spring + hibernate为什么多对多的关系不会持久？

Question

我有一个实体E1定义为

@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定义为

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

和控制器定义为

实体

@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是扩展JpaRepository@Repository注释接口并有空的身体）。

，当我通过我的调试器c方法步骤，我看到最后两行em.refresh后，无论是e1和e2有自己的电视机清除。

基于我对堆栈溢出发现的其他问题，我试图定义E2为

@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<>(); 
} 

但这并没有帮助。

原始质询（来自之前我试图测试上面的简化的情况） 我有一个类Robot定义类似于以下：

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

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

和类Match类似于

@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<>(); 

和类别Result定义类似于

@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; 
} 

并尝试保存的关系如下：

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是实现JpaRepository弹簧创建的Bean。 运行此代码时，插入语句在result对象（hibernate会将其所有sql命令输出到控制台）的休眠状态下运行，但没有一个用于“match_robot”表。我不应该说，这个段之前，result是在Hibernate实体生命周期的过渡状态，match是在持久状态，robot是在持久状态，result的match和robot属性已设置为match和robot分别。

基于堆栈溢出和其他网站的其他问题，我也试图定义匹配变量

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

这并没有帮助。除此之外，我看到的唯一建议是确保在多方关系中两个实体在坚持之前彼此保持一致，但据我所知，我在这里这样做。

我该如何坚持这种关系？

编辑：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()不刷新对数据库的更改。有必要使用JpaRepository.flush()或JpaRepository.saveAndFlush()来清除更改。