使用 JpaRepository 同时保存一个组合对象

Question

Can I save an object that contains another object directly in the database?

My back-end structure is like this:

1. Rest services
2. Services
3. Repository (extends JpaRepository )
4. Model

Suppose that I have two entity in my model: Company and Address . Both generated by the JPA tool provided by IntelliJ.

Company class model

@Entity
public class Company {
    private int idcompany;
    private String name;
    private Address address;

    @Id
    @Column(name = "idcompany")
    public int getIdcompany() {
        return idcompany;
    }

    public void setIdcompany(int idcompany) {
        this.idcompany = idcompany;
    }

    @Basic
    @Column(name = "name")
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @ManyToOne
    @JoinColumn(name = "idaddress", referencedColumnName = "idaddress", nullable = false)
    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }
}

Address class model

@Entity
public class Address {
    private long idaddress;
    private String zip;

    @Id
    @Column(name = "idaddress")
    public long getIdaddress() {
        return idaddress;
    }

    public void setIdaddress(long idaddress) {
        this.idaddress = idaddress;
    }

    @Basic
    @Column(name = "zip")
    public String getZip() {
        return zip;
    }

    public void setZip(String zip) {
        this.zip = zip;
    }
}

Moreover, both entities have an interface that extends the interface JpaRepository<T,ID> . So, I have CompanyRepository and AddressRepository . I use these two interfaces in they respective Service classes: CompanyService and AddressService . This is where I put the business logic. All ok !

Now, I recive using a REST service, through POST an object Company that contains the object Address . I need to save them into the database (MySql).

In the json file there are Company that contains Address !

Until now, I've always done these steps:

1. Save Address ;
2. Retrieve the Address just saved (i need the idaddress );
3. I associate the Address to the company using setAddress ;
4. Save Company

I tried to save the object Company received via REST calling the method save from CompanyService (using CompanyRepository ) but I got the error:

Column 'idaddress' cannot be null

I ask you. Is there an easier way to save Company and Address at the same time using JpaRepository ???

Answer 1

You don't have defined any cascading.

You could define PERSIST to let the Address persist when Company is persisted:

@ManyToOne
@JoinColumn(name = "idaddress", referencedColumnName = "idaddress", nullable = false,
            cascade = CascadeType.PERSIST)
public Address getAddress() {
    return address;
}

For every method on the EntityManager there is a CascadeType defined.

Read more about the cascade types here: https://vladmihalcea.com/a-beginners-guide-to-jpa-and-hibernate-cascade-types/