Spring数据JPA规范多对一关系

Question

我在Spring Data JPA中有两个实体：

User--->* TaxPayment 

目标是获取与user\u id相关的所有税款：

User.java

public class User extends AbstractAuditingEntity implements Serializable {

    private static final long serialVersionUID = 1L;

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

..........
}

税务ayment.jva

public class TaxPayment implements Serializable {

    private static final long serialVersionUID = 1L;

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

    @NotNull
    @Column(name = "payment_date", nullable = false)
    private LocalDate paymentDate;

    @NotNull
    @Column(name = "amount", precision=10, scale=2, nullable = false)
    private BigDecimal amount;

    @Column(name = "reference")
    private String reference;

    @ManyToOne
    private User user;

    public Long getId() {
        return id;
    }..
}

我不想要一个太多的注释从User.java和列映射在纳税user_id。

规格等级如下：

final class TaxPaymentSpecification {
    
    private TaxPaymentSpecification(){
        
    }
    
    static Specification<TaxPayment> hasUser(Long userId){
        return new Specification<TaxPayment>() {
            
            @Override
            public Predicate toPredicate(Root<TaxPayment> arg0, CriteriaQuery<?> arg1,
                    CriteriaBuilder arg2) {
                // TODO Auto-generated method stub
                Root<TaxPayment> root = arg0;
                Subquery<Long> subqry =  arg1.subquery(Long.class);
                Root<User> user =  subqry.from(User.class);
                
                final Join<User,TaxPayment> taxpays = root.join("user");
                
                subqry.select(taxpays.<Long> get("user_id"));
                
                subqry.where(arg2.equal(user.<Long> get("id"),userId));
                return arg2.in(arg0.get("user_id")).value(subqry);

           }
        };
        
    }
}

根据我获取所有与user\u id相关的税款的目标，规范是正确的还是错误的？

Answer 1

如果您已经知道userId，则不需要使用子查询，它将是user_id的值：

@Override
public Predicate toPredicate(Root<TaxPayment> arg0, CriteriaQuery<?> arg1, 
        CriteriaBuilder arg2) {
  return arg2.equal(arg0.get("user_id"), userId);
}