hibernate关联映射(注解) —— 基于主键的双向一对一关联映射(@OneToOne)

hibernate基于注解的一对多关联使用@OneToOne注解。
注意：需要引入的为： javax.persistence.OneToOne

---

维护端(有外键方)：

@Id
@GenericGenerator(name = "pkGenerator", strategy = "foreign", 
    parameters = { @Parameter(name = "property", value = "idCard") })  
@GeneratedValue(generator = "pkGenerator")
@Column(name = "userId")
public int getUserId() {
    return userId;
}

@OneToOne
@PrimaryKeyJoinColumn
@Cascade(CascadeType.ALL) // 设置级联操作
public IdCard getIdCard() {
    return idCard;
}

被维护端(无外键方)：

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "idCardId")
public int getId() {
    return Id;
}

@OneToOne(mappedBy = "idCard")
@Cascade(CascadeType.ALL)
@PrimaryKeyJoinColumn
public User getUser() {
    return user;
}

---

假设有两个类：User(用户)与IdCard(身份证)，一个用户对应一个身份证。

User 类 如下

import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.Table;

import org.hibernate.annotations.Cascade;
import org.hibernate.annotations.CascadeType;
import org.hibernate.annotations.GenericGenerator;
import org.hibernate.annotations.Parameter;

@Entity
@Table(name = "user")
public class User {
    private int userId;
    private String username;
    private IdCard idCard;

    @Id
    @GenericGenerator(name = "pkGenerator", strategy = "foreign", 
        parameters = { @Parameter(name = "property", value = "idCard") })  
    @GeneratedValue(generator = "pkGenerator")
    @Column(name = "userId")
    public int getUserId() {
        return userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    @Basic
    @Column(name = "username")
    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    @OneToOne
    @PrimaryKeyJoinColumn
    @Cascade(CascadeType.ALL) // 设置级联操作
    public IdCard getIdCard() {
        return idCard;
    }

    public void setIdCard(IdCard idCard) {
        this.idCard = idCard;
    }

}

IdCard 类 如下

import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.Table;

import org.hibernate.annotations.Cascade;
import org.hibernate.annotations.CascadeType;

@Entity
@Table(name = "idCard")
public class IdCard {
    private int Id;
    private String idno;
    private User user;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "idCardId")
    public int getId() {
        return Id;
    }

    public void setId(int id) {
        Id = id;
    }

    @Basic
    @Column(name = "idno", nullable = false)
    public String getIdno() {
        return idno;
    }

    public void setIdno(String idno) {
        this.idno = idno;
    }

    @OneToOne(mappedBy = "idCard")
    @Cascade(CascadeType.ALL)
    @PrimaryKeyJoinColumn
    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }

}