Hibernate -- 映射实体关联关系(一对一关联关系)

一对一关联关系中的两端实体为一一对应

例如：公民与身份证、学生与档案、丈夫与妻子等

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例题：采用外键法映射客户与邮箱之间的单向一对一

客户表为t_users，邮箱表为t_email
选择t_users为主表， t_email为从表

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1.编写实体类 Users
@Entity
@Table(name = “t_users”)
public class Users implements java.io.Serializable {
private Integer usersId;
private String userName;
private Email email;

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "users_id")
public Integer getUsersId() {
    return usersId;
}

public void setUsersId(Integer usersId) {
    this.usersId = usersId;
}

@Column(name = "users_name")
public String getUserName() {
    return userName;
}

public void setUserName(String userName) {
    this.userName = userName;
}

@OneToOne(targetEntity = Email.class, cascade = CascadeType.ALL, fetch = FetchType.LAZY)
@JoinColumn(name = "email_id", insertable = true, unique = true)
public Email getEmail() {
    return email;
}

public void setEmail(Email email) {
    this.email = email;
}

}

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2.编写实体类 Email
@Entity // 在类声明上方加入Entity注解，表示一个实体类，对应数据库的t_email表
@Table(name = “t_email”)
public class Email implements java.io.Serializable {
private Integer emailId;
private String emailName;
private Users users;

public Email() {

}

public Email(String emailName) {
    this.emailName = emailName;
}

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY) // 注解定义主键生成方式，自动增长列
@Column(name = "email_id")
public Integer getEmailId() {
    return emailId;
}

public void setEmailId(Integer emailId) {
    this.emailId = emailId;
}

@Column(name = "email_name")
public String getEmailName() {
    return emailName;
}

public void setEmailName(String emailName) {
    this.emailName = emailName;
}

@OneToOne(mappedBy = "email", fetch = FetchType.EAGER, cascade = CascadeType.ALL)

public Users getUsers() {
    return users;
}

public void setUsers(Users users) {
    this.users = users;
}

}

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3.编写测试文件 DemoOneToOne
public class DemoOneToOne {

public static void main(String[] args) {
    Session s = HibernateSessionFactory.getSession();

    Transaction t = s.beginTransaction();

    Users u = new Users();
    u.setUserName("赵云");

    Email e = new Email("1014867116@qq.com");

    u.setEmail(e);

    s.save(u);

    t.commit();
    s.close();
    System.out.println("操作成功!");
}

}

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4.配置文件