This post was migrated from Tistory. You can find the original here. Circular Reference Suppose we have the ERD shown above. When we call findAll on registered books, a problem occurs. List&...

This post was migrated from Tistory. You can find the original here. Comparison ArrayList<Integer> arrayList = new ArrayList<>(); LinkedList<Integer> linkedList...

This post was migrated from Tistory. You can find the original here. ArrayList private static final Object[] DEFAULTCAPACITY_EMPTY_ELEMENTDATA = {}; public ArrayList() { this.el...

This post was migrated from Tistory. You can find the original here. DTO/Lombok @Getter public class UserSignUpDto { ... private boolean admin = false; ... } For a boolean field, @...

This post was migrated from Tistory. You can find the original here. Filter This is Spring’s life cycle. Security Spring Security is also made up of a lot of filters. The purpose of Secu...

This post was migrated from Tistory. You can find the original here. ExceptionHandler @ExceptionHandler(IllegalArgumentException.class) public ResponseEntity<ExceptionResponseDto> ...

This post was migrated from Tistory. You can find the original here. RequestParam (1) @PostMapping("/test3") public String p2(@RequestParam PostRequestDto requestDto) { System.ou...

This post was migrated from Tistory. You can find the original here. combination static List<List<Integer>> combination(List<Integer> list, List<Integer> result, int ...

This post was migrated from Tistory. You can find the original here. You combine from, order by, and group by with commas. select * from A, B select course_id, week, count(c.likes) from checkin...

This post was migrated from Tistory. You can find the original here. concept IoC Inversion of Control public class A{ b = new B(); } In code like the above, A creates b directly itself. ...