Java Eager-fetch在hibernate中执行左连接，但在springboot/JPA中触发单独的sql查询

我看到很多文章中，在hibernate中，eagerfetch执行子表和父表的左连接。但当我使用springboot时，hibernate会触发单独的sql查询——这意味着一个select查询用于父表，一个select查询用于子表。为什么会有区别？springboot有没有升级，或者是我做错了什么

以下是我正在使用的实体：

订单实体：

@Entity
@Table(name="Ordertable", schema="cf_2583f365_c3c6_499a_a60d_138e7e7023eb")

public class Order {

@Id
@Column(name = "ORDER_ID")
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int orderId;


@Column(name = "DAT_SRC_ID")
private String dataSourceId;

@ManyToOne(fetch=FetchType.EAGER)
@JoinColumn(name = "ORDER_CUSTOMER_ID", referencedColumnName = "CUSTOMER_ID") 
private Customer customer;
}

@Entity
@Table(name="Customer", schema="cf_2583f365_c3c6_499a_a60d_138e7e7023eb")
public class Customer {

    @Id
    @Column(name = "CUSTOMER_ID")
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Long customerId;

    @Column(name = "CUSTOMER_NAME")
    private String customer_name;


    @Column(name = "CUSTOMER_address_id")
    private int customer_address_id;

    @Column(name = "DAT_SRC_ID")
    private String dataSourceId;

    @OneToMany(fetch=FetchType.EAGER)
    @JoinColumn(name = "ORDER_CUSTOMER_ID", referencedColumnName = "CUSTOMER_ID") 
    private List<Order> order;

}

@Entity
@Table(name="Customer", schema="cf_2583f365_c3c6_499a_a60d_138e7e7023eb")
public class Customer {
    @OneToMany(fetch=FetchType.EAGER)
    @JoinColumn(name = "ORDER_CUSTOMER_ID", referencedColumnName = "CUSTOMER_ID")
    @Fetch(FetchMode.JOIN)
    private List<Order> order;
}

@Entity
@Table(name="Ordertable", schema="cf_2583f365_c3c6_499a_a60d_138e7e7023eb")
public class Order {
    @JsonIgnore
    @ManyToOne()
    @JoinColumn(name = "ORDER_CUSTOMER_ID", referencedColumnName = "CUSTOMER_ID") 
    @Fetch(FetchMode.JOIN)
    private Customer customer;
}

客户实体：

@Entity
@Table(name="Ordertable", schema="cf_2583f365_c3c6_499a_a60d_138e7e7023eb")

public class Order {

@Id
@Column(name = "ORDER_ID")
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int orderId;


@Column(name = "DAT_SRC_ID")
private String dataSourceId;

@ManyToOne(fetch=FetchType.EAGER)
@JoinColumn(name = "ORDER_CUSTOMER_ID", referencedColumnName = "CUSTOMER_ID") 
private Customer customer;
}

@Entity
@Table(name="Customer", schema="cf_2583f365_c3c6_499a_a60d_138e7e7023eb")
public class Customer {

    @Id
    @Column(name = "CUSTOMER_ID")
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Long customerId;

    @Column(name = "CUSTOMER_NAME")
    private String customer_name;


    @Column(name = "CUSTOMER_address_id")
    private int customer_address_id;

    @Column(name = "DAT_SRC_ID")
    private String dataSourceId;

    @OneToMany(fetch=FetchType.EAGER)
    @JoinColumn(name = "ORDER_CUSTOMER_ID", referencedColumnName = "CUSTOMER_ID") 
    private List<Order> order;

}

@Entity
@Table(name="Customer", schema="cf_2583f365_c3c6_499a_a60d_138e7e7023eb")
public class Customer {
    @OneToMany(fetch=FetchType.EAGER)
    @JoinColumn(name = "ORDER_CUSTOMER_ID", referencedColumnName = "CUSTOMER_ID")
    @Fetch(FetchMode.JOIN)
    private List<Order> order;
}

@Entity
@Table(name="Ordertable", schema="cf_2583f365_c3c6_499a_a60d_138e7e7023eb")
public class Order {
    @JsonIgnore
    @ManyToOne()
    @JoinColumn(name = "ORDER_CUSTOMER_ID", referencedColumnName = "CUSTOMER_ID") 
    @Fetch(FetchMode.JOIN)
    private Customer customer;
}

存储库：

public interface CustomerRepository extends JpaRepository<Customer,Long> {

    public Customer findByCustomerId(Long customerId); 

}

编辑：这是否与@fetchmode.JOIN相关-链接：

为了检查FetchMode.JOIN是否有效，我在实体中添加了FetchMode.JOIN，如下所示，但JOIN查询仍然没有成功：

客户实体：

@Entity
@Table(name="Ordertable", schema="cf_2583f365_c3c6_499a_a60d_138e7e7023eb")

public class Order {

@Id
@Column(name = "ORDER_ID")
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int orderId;


@Column(name = "DAT_SRC_ID")
private String dataSourceId;

@ManyToOne(fetch=FetchType.EAGER)
@JoinColumn(name = "ORDER_CUSTOMER_ID", referencedColumnName = "CUSTOMER_ID") 
private Customer customer;
}

@Entity
@Table(name="Customer", schema="cf_2583f365_c3c6_499a_a60d_138e7e7023eb")
public class Customer {

    @Id
    @Column(name = "CUSTOMER_ID")
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Long customerId;

    @Column(name = "CUSTOMER_NAME")
    private String customer_name;


    @Column(name = "CUSTOMER_address_id")
    private int customer_address_id;

    @Column(name = "DAT_SRC_ID")
    private String dataSourceId;

    @OneToMany(fetch=FetchType.EAGER)
    @JoinColumn(name = "ORDER_CUSTOMER_ID", referencedColumnName = "CUSTOMER_ID") 
    private List<Order> order;

}

@Entity
@Table(name="Customer", schema="cf_2583f365_c3c6_499a_a60d_138e7e7023eb")
public class Customer {
    @OneToMany(fetch=FetchType.EAGER)
    @JoinColumn(name = "ORDER_CUSTOMER_ID", referencedColumnName = "CUSTOMER_ID")
    @Fetch(FetchMode.JOIN)
    private List<Order> order;
}

@Entity
@Table(name="Ordertable", schema="cf_2583f365_c3c6_499a_a60d_138e7e7023eb")
public class Order {
    @JsonIgnore
    @ManyToOne()
    @JoinColumn(name = "ORDER_CUSTOMER_ID", referencedColumnName = "CUSTOMER_ID") 
    @Fetch(FetchMode.JOIN)
    private Customer customer;
}

findByCustomerId实际上将基于该方法而不是使用em.find生成查询。它将按照从Customer c中选择c的方式创建一些内容，其中c.customerId=：customerId。之后，它将注意到fetch策略并获得所需的引用。这也得到了解释。查询将严格执行您指示它执行的操作

如果您想要急切地加载引用，您需要自己编写查询，沿着SELECT c FROM Customer c JOIN FETCH c.orders o其中c.customerId=：customerId的行，这将自动检索订单

---

然而，customerId实际上是实体的主键或标识符，因此根据Spring数据JPA版本，您应该实际使用findById或findOne方法。这将使用应考虑映射信息并创建适当查询的

供我参考-customerId是实际id，如果使用findById或findOne会发生什么情况，具体取决于所使用的Spring数据JPA的版本。基本上，您不需要findByCustomerId，因为它与findById/findOne相同。我确实在找到了解决方案，但我始终不明白jpa findby为什么不起作用。这是一个非常好的解释是什么在JPA