JavaPersistenceWithHibernate第二版笔记-第五章-Mapping value types-004嵌套组件的注解AttributeOverrides

一、数据库

二、代码

1.

 package org.jpwh.model.advanced;

 import javax.persistence.AttributeOverride;
 import javax.persistence.AttributeOverrides;
 import javax.persistence.Column;
 import javax.persistence.Embeddable;
 import javax.validation.constraints.NotNull;

 @Embeddable
 public class Address {

     @NotNull
     @Column(nullable = false)
     protected String street;

     @NotNull
     @AttributeOverrides(
         @AttributeOverride(
             name = "name",
             column = @Column(name = "CITY", nullable = false)
         )
     )
     protected City city;

     public String getStreet() {
         return street;
     }

     public void setStreet(String street) {
         this.street = street;
     }

     public City getCity() {
         return city;
     }

     public void setCity(City city) {
         this.city = city;
     }

     // ...
 }

2.

 package org.jpwh.model.advanced;

 import javax.persistence.Column;
 import javax.persistence.Embeddable;
 import javax.validation.constraints.NotNull;

 @Embeddable
 public class City {

     @NotNull
     @Column(nullable = false, length = 5) // Override VARCHAR(255)
     protected String zipcode;

     @NotNull
     @Column(nullable =  false)
     protected String name;

     @NotNull
     @Column(nullable =  false)
     protected String country;

     public String getZipcode() {
         return zipcode;
     }

     public void setZipcode(String zipcode) {
         this.zipcode = zipcode;
     }

     public String getName() {
         return name;
     }

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

     public String getCountry() {
         return country;
     }

     public void setCountry(String country) {
         this.country = country;
     }

     // ...
 }

3.

 package org.jpwh.model.advanced;

 import org.jpwh.model.Constants;

 import javax.persistence.Entity;
 import javax.persistence.GeneratedValue;
 import javax.persistence.Id;
 import javax.persistence.Table;

 @Entity
 @Table(name = "USERS")
 public class User {

     @Id
     @GeneratedValue(generator = Constants.ID_GENERATOR)
     protected Long id;

     public Long getId() {
         return id;
     }

     protected Address address;

     public Address getAddress() {
         return address;
     }

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

You can declare @AttributeOverride s at any level, as you do for the name property of the City class, mapping it to the CITY column. This can be achieved with either (as shown) an @AttributeOverride in Address or an override in the root entity class,User . Nested properties can be referenced with dot notation: for example, on User#address , @AttributeOveride(name = "city.name") references the Address #City#name attribute.