JPAのOneToOne関係処理

関係データベースを早く勉強したとき、一対多、多対一、一対一、多対多の関係を学んだことがあります.前に1対多と多対一の関係を紹介しました.1対1を見てみましょう.
[color=red]ビジネス要件:一般的には、1人につき1つの身分証明書番号しかありません(特殊な場合を除きます).[/color]
次に、人と身分証明書エンティティクラスを示します.

 import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;

@Entity
public class Person {
	private Integer id;
	private String name;
	private IDCard idcard;

	public Person(){}

	public Person(String name){
		this.name = name;
	}

	@Id @GeneratedValue
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	@Column(length=10,nullable=false)
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	@OneToOne(optional=false,cascade={CascadeType.ALL})
	@JoinColumn(name="idcard_id")
	public IDCard getIdcard() {
		return idcard;
	}
	public void setIdcard(IDCard idcard) {
		this.idcard = idcard;
	}
}

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;

@Entity
public class IDCard {
	private Integer id;
	private String cardno;
	private Person person;

	public IDCard(){}

	public IDCard(String cardno) {
		this.cardno = cardno;
	}
this.person = person;
	}
	@Id @GeneratedValue
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	@Column(length=18,nullable=false)
	public String getCardno() {
		return cardno;
	}
	public void setCardno(String cardno) {
		this.cardno = cardno;
	}

	@OneToOne(mappedBy="idcard",cascade={CascadeType.REFRESH,CascadeType.MERGE,CascadeType.REFRESH})
	public Person getPerson() {
		return person;
	}
	public void setPerson(Person person) {

}

テストクラス

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import org.junit.BeforeClass;
import org.junit.Test;

import cn.itcast.bean.IDCard;
import cn.itcast.bean.Person;

public class OneToOneTest {

	@BeforeClass
	public static void setUpBeforeClass() throws Exception {
	}
	@Test public void add(){
		 EntityManagerFactory factory = Persistence.createEntityManagerFactory("test");
		 EntityManager em = factory.createEntityManager();
		 em.getTransaction().begin(); // start transaction
		 Person person = new Person("   ");
		 person.setIdcard(new IDCard("88888888888"));
		 em.persist(person);
		 em.getTransaction().commit(); //commit transaction
		 em.close();
		 factory.close();
	}
}

[b]まとめ:1対1は[url=http://jiangduxi.iteye.com/blog/646693[1]多[/url]を考慮し,その関係維持端は作成者自身が定義する.
[/b]