Javaã®é€²åŒ–ã«ã¨ã‚‚ãªã†é‹ç”¨æ€§ã®å‘上ã¯ã‚·ã‚¹ãƒ†ãƒ è¨è¨ˆã«ã©ã†ã„ã†å¤‰åŒ–ã‚’ã‚‚ãŸã‚‰ã™ã®ã‹8. NullPointerExceptionã®å…¸åž‹ä¾‹ HttpSession session = request.getSession(); User user = session.getAttribute("user"); if (user.isAdmin()) { // ... } ã“ã“ã§NullPointerException発生 引数ãªã—ã§getSessionを呼ã¶ã®ã§ã‚»ãƒƒã‚·ãƒ§ãƒ³ãŒãªã„ å ´åˆã¯ç©ºã®ã‚‚ã®ãŒä½œã‚‰ã‚Œã‚‹ 空ã®Sessionã®å ´åˆã€userã¯nullã«ãªã‚‹ã€‚ 9. Guard against null HttpSession session = request.getSession(false); if (session == null) { response.sendRedirect(LOGIN_URL); return; } User user = session.ge
{{#tags}}- {{label}}
{{/tags}}