Java8optional.map.orElse正在执行orElse部分[重复]

Question

@PostMapping(path = "/addUser", consumes = MediaType.APPLICATION_JSON_VALUE, produces = MediaType.APPLICATION_JSON_VALUE)
    public ResponseEntity<Response> addUser(@RequestBody User user){
        
        user = userService.checkIfUserExsits(user.getEmail())
                          .map(usr -> usr)
                          .orElse(userService.persistUser(user));
        
        return respHelpers.prepareSuccessResponse(user,"Processed");                                       
    }

public Optional<User> checkIfUserExsits(String email){      
    Optional<User> user = Optional.ofNullable(userRepo.findByEmail(email));     
    return user;
}

@Repository
public interface UserRepo extends JpaRepository<User, UUID> {

    public User findByEmail(String email); 

}

Answer 1

orelse()是一个方法，当您调用该方法时，它的参数会在它的主体执行之前得到计算。因此，始终执行userservice.persistuser(user)。

您应该使用orelseget:

    user = userService.checkIfUserExsits(user.getEmail())
                      .map(usr -> usr)
                      .orElseGet(() -> userService.persistUser(user));

这样，只有当可选的为空时，lambda表达式的主体才会执行。