Question

我有两个表...一个贷款表和一个客户表。客户可以提供多笔贷款，但我想一次将客户限制为一笔有效贷款。在第一笔贷款完成之前，他们无法创建第二笔贷款（ loan.active = false ）

我已经这样设置了我的贷款表：

@Entity
public class Loan implements Serializable {

private static final long serialVersionUID = 0x62B6DA99AA12AAA8L;

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

@OneToOne(fetch = FetchType.LAZY)
private Customer customer;

@Column private String dateLoaned;
@Column private String dateToReturn;
@Column private String dateOfReturn;
@Column private Boolean active=false;

客户表如下：

@Entity
public class Customer implements Serializable {

private static final long serialVersionUID = 0x63A6DA99BC12A8A8L;

@Column @GeneratedValue(strategy = GenerationType.AUTO) @Id private Integer id;
@Column private String firstname;
@Column private String surname;
@Column private String address;
@Column private String town;
@Column private String postcode;
@Column (unique=true) private String personalnumber;
@Column (unique=true) private String emailaddress;


@OneToOne(fetch = FetchType.EAGER)
private Loan loan;

这使我可以与同一位客户创建新的贷款。到目前为止一切顺利。

我想进行查询，以查询客户是否已经有一笔有效的贷款。

到目前为止，我的贷款库是：

@Query("select loan_id from Loan l where l.customer.id = :customerId and l.active = true")
Boolean customerHasActiveLoan(@Param("customerId") Integer customerId);

这是正确的方法吗？

Answer 1

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对于该示例，等效于：

@Query

可以简化为

//Will return the active loan, if exists, or null
@Query("select l from Loan l where l.customer.id = :customerId and l.active = true")
public Loan getActiveLoad(@Param("customerId") Integer customerId)

有时public Local findOneByCustomerIdAndActiveIsTrue(Long id)方法可以生成长方法名称，因此，如果您愿意，可以使用method name注释

创建具有一对一关系的查询

1 个答案: