Java 通过JPA更新对象并获取旧值

我想记录帐户的更改。因此，我创建了一个实体类来记录更改。 每次保存或更新帐户实体时，都会创建一个日志记录对象

当使用新余额更新对象时，应从数据库中检索旧余额。 由于对象绑定到会话，因此检索其旧平衡并不容易，因为总是会获得新平衡

为了避免这种情况，我将对象与会话分离。然而，这似乎是一个应该避免的解决办法

以下代码片段将说明该场景

非常感谢您的任何建议

测试：

public class AccountServiceTest
{
    @Autowired
    AccountService        accountService;

    @Autowired
    ChangeAccountService  changeAccountService;

    @Test
    public void shouldHaveChangeLog()
    {
        Account account = this.accountService.updateAccount(new Account(0, 10.0));
        assertThat(account.getId(), is(not(0L)));

        account.setBalance(20.0);
        account = this.accountService.updateAccount(account);

        final List<ChangeAccountLog> changeResultLogs = this.changeAccountService.findAll();
        assertThat(changeResultLogs.get(1).getNewBalance(), is(not(changeResultLogs.get(1).getOldBalance())));
    }
}

日志类的服务：

@Service
public class ChangeAccountService
{
    @Autowired
    AccountService                accountService;

    @Autowired
    ChangeAccountLogRepository    repository;

    public ChangeAccountLog save(final ChangeAccountLog changeAccountLog)
    {
        return this.repository.save(changeAccountLog);
    }

    public List<ChangeAccountLog> findAll()
    {
        return this.repository.findAll();
    }

    public ChangeAccountLog saveLog(final Account account)
    {
        final Double oldAccountBalance = oldAccountBalance(account);
        final Double newAccountBalance = account.getBalance();
        final ChangeAccountLog changeAccountLog = new ChangeAccountLog(0, oldAccountBalance, newAccountBalance);

        return this.repository.save(changeAccountLog);
    }

    @PersistenceContext
    EntityManager   em;

    private Double oldAccountBalance(final Account account)
    {
        this.em.detach(account);

        final Account existingAccount = this.accountService.findById(account.getId());

        if (existingAccount != null)
        {
            return existingAccount.getBalance();
        }
        return null;

    }
}

@Data
@NoArgsConstructor
@AllArgsConstructor
@Entity
public class ChangeAccountLog
{
     @Id
     @GeneratedBalance
     private long     id;

     private Double    oldBalance;
     private Double    newBalance;
}

日志记录类：

@Service
public class ChangeAccountService
{
    @Autowired
    AccountService                accountService;

    @Autowired
    ChangeAccountLogRepository    repository;

    public ChangeAccountLog save(final ChangeAccountLog changeAccountLog)
    {
        return this.repository.save(changeAccountLog);
    }

    public List<ChangeAccountLog> findAll()
    {
        return this.repository.findAll();
    }

    public ChangeAccountLog saveLog(final Account account)
    {
        final Double oldAccountBalance = oldAccountBalance(account);
        final Double newAccountBalance = account.getBalance();
        final ChangeAccountLog changeAccountLog = new ChangeAccountLog(0, oldAccountBalance, newAccountBalance);

        return this.repository.save(changeAccountLog);
    }

    @PersistenceContext
    EntityManager   em;

    private Double oldAccountBalance(final Account account)
    {
        this.em.detach(account);

        final Account existingAccount = this.accountService.findById(account.getId());

        if (existingAccount != null)
        {
            return existingAccount.getBalance();
        }
        return null;

    }
}

@Data
@NoArgsConstructor
@AllArgsConstructor
@Entity
public class ChangeAccountLog
{
     @Id
     @GeneratedBalance
     private long     id;

     private Double    oldBalance;
     private Double    newBalance;
}

---

您可能希望使用Hibernate Envers创建版本控制表，而不是创建单独的日志对象。

这是一个好建议，但传统应用程序提供了一个给定的表结构。与其查询它，不如将帐户实体中的旧余额缓存在临时字段中，并在从中创建ChangeAccountLog时清除它。