[#10] Refactor: Optional.get() => Optional.orElseGet() 으로 변경 (피드백)

- 존재하지 않는 User의 경우 빈 User 객체를 생성함.
- User.matchPassword()에서 빈 객체인 경우를 고려하여 null 검사를 수행

BE/src/main/java/com/codesquad/team1/signup/controller/ApiUserController.java

@@ -8,7 +8,6 @@
 
 import javax.servlet.http.HttpSession;
 import java.security.InvalidParameterException;
-import java.util.Optional;
 
 @RestController
 @RequestMapping("/api/users")
@@ -48,11 +47,7 @@ public User createUser(@RequestBody User user) {
 
     @PostMapping("/login")
     public boolean login(@RequestBody User loginUser, HttpSession session) {
-        Optional<User> optionalUser = userRepository.findByUserId(loginUser.getUserId());
-        if (!optionalUser.isPresent())
-            return false;
-
-        User user = optionalUser.get();
+        User user = userRepository.findByUserId(loginUser.getUserId()).orElseGet(User::new);
         if (!user.matchPassword(loginUser))
             return false;
 

BE/src/main/java/com/codesquad/team1/signup/repository/User.java

@@ -94,6 +94,6 @@ public boolean validate() {
     }
 
     public boolean matchPassword(User loginUser) {
-        return this.password.equals(loginUser.password);
+        return this.password != null && this.password.equals(loginUser.password);
     }
 }