JPA使用中应注意的地方

• ​​写在前面​​
• ​​一、事务处理​​
• ​​二、保存和批量保存​​
• ​​三、SQL日志打印问题​​

写在前面

一、事务处理

@Transactional，这个注解，想要关联事务处理，要特别注意异常处理

二、保存和批量保存

关于JPA中save,saveAndFlush和saveAll的区别，

@Transactional
  public <S extends T> S save(S entity) {
    if (entityInformation.isNew(entity)) {
      em.persist(entity);
      return entity;
    } else {
      return em.merge(entity);
    }
  }      

@Transactional
  public <S extends T> S saveAndFlush(S entity) {
    S result = save(entity);
    flush();
    return result;
  }      

@Transactional
  public <S extends T> List<S> saveAll(Iterable<S> entities) {
    Assert.notNull(entities, "The given Iterable of entities not be null!");
    List<S> result = new ArrayList<S>();
    for (S entity : entities) {
      result.add(save(entity));
    }
    return result;
  }      

// 测试，耗时约 130-170 s
 @GetMapping("/batch-add")
    public ResultBean batchAdd() {

        LocalDateTime start = LocalDateTime.now();
        for (int i = 60000; i < 61000; i++) {
            UserInfo u = new UserInfo();
            u.setUserName("name" + i);
            u.setUserCode("code" + i);
            userRepository.save(u);
        }
        LocalDateTime end = LocalDateTime.now();
        return ResultBean.ok(ChronoUnit.SECONDS.between(start,end));
    }
//  测试，耗时约 1 s
    @GetMapping("/batch-all")
    public ResultBean batchAllAdd() {

        ArrayList<UserInfo> list = Lists.newArrayList();
        LocalDateTime start = LocalDateTime.now();
        for (int i = 61000; i < 62000; i++) {
            UserInfo u = new UserInfo();
            u.setUserName("name" + i);
            u.setUserCode("code" + i);
            list.add(u);
        }
        userRepository.saveAll(list);
        LocalDateTime end = LocalDateTime.now();
        return ResultBean.ok(ChronoUnit.SECONDS.between(start, end));
    }      

三、SQL日志打印问题