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：