07-hibernate注解-一对多（多对一）双向外键关联

一对多（多对一）双向外键

多方：多方持有一方的引用。

@ManyToOne(cascade={CasCadeType.ALL},fetch=FetchType.EAGER)

@JoinColumn(name="cid")

一方：一方持有多方的集合。

@OneToMany(@cascade={CascadeType.ALL},fetch=FetchType.LAZY)

@JoinColumn(name="cid")

第一步：建立学生表：

1，对应学生类：因为多方持有一方，添加注解：@ManyToOne。

package otm_bfk；
import java.util.Date;
import javax.persistence.CascadeType;
import javax.persistence.Entity;/*JPA主键*/
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

import org.hibernate.annotations.CacheModeType;

/*学生实体类*/
@Entity
@Table(name="Students",schema="sys")
public class Students {

    private int sid;
    private String name;
    private String gender;//性别
    private Date birthday;
    private String major;//专业

    private ClassRoom classRoom;//多方持有一方的引用

    public Students()
    {

    }

    public Students( String name,String gender, Date birthday, String major) {
        //super();
        this.name=name;
        this.gender = gender;
        this.birthday = birthday;
        this.major = major;
    }

    @Id
    @GeneratedValue //主键自动增长
    public int getSid() {
        return sid;
    }
    public void setSid(int sid) {
        this.sid = sid;
    }

    @ManyToOne(cascade={CascadeType.ALL},fetch=FetchType.EAGER)
    @JoinColumn(name="cid")
    public ClassRoom getClassRoom() {
        return classRoom;
    }
    public void setClassRoom(ClassRoom classRoom) {
        this.classRoom = classRoom;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public String getName() {
        return name;
    }

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

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getMajor() {
        return major;
    }

    public void setMajor(String major) {
        this.major = major;
    }
}

第二部：班级类和测试类代码跟前面的一对多单向一样。

测试结果：