spring + hibernate爲什麼多對多的關係不會持久？

Question

我有一個實體E1定義爲

@Entity 
public class E1 { 
    @Id 
    @GeneratedValue 
    public long id; 
    @ManyToMany(cascade={CascadeType.PERSIST, CascadeType.MERGE}) 
    @JoinTable(
      name="e1_e2", 
      joinColumns = @JoinColumn(name = "e2_id"), 
      inverseJoinColumns = @JoinColumn(name = "e1_id") 
    ) 
    public Set<E2> e2s = new HashSet<>(); 
} 

E2定義爲

@Entity 
public class E2 { 
    @Id 
    @GeneratedValue 
    public long id; 
    @ManyToMany(mappedBy = "e2s") 
    public Set<E1> e1s = new HashSet<>(); 
} 

和控制器定義爲

實體

@RestController 
@RequestMapping("/") 
public class C1 { 
    private final E1Repository e1Repository; 
    private final E2Repository e2Repository; 

    @PersistenceContext 
    EntityManager em; 

    @Autowired 
    public C1(E1Repository e1Repository, E2Repository e2Repository) { 
     this.e1Repository = e1Repository; 
     this.e2Repository = e2Repository; 
    } 

    @Transactional 
    @RequestMapping(method = POST) 
    public void c(){ 
     E1 e1 = new E1(); 
     E2 e2 = new E2(); 

     e1Repository.save(e1); 
     e2Repository.save(e2); 

     em.refresh(e1); 
     em.refresh(e2); 

     e1.e2s.add(e2); 
     e2.e1s.add(e1); 

     e1Repository.save(e1); 
     e2Repository.save(e2); 

     em.refresh(e1); 
     em.refresh(e2); 
    } 

} 

（E1Repository和E2Repository是擴展JpaRepository@Repository註釋接口並有空的身體）。

，當我通過我的調試器c方法步驟，我看到最後兩行em.refresh後，無論是e1和e2有自己的電視機清除。

基於我對堆棧溢出發現的其他問題，我試圖定義E2爲

@Entity 
public class E2 { 
    @Id 
    @GeneratedValue 
    public long id; 
    @ManyToMany(cascade = CascadeType.PERSIST) 
    @JoinTable(
      name="e1_e2", 
      inverseJoinColumns = @JoinColumn(name = "e2_id"), 
      joinColumns = @JoinColumn(name = "e1_id") 
    ) 
    public Set<E1> e1s = new HashSet<>(); 
} 

但這並沒有幫助。

原始質詢（來自之前我試圖測試上面的簡化的情況） 我有一個類Robot定義類似於以下：

@Entity 
class Robot{ 
    @Id 
    @GeneratedValue 
    private long id; 

    @ManyToMany(mappedBy="robots") 
    private Set<Match> matches = new HashSet<>(); 
} 

和類Match類似於

@Entity 
class Robot{ 
    @Id 
    @GeneratedValue 
    private long id; 
    @ManyToMany(cascade={CascadeType.Persist,CascadeType.Merge}) 
    @JoinTable(
     name = "match_robot", 
     joinColumns = {@JoinColumn(name = "Match_id")}, 
     inverseJoinColumns = {@JoinColumn(name = "Robot_id")} 
) 
private Set<Robot> robots = new HashSet<>(); 

和類別Result定義類似於

@Entity 
public class Result { 
    @Id 
    @GeneratedValue 
    private long id; 

    @ManyToOne(optional = false) 
    private Match match; 

    @ManyToOne(optional = false) 
    @NotNull(groups = {Default.class, Creating.class}) 
    private Robot robot; 
} 

並嘗試保存的關係如下：

resultRepository.save(result); 
match.getRobots().add(result.getRobot()); 
result.getRobot().getMatches().add(match); 
robotRepository.save(result.getRobot()); 
matchRepository.save(match); 
entityManager.refresh(result); 
entityManager.refresh(result.getRobot()); 
entityManager.refresh(match); 

其中*Repository是實現JpaRepository彈簧創建的Bean。 運行此代碼時，插入語句在result對象（hibernate會將其所有sql命令輸出到控制檯）的休眠狀態下運行，但沒有一個用於「match_robot」表。我不應該說，這個段之前，result是在Hibernate實體生命週期的過渡狀態，match是在持久狀態，robot是在持久狀態，result的match和robot屬性已設置爲match和robot分別。

基於堆棧溢出和其他網站的其他問題，我也試圖定義匹配變量

@ManyToMany(cascade = CascadeType.PERSIST) 
@JoinTable(
     name = "match_robot", 
     inverseJoinColumns = {@JoinColumn(name = "Match_id")}, 
     joinColumns = {@JoinColumn(name = "Robot_id")} 
) 
private Set<Match> matches = new HashSet<>(); 

這並沒有幫助。除此之外，我看到的唯一建議是確保在多方關係中兩個實體在堅持之前彼此保持一致，但據我所知，我在這裏這樣做。

我該如何堅持這種關係？

編輯：上下文完整的方法：

@Transactional 
@RequestMapping(value = "/{match:[0-9]+}/results", method = RequestMethod.POST) 
public ResultResource createResult(@PathVariable Match match, 
            @Validated(Result.Creating.class) 
            @RequestBody Result result) { 
    if (match == null) throw new ResourceNotFoundException(); 

    result.setScorecard(scorecardRepository 
      .findById(result.getScorecard().getId())); 
    if (result.getScorecard() == null) { 
     throw new ScorecardDoesNotExistException(); 
    } 

    result.setMatch(match); 

    //remove null scores 
    result.getScores().removeIf(
      fieldResult -> fieldResult.getScore() == null 
    ); 

    //replace transient robot with entity from database 
    Robot existingRobot = robotRepository 
      .findByNumberAndGame(result.getRobot().getNumber(),result.getRobot().getGame()); 
    if (existingRobot == null) { //create new robot 
     //find team for this robot 
     Team existingTeam = teamRepository 
       .findByNumberAndGameType(
         result.getRobot().getNumber(), 
         result.getScorecard().getGame().getType()); 
     if (existingTeam == null) { 
      Team team = new Team(); 
      team.setNumber(result.getRobot().getNumber()); 
      team.setGameType(result.getMatch().getEvent().getGame().getType()); 
      team.setDistrict(result.getMatch().getEvent().getDistrict()); 
      teamRepository.save(team); 
      result.getRobot().setTeam(team); 
     } 
    else result.getRobot().setTeam(existingTeam); 
      result.getRobot().setGame(result.getMatch().getEvent().getGame()); 

     robotRepository.save(result.getRobot()); 
     entityManager.refresh(result.getRobot()); 
    } else result.setRobot(existingRobot); 
    List<Robot> all = robotRepository.findAll(); 

    //replace transient FieldSections with entities from database 
    //todo: reduce database hits 
    //noinspection ResultOfMethodCallIgnored 
    result.getScores().stream() 
      .peek(fieldResult -> fieldResult.setField(
        fieldSectionRepository.findByIdAndScorecard(
          fieldResult.getField().getId(), 
          result.getScorecard()))) 
       .peek(fieldResult -> { 
       if (fieldResult.getField() == null) 
        throw new ScoresDoNotExistException(); 
      }) 
      .forEach(fieldResult->fieldResult.setResult(result)); 


    if (!result.scoresMatchScorecardSections()) { 
     throw new ScoresDoNotMatchScorecardException(); 
    } 

    if (!result.allMissingScoresAreOptional()) { 
     throw new RequiredScoresAbsentException(); 
    } 

    if (!result.gameMatchesScorecard()) { 
     throw new GameDoesNotMatchScorecardException(); 
    } 

    resultRepository.save(result); 
    match.getRobots().add(result.getRobot()); 
    result.getRobot().getMatches().add(match); 
    robotRepository.save(result.getRobot()); 
    matchRepository.save(match); 
    entityManager.refresh(result); 
    entityManager.refresh(result.getRobot()); 
    entityManager.refresh(match); 
    return new ResultResourceAssembler().toResource(result); 
} 

Answer 1

JpaRepository.save()不刷新對數據庫的更改。有必要使用JpaRepository.flush()或JpaRepository.saveAndFlush()來清除更改。