这里我们仍然是使用annotation对实体进行配置。使用person与idcard模拟一对一的关联关系，一个人只能有一个ID号，同样一个ID号只能对应一个人，人与ID号是一对一的关联关系。Person类如下：
1 package com.yichun.bean; 2 3 import javax.persistence.CascadeType; 4 import javax.persistence.Column; 5 import javax.persistence.Entity; 6 import javax.persistence.GeneratedValue; 7 import javax.persistence.Id; 8 import javax.persistence.JoinColumn; 9 import javax.persistence.OneToOne; 10 import javax.persistence.Table; 11 12 //关系的维护端 13 @Entity 14 @Table(name = "person") 15 public class Person { 16 private Integer id; 17 private String name; 18 private IDCard idcard; 19 20 public Person() { 21 } 22 23 public Person(String name) { 24 this.name = name; 25 } 26 27 @Id 28 @GeneratedValue 29 public Integer getId() { 30 return id; 31 } 32 33 public void setId(Integer id) { 34 this.id = id; 35 } 36 37 @Column(length = 10, nullable = false) 38 public String getName() { 39 return name; 40 } 41 42 public void setName(String name) { 43 this.name = name; 44 } 45 46 @OneToOne(optional = false, cascade = CascadeType.ALL)//级联保存、修改、删除、同步 47 @JoinColumn(name = "idcard_id")// 外键的名称idcard_id 48 public IDCard getIdcard() { 49 return idcard;50 } 51 52 public void setIdcard(IDCard idcard) {53 this.idcard = idcard; 54 } 55 }
IDCard类如下：
1 package com.yichun.bean; 2 3 import javax.persistence.CascadeType; 4 import javax.persistence.Column; 5 import javax.persistence.Entity; 6 import javax.persistence.GeneratedValue; 7 import javax.persistence.Id; 8 import javax.persistence.OneToOne; 9 import javax.persistence.Table; 10 11 //关系被维护端 12 @Entity 13 @Table(name = "idcard") 14 public class IDCard { 15 private Integer id; 16 private String cardno; 17 private Person person; 18 19 public IDCard() { 20 } 21 22 public IDCard(String cardno) { 23 this.cardno = cardno; 24 } 25 26 @Id 27 @GeneratedValue 28 public Integer getId() { 29 return id; 30 } 31 32 public void setId(Integer id) { 33 this.id = id; 34 } 35 36 @Column(length = 18, nullable = false) 37 public String getCardno() { 38 return cardno; 39 } 40 41 public void setCardno(String cardno) { 42 this.cardno = cardno; 43 } 44 45 // 出现mappedBy的就是关系被维护端,由idCard维护, optional = false可以不设置 46 @OneToOne(mappedBy = "idcard", cascade = { CascadeType.PERSIST, 47 CascadeType.MERGE, CascadeType.REFRESH })//CascadeType.PERSIST 级联保存,CascadeType.MERGE 级联更新,CascadeType.REFRESH 级联刷新 48 public Person getPerson() { 49 return person; 50 } 51 52 public void setPerson(Person person) { 53 this.person = person; 54 } 55 }
保存数据
1 @Test 2 public void save() { 3 EntityManagerFactory factory = Persistence 4 .createEntityManagerFactory("testjpa"); 5 EntityManager manager = factory.createEntityManager(); 6 manager.getTransaction().begin(); 7 8 Person person = new Person("张三"); 9 IDCard idCard = new IDCard("1111122222"); 10 person.setIdcard(idCard); 11 // 1、保存person 12 // 2、保存IDCard 13 // 3、使用IDCard的id作为外键保存到person里面 14 manager.persist(person); 15 16 manager.getTransaction().commit(); 17 manager.close(); 18 factory.close(); 19 }
