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【学习笔记】Hibernate 注解 （Y2-1-9）

2024-09-04 14:07:11   243人阅读

Hibernate注解

1.什么是注解
在类上或者方法上打上其他类型的类型元数据

 

@标志

使用过的注解:

　　@override 　　方法重写

　　@Test　　　　 Junit 单元测试

　　@Before　　　单元测试

　　@After　　　　单元测试

 

Hibernate中常用的注解

 

1.@Entity 将一个类声明为持久化类
2.@ID 声明持久化类的标识属性
3.@GeneratedValue 定义标识属性值的生成策略,默认为native
4.@Column 将属性映射到类
5.@Table 持久化类映射指定表
6.@Transient 忽略这些属性

 

Hibernate中可以使用小配置文件来关联映射,也可以使用注解.

 

1.一对一关联

一个人Human 有一个身份证号Identity 一个身份证号只属于一个人

实体类如下

@Entity
@Table
public class Human {
    private Integer hid;
    @Column
    private String hname;
    private Identity identity;

    @OneToOne
    @JoinColumn(name = "iid")
    public Identity getIdentity() {
        return identity;
    }

    public void setIdentity(Identity identity) {
        this.identity = identity;
    }

    @Id
    @GeneratedValue
    public Integer getHid() {
        return hid;
    }

    public void setHid(Integer hid) {
        this.hid = hid;
    }

    public String getHname() {
        return hname;
    }

    public void setHname(String hname) {
        this.hname = hname;
    }
}
@Entity
@Table
public class Identity {
    private Integer iid;
    private String inum;
    private Human human;

    @OneToOne(mappedBy = "identity", cascade = CascadeType.ALL)
    public Human getHuman() {
        return human;
    }

    public void setHuman(Human human) {
        this.human = human;
    }

    @Id
    @GeneratedValue
    public Integer getIid() {
        return iid;
    }

    public void setIid(Integer iid) {
        this.iid = iid;
    }

    public String getInum() {
        return inum;
    }

    public void setInum(String inum) {
        this.inum = inum;
    }
}

测试如下

@Test
    public void insert() {
        Identity id = new Identity();
        id.setInum("1231231212123");

        Human human = new Human();
        human.setHname("鬼");
        human.setIdentity(id);

        id.setHuman(human);
        session.save(human);
        session.save(id);
    }

 

 

2.双向一对多关联

一个部门Dept 有多个员工Emp 一个员工只能属于一个部门

实体类如下

@Entity
@Table(name = "dept3")
public class Dept {
    @Id
    @GeneratedValue
    private Integer deptid;
    private String dname;
    @OneToMany(mappedBy = "dept", cascade = {CascadeType.ALL})
    private Set<Emp> emps = new HashSet<Emp>();

    public Integer getDeptid() {
        return deptid;
    }

    public void setDeptid(Integer deptid) {
        this.deptid = deptid;
    }

    public String getDname() {
        return dname;
    }

    public void setDname(String dname) {
        this.dname = dname;
    }

    public Set<Emp> getEmps() {
        return emps;
    }

    public void setEmps(Set<Emp> emps) {
        this.emps = emps;
    }
}
@Entity
@Table(name = "Emp3")
public class Emp {
    @Id
    @GeneratedValue
    private Integer eid;
    private String ename;
    @ManyToOne
    @JoinColumn(name = "deptid")
    private Dept dept;

    public Integer getEid() {
        return eid;
    }

    public void setEid(Integer eid) {
        this.eid = eid;
    }

    public String getEname() {
        return ename;
    }

    public void setEname(String ename) {
        this.ename = ename;
    }

    public Dept getDept() {
        return dept;
    }

    public void setDept(Dept dept) {
        this.dept = dept;
    }
}

测试如下

@Test
    public void insert() {
        Dept dept = new Dept();
        dept.setDname("鬼畜部");

        Emp emp1 = new Emp();
        emp1.setEname("天命");
        emp1.setDept(dept);

        Emp emp2 = new Emp();
        emp2.setEname("斯沃");
        emp2.setDept(dept);

        Set<Emp> set = new HashSet<Emp>();
        set.add(emp1);
        set.add(emp2);
        dept.setEmps(set);

        session.save(dept);
    }

 

 

3.多对多关联

一个玩家Player 可以玩多个游戏Game 一个游戏可以被多个玩家玩

实体类如下

@Entity
@Table
public class Game {
    @Id
    @GeneratedValue
    private Integer gid;
    private String gname;
    @ManyToMany(cascade = CascadeType.ALL)
    @JoinTable(name = "",
            joinColumns = {@JoinColumn(name = "gid")},
            inverseJoinColumns = {@JoinColumn(name = "pid")})
    private Set<Player> players = new HashSet<Player>();

    public Integer getGid() {
        return gid;
    }

    public void setGid(Integer gid) {
        this.gid = gid;
    }

    public String getGname() {
        return gname;
    }

    public void setGname(String gname) {
        this.gname = gname;
    }

    public Set<Player> getPlayers() {
        return players;
    }

    public void setPlayers(Set<Player> players) {
        this.players = players;
    }
}
@Entity
@Table
public class Player {
    @Id
    @GeneratedValue
    private Integer pid;
    private String pname;
    @ManyToMany(cascade = CascadeType.ALL, mappedBy = "players")
    private Set<Game> games = new HashSet<Game>();

    public Integer getPid() {
        return pid;
    }

    public void setPid(Integer pid) {
        this.pid = pid;
    }

    public String getPname() {
        return pname;
    }

    public void setPname(String pname) {
        this.pname = pname;
    }

    public Set<Game> getGames() {
        return games;
    }

    public void setGames(Set<Game> games) {
        this.games = games;
    }
}

测试如下

@Test
    public void insert(){
        Game g1=new Game();
        g1.setGname("我的课堂");
        Game g2=new Game();
        g2.setGname("感恩的心");

        Player p1=new Player();
        p1.setPname("Chara");
        Player p2=new Player();
        p2.setPname("Frisk");

        g1.getPlayers().add(p1);
        g1.getPlayers().add(p2);
        g2.getPlayers().add(p1);
        g2.getPlayers().add(p2);

        session.save(g1);
        session.save(g2);
    }

 

【学习笔记】Hibernate 注解 （Y2-1-9）


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