Hibernate-Annotation（下）-阿里云开发者社区

Hibernate-Annotation（下）

2022-06-08 123

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简介： Hibernate-Annotation（下）

三，关系映射级别注解

1. 一对一单向外键关联(两张表都要在hibernate住配置文件中进行配置)

//主表
package Entity;
import javax.persistence.*;
import java.sql.Timestamp;
/**
 * Created by futao on 2017/9/27.
 */
@Entity
@Table(name = "imooc_student")
public class Student {
    /**
     * 主键，学号
     */
    @Id
    @GeneratedValue
    private int sid;
    /**
     * 性别
     */
    private String gender;
    /**
     * 生日
     */
    private Timestamp birthday;
    /**
     * 专业
     */
    private String major;
    /**
     * 身份证对象
     */
    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "pid",unique = true)
    private IdCard idCard;
    public IdCard getIdCard() {
        return idCard;
    }
    public void setIdCard(IdCard idCard) {
        this.idCard = idCard;
    }
    public int getSid() {
        return sid;
    }
    public void setSid(int sid) {
        this.sid = sid;
    }
    public String getGender() {
        return gender;
    }
    public void setGender(String gender) {
        this.gender = gender;
    }
    public Timestamp getBirthday() {
        return birthday;
    }
    public void setBirthday(Timestamp birthday) {
        this.birthday = birthday;
    }
    public String getMajor() {
        return major;
    }
    public void setMajor(String major) {
        this.major = major;
    }
}

//关联表
package Entity;
import org.hibernate.annotations.GenericGenerator;
import javax.persistence.*;
/**
 * Created by futao on 2017/9/27.
 */
@Entity
@Table(name = "imoooc_id_card")
public class IdCard {
    @Id
    @GeneratedValue(generator = "pid")
    @GenericGenerator(name="pid",strategy = "assigned")
    @Column(length = 18)
    private String pid;
    private String sname;
    private String address;
    public String getPid() {
        return pid;
    }
    public void setPid(String pid) {
        this.pid = pid;
    }
    public String getSname() {
        return sname;
    }
    public void setSname(String sname) {
        this.sname = sname;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
}

//Test
    @Test
    fun dbtest() {
        session.save(IdCard().apply {
            pid = "11"
            sname = "熊anger"
            address = "上海小二房"
        })
        session.save(Student().apply {
            gender = "男"
            birthday = Timestamp(DateTime.now().millis)
            major = "计算机"
            idCard = session.get(Student::class.java, 2) as IdCard
        })
    }

2. 不推荐使用双向外键关联

3. 多对一单向外键关联

//多的那一方
package ManyToOne;
import javax.persistence.*;
import java.sql.Timestamp;
/**
 * Created by futao on 2017/9/28.
 */
/**
 * 学生实体类
 */
@Entity
@Table(name = "imooc_senior_student")
public class Student {
    @Id
    @GeneratedValue
    private int sid;
    private String gender;
    private Timestamp birthday;
    private String major;
    /**
     * 一对多单向外键关联关系
     * 级联关系：全级连
     * 抓取策略
     */
//@joinColumn(name="对用生成的表中的字段名",referencedColumnName="一的那一方的主键名")
    @ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    @JoinColumn(name = "fuckyou",referencedColumnName ="cid" )
    private Classroom classroom;
    public Classroom getClassroom() {
        return classroom;
    }
    public void setClassroom(Classroom classroom) {
        this.classroom = classroom;
    }
    public int getSid() {
        return sid;
    }
    public void setSid(int sid) {
        this.sid = sid;
    }
    public String getGender() {
        return gender;
    }
    public void setGender(String gender) {
        this.gender = gender;
    }
    public Timestamp getBirthday() {
        return birthday;
    }
    public void setBirthday(Timestamp birthday) {
        this.birthday = birthday;
    }
    public String getMajor() {
        return major;
    }
    public void setMajor(String major) {
        this.major = major;
    }
}

//一的那一方
package ManyToOne;
import org.hibernate.annotations.GenericGenerator;
import javax.persistence.*;
/**
 * Created by futao on 2017/9/28.
 */
/**
 * 班级实体类
 */
@Entity
@Table(name = "imooc_senior_classroom")
public class Classroom {
    @Id
    @GeneratedValue(generator = "cid")
    @GenericGenerator(name = "cid",strategy = "assigned")
    @Column(length = 4)
    private String cid;
    private String cname;
    public String getCid() {
        return cid;
    }
    public void setCid(String cid) {
        this.cid = cid;
    }
    public String getCname() {
        return cname;
    }
    public void setCname(String cname) {
        this.cname = cname;
    }
}

4. 多对多单向外键

多对多会生成一张中间表存储对应关系

package Many2Many;
import javax.persistence.*;
import java.sql.Timestamp;
import java.util.Set;
/**
 * Created by futao on 2017/9/28.
 */
@Entity
@Table(name = "many2many_student")
public class Student {
    @Id
    @GeneratedValue
    private int sid;
    private String name;
    private String gender;
    private Timestamp birthday;
    private String major;
    /**
     * 学生持有教师的集合
     */
    @ManyToMany
    @JoinTable(
            //中间表的名字
            name = "student_teacher",
            joinColumns = {@JoinColumn(name = "sid")},
            inverseJoinColumns = {@JoinColumn(name = "tid")}
    )
    private Set<Teacher> teacherSet;
    public Set<Teacher> getTeacherSet() {
        return teacherSet;
    }
    public void setTeacherSet(Set<Teacher> teacherSet) {
        this.teacherSet = teacherSet;
    }
    public int getSid() {
        return sid;
    }
    public void setSid(int sid) {
        this.sid = sid;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getGender() {
        return gender;
    }
    public void setGender(String gender) {
        this.gender = gender;
    }
    public Timestamp getBirthday() {
        return birthday;
    }
    public void setBirthday(Timestamp birthday) {
        this.birthday = birthday;
    }
    public String getMajor() {
        return major;
    }
    public void setMajor(String major) {
        this.major = major;
    }
}

package Many2Many;
import org.hibernate.annotations.GenericGenerator;
import javax.persistence.*;
/**
 * Created by futao on 2017/9/28.
 */
@Entity
@Table(name = "many2many_teacher")
public class Teacher {
    @Id
    @GeneratedValue(generator = "tid")
    @GenericGenerator(name = "tid", strategy = "assigned")
    @Column(length = 4)
    private String tid;
    private String tname;
    public String getTid() {
        return tid;
    }
    public void setTid(String tid) {
        this.tid = tid;
    }
    public String getTname() {
        return tname;
    }
    public void setTname(String tname) {
        this.tname = tname;
    }
}

@Test
    fun many2many(){
        val t1=Teacher().apply {
            tid="T001"
            tname="张老师"
        }
        val t2=Teacher().apply {
            tid="t999"
            tname="吴彦祖"
        }
        val teachers=HashSet<Teacher>()
        teachers.add(t1)
        teachers.add(t2)
        val s1=Many2Many.Student().apply {
            name="熊老一"
            gender="男"
            birthday= Timestamp(DateTime.now().millis)
            major="计算机"
            teacherSet=teachers
        }
        val s2= Many2Many.Student().apply {
            name="熊老二"
            gender="男"
            birthday= Timestamp(DateTime.now().millis)
            major="软件工程"
        }
        val s3=Many2Many.Student().apply {
            name="李子"
            gender="女"
            birthday= Timestamp(DateTime.now().millis)
            major="建筑学"
            teacherSet=teachers
        }
        session.save(t1)
        session.save(t2)
        session.save(s1)
        session.save(s2)
        session.save(s3)
    }