control.

• Example: if (id == 2021) remove();

• 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:

• Clean Start: Restart backend.

• Clean Login: Logout -> Clear Browser Cache -> Login.

• Log Confirmation: Verify the specific log entry for the fix appears.