java - 如何在 Spring Boot 中使用 CommandLineRunner？

Question

我尝试通过CommandLineRunner接口(interface)将数据设置到数据库。

如果我删除有关银行实例的所有内容并使用空银行列表保存帐户，它会将数据保存到数据库中。

带有 CommandLineRunner 的 Bean 类:

@Override
    public void run(String... args) throws Exception {
        List<Bank> banks = new ArrayList<>();
        Bank bank = new Bank("Приват Банк", 5000.0f);
        Bank bank2 = new Bank("UkrsibBank", 3000.1f);
        banks.add(bank);
        banks.add(bank2);
        bankAccountRepository.save(bank);
        bankAccountRepository.save(bank2);
        Account account = new Account(15000.2f, 1200.5f,  banks);
        accountRepository.save(account);
    }

我的实体:

@Entity
@Data
@NoArgsConstructor
public class Account {

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

    @Column(name = "total_balance")
    private float totalBalance;

    private float cash;

    @OneToMany(cascade = CascadeType.ALL)
    @JoinTable(name = "account_banks", joinColumns = @JoinColumn(name = "account_id"),
            inverseJoinColumns = @JoinColumn(name = "bank_id") )
    private List<Bank> banks;

    public Account(float totalBalance, float cash, List<Bank> banks) {
        this.totalBalance = totalBalance;
        this.cash = cash;
        this.banks = banks;
    }
}

@Entity
@Data
@NoArgsConstructor
public class Bank implements Serializable {

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

    private String name;
    @Column(name = "account_balance")
    private float balance;

    public Bank(String name, float balance) {
        this.name = name;
        this.balance = balance;
    }
}

我的错误是什么？堆栈跟踪:

java.lang.IllegalStateException: Failed to execute CommandLineRunner
Caused by: org.springframework.dao.InvalidDataAccessApiUsageException: detached entity passed to persist: 
Caused by: org.hibernate.PersistentObjectException: detached entity passed to persist:

Answer 1

您将此关系的级联类型设置为 cascade = CascadeType.ALL当您调用accountRepository.save(account)时Hibernate 尝试保留其相关实体(Bank)，但在此之前，您还手动保存了它们(之后它们处于分离状态)。这会导致错误。我认为有以下三种可能的解决方案:

• 如果您想独立保留实体，请完全删除级联策略。
• 坚持Bank实体传递地与 Account

Bank bank = new Bank("Приват Банк", 5000.0f);
        Bank bank2 = new Bank("UkrsibBank", 3000.1f);
        banks.add(bank);
        banks.add(bank2);
        Account account = new Account(15000.2f, 1200.5f,  banks);
        accountRepository.save(account);

• 装饰方法run与 @Transactional注解以保证您的实体处于持久状态