在 RESTful Spring 引导应用程序中，如何对嵌套的 object 属性进行 url 查询？

Question

Here, we are using the following classes, Customer and Address . Assume getters and setters are implemented, and the constructors fill all fields except for the automatically filled id :

@Entity
public class Customer {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private String email;
    @OneToOne
    private Address address;
    /** ... */
}

@Entity
public class Address {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String street;
    private String city;
    private String state;
    private String zipCode;
    /** ... */
}

Notice how the field state is nested inside of the Address instance object inside of the Customer class.

Now our project implements the JpaRepository<Customer, Long> interface in order to handle all queries, and said interface includes a findAll function that takes an Example<Customer> and searches the database according to that example. So we set up our handler

@GetMapping
public ResponseEntity<List<Customer>> getCustomers(@Valid Customer customer) {
    /** call to customerRepository.findAll(Example.of(customer)) inside here */
}

Now in our RESTful application, we type in the URL /customers?state=IL , expecting the customer argument to be fed

new Customer(null, null, new Address(null, null, "IL", null))

but instead, it is fed

new Customer(null, null, null)

Why is that, and what do we have to do to make sure the first object is passed instead of the second?

Answer 1

The easiest way to solve this is to use the @Embedded and @Embeddable annotations.

---

@Entity
public class Customer{
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
private String email;
@Embedded
private Address address;
}


@Entity
@Embeddable 
public class Address{
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String street;
private String city;
private String state;
private String zipCode
}

---

This will solve your problem, @Embedded will embed Address into Customer Entity hence solve your problem.

Answer 2

If you use '@Valid Customer customer' and when you did '/customers?state=IL'no Adress instance will be created automatically.

Because your request wait for a body. Here if you want init a address you should put @param(´state') String state and instanciate manually.