Question

我的表客户有参数：

@Entity
public class Customer {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    public Long id;
    public Long id_crm;
    public String City;
    public String Country;

和第二个表格，我存储了一些联系信息。

@Entity
public class CustomerContact {
  @Id
  public Long id;
  public Role role;
  public Department department;
  public Long customer_id_crm
}

第二个表是从外部crm app获得的，因此我已将关系列id_crm添加为外键。

我想在列上的这两个实体之间建立关系： Customer.id_crm和CustomerContact.customer_id_crm

对它的sql查询将如下所示：

Select * FROM Customer 
Join CustomerContact 
on Customer.id_crm=CustomerContact.customer_id_crm

我甚至可以用jpa实现这个目标吗？如果是这样？怎么做？

Answer 1

试试这个

session.createQuery("select c, cc from Customer c, CustomerContact cc where c.id_crm = cc.customer_id_crm")

Answer 2

这是与canvas有一对多关系的person类：

@Entity
@Table(name="person")
public class Person implements UserDetails{


    @Id
    @Column(name="id")
    @GeneratedValue(strategy = GenerationType.SEQUENCE,generator = "person_seq_gen")
    @SequenceGenerator(name = "person_seq_gen",sequenceName = "person_seq")
    private int id;
@OneToMany(mappedBy = "person1",fetch = FetchType.EAGER,cascade = CascadeType.REMOVE)
    private Set<Canvas> canvas1 = new HashSet<Canvas>();

    public Set<Canvas> getCanvas1() {
        return canvas1;
    }

    public void setCanvas1(Set<Canvas> canvas1) {

        this.canvas1 = canvas1;
    }
}

画布模型：

@Entity
@Table(name = "canvas")
public class Canvas {

    @Id
    @Column(name="canvasid")
    @GeneratedValue(strategy = GenerationType.SEQUENCE,generator = "canvas_gen")
    @SequenceGenerator(name = "canvas_gen",sequenceName = "canvas_seq")
    private int canvasid;

 @ManyToOne
    @JoinColumn(name = "id",nullable = false)
    @JsonIgnore 
    private Person person1;

    public Person getPerson1() {
        return person1;
    }

    public void setPerson1(Person person1) {
        this.person1 = person1;
    }

    public int getPerson1id(){
        return this.person1.getId();
    }
}

当你想要添加画布时，这是DAOImpl：

public void addCanvas(Canvas canvas, Person person) {
        int id = person.getId();
        if( session == null) {
            session = this.sessionFactory.openSession();
        }else {
            session = this.sessionFactory.getCurrentSession();
        }
        Person person1 = (Person) session.get(Person.class,id);
        person.getCanvas1().add(canvas);
        canvas.setPerson1(person1);
        session.merge(canvas);
        session.flush();

    }

我也有类似于你的查询的方法：

public List<Canvas> listCanvasPerson(Person person) {
       int id = person.getId();
        if(session == null){
            session = this.sessionFactory.openSession();
        } else{
            session = this.sessionFactory.getCurrentSession();
        }

        Query query = session.createQuery("from Canvas as c where c.person1.id=:id order by c.canvasnumber");
        query.setParameter("id",id);
        List<Canvas> canvasList = query.list();

希望这会有所帮助，如果我在某个地方犯了错误，请告诉我。请理解我使用的是简单的密钥，而不是复合密钥。

jpa OneToMany关于专用参数/列的关系

2 个答案: