SpringJPA 簡單應用

在application.properties 裏面聲明
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5InnoDBDialect spring.jpa.hibernate.ddl-auto=update

model 類裏面跟數據庫對應的加上註解：

@Entity
@Table(name = "polls")
public class Poll extends UserDateAudit {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @NotBlank
    @Size(max = 140)
    private String question;

    @OneToMany(
            mappedBy = "poll",
            cascade = CascadeType.ALL,
            fetch = FetchType.EAGER,
            orphanRemoval = true
    )
    @Size(min = 2,max = 6)
    @Fetch(FetchMode.SELECT)
    @BatchSize(size = 30)
    private List<Choice> choices = new ArrayList<>();

    @NotNull
    private Instant expirationDateTime;
  //略去getter setter
  public void addChoice(Choice choice) {
        choices.add(choice);
        choice.setPoll(this);
    }

    public void removeChoice(Choice choice) {
        choices.remove(choice);
        choice.setPoll(null);
    }
}

簡單的CRUD就這樣

@Repository
public interface UserRepository extends JpaRepository<User,Long> {
    Optional<User> findByEmail(String email);

    Optional<User> findByUsernameOrEmail(String username,String email);

    List<User> findByIdIn(List<Long> userIds);

    Optional<User> findByUsername(String username);

    Boolean existsByUsername(String username);

    Boolean existsByEmail(String email);
}

負責的需要自己寫查詢SQL

@Repository
public interface VoteRepository extends JpaRepository<Vote,Long> {

    @Query("SELECT NEW com.example.polls.model.ChoiceVoteCount(v.choice.id,count(v.id)) FROM Vote v where v.poll.id in :pollIds GROUP BY v.choice.id")
    List<ChoiceVoteCount> countByPollIdInGroupByChoiceId(@Param("pollIds") List<Long> pollIds);

    @Query("SELECT NEW com.example.polls.model.ChoiceVoteCount(v.choice.id, count(v.id)) FROM Vote v WHERE v.poll.id = :pollId GROUP BY v.choice.id")
    List<ChoiceVoteCount> countByPollIdGroupByChoiceId(@Param("pollId") Long pollId);

    @Query("SELECT v FROM Vote v where v.user.id = :userId and v.poll.id in :pollIds")
    List<Vote> findByUserIdAndPollIdIn(@Param("userId") Long userId,@Param("pollIds") List<Long> pollIds);

    @Query("SELECT v FROM Vote v where v.user.id = :userId and v.poll.id = :pollId")
    Vote findByUserIdAndPollId(@Param("userId") Long userId,@Param("pollId") Long pollId);

    @Query("SELECT COUNT(v.id) from Vote v where v.user.id = :userId")
    long countByUserId(@Param("userId") Long userId);

    @Query("SELECT v.poll.id FROM Vote v WHERE v.user.id = :userId")
    Page<Long> findVotedPollIdsByUserId(@Param("userId") Long userId, Pageable pageable);
}

這樣就開啓了，在controller 裏注入即可使用

public class AuthController {

    @Autowired
    AuthenticationManager authenticationManager;
    
    @Autowired
    UserRepository userRepository;
    
    @Autowired
    RoleRepository roleRepository;
    
    @Autowired
    PasswordEncoder passwordEncoder;
    
    @PostMapping("/signup")
    public ResponseEntity<?> registerUser(@Valid @RequestBody SignUpRequest signUpRequest) {
        if (userRepository.existsByUsername(signUpRequest.getUsername())) {
            return  new ResponseEntity(new ApiResponse(false,"Username is already taken"),
                    HttpStatus.BAD_REQUEST);
        }

        if (userRepository.existsByEmail(signUpRequest.getEmail())) {
            return  new ResponseEntity(new ApiResponse(false,"Email Address already in use!"),
                    HttpStatus.BAD_REQUEST);
        }

        User user = new User(signUpRequest.getName(),signUpRequest.getUsername(),
                signUpRequest.getEmail(),signUpRequest.getPassword());

        user.setPassword(passwordEncoder.encode(user.getPassword()));

        Role userRole = roleRepository.findByName(RoleName.ROLE_USER)
                .orElseThrow(() -> new AppException("User Role not set"));

        user.setRoles(Collections.singleton(userRole));

        User result = userRepository.save(user);

        URI location = ServletUriComponentsBuilder
                .fromCurrentContextPath().path("/api/users/{username}")
                .buildAndExpand(result.getUsername()).toUri();

        return ResponseEntity.created(location).body(new ApiResponse(true,"User registered successfully"));
    }
}

這個就是SpringJPA 在項目裏的應用。

關於分頁，定義一個返回頁面的分頁類

public class PagedResponse<T> {

    private List<T> content;
    private int page;
    private int size;
    private long totalElements;
    private int totalPages;
    private boolean last;

    public PagedResponse() {}

    public PagedResponse(List<T> content, int page, int size, long totalElements, int totalPages, boolean last) {
        this.content = content;
        this.page = page;
        this.size = size;
        this.totalElements = totalElements;
        this.totalPages = totalPages;
        this.last = last;
    }
    //省略 getter setter
 } 

定義分頁常量類

public interface AppConstants {
    String DEFAULT_PAGE_NUMBER = "0";
    String DEFAULT_PAGE_SIZE = "30";

    int MAX_PAGE_SIZE = 50;
}

分頁

Pageable pageable = PageRequest.of(page,size, Sort.Direction.DESC,"createdAt");
Page<Poll> polls = pollRepository.findAll(pageable);