3、Hibernate的Annotation

特别注意：Hibernate的Annotation要依赖于JPA包。

在Hibernate的3.5之前都需要下载Hibernate的Annotation的jar包，在3.5之后Hibernate的Annotation jar包已

3.1、基本映射

//注意是javax.persistence.Entity@Entity//设置表名@Table(name="t_user")public class User {	private int id;	private String username;	private String password;	private String nickname;	private Date born;	private Date createDate;		//@Column可以为这个字段进行定义	@Column(name="create_date")	public Date getCreateDate() {		return createDate;	}	public void setCreateDate(Date createDate) {		this.createDate = createDate;	}		//标志为id属性	@Id	//GeneratedValue表示自动递增	@GeneratedValue	public int getId() {		return id;	}	public void setId(int id) {		this.id = id;	}

3.2、一对一

@Entity@Table(name="t_id_card")public class IDCard {	private int id;	private String no;	private Person person;		@Id	@GeneratedValue	public int getId() {		return id;	}	public void setId(int id) {		this.id = id;	}	public String getNo() {		return no;	}	public void setNo(String no) {		this.no = no;	}		@OneToOne	//@JoinColumn可以设置外键的名称。	//只要使用了OneToOne就会在自己的表中增加外键。	@JoinColumn(name="pid")	public Person getPerson() {		return person;	}	public void setPerson(Person person) {		this.person = person;	}

@Entity@Table(name="t_person")public class Person {	private int id;	private String name;	private IDCard idCard;		//只要设置了@OneToOne就会在自己的表中增加外键，所以只有设置mappedBy="自己在对端的属性名称"	//才能说明关系由对方维护	@OneToOne(mappedBy="person") //对端的属性名称，说明关系由对方来维护	public IDCard getIdCard() {		return idCard;	}	public void setIdCard(IDCard idCard) {		this.idCard = idCard;	}		@Id	@GeneratedValue	public int getId() {		return id;	}	public void setId(int id) {		this.id = id;	}	public String getName() {		return name;	}	public void setName(String name) {		this.name = name;	}

3.3、一对多

m：1单向：

@ManyToOne(fetch=FetchType.LAZY) //延迟加载	//外键名称	@JoinColumn(name="cid")	public Classroom getClassroom() {		return classroom;	}	public void setClassroom(Classroom classroom) {		this.classroom = classroom;	}

1：m单向：

@OneToMany    //加入到对方表中的外键    @JoinColumn(name="cid")    //等于xml中的lazy="extra"	@LazyCollection(LazyCollectionOption.EXTRA)	public Set
    
      getStudents() {		return students;	}	public void setStudents(Set
     
       students) {		this.students = students;	}
     
    

双向：

@ManyToOne(fetch=FetchType.LAZY) //延迟加载	//外键名称	@JoinColumn(name="cid")	public Classroom getClassroom() {		return classroom;	}	public void setClassroom(Classroom classroom) {		this.classroom = classroom;	}    @OneToMany(mappedBy="classroom")    //@JoinColumn(name="cid")    //设置了mappedBy就已经等于说明由对方维护关系，所以不同在设置JoinColumn	@LazyCollection(LazyCollectionOption.EXTRA)	public Set
    
      getStudents() {		return students;	}	public void setStudents(Set
     
       students) {		this.students = students;	}
     
    

3.4、多对多

多对多双向：

@ManyToMany	//name="t_role_admin"表示关联表的名称，	//joinColumns={@JoinColumn(name="rid")}表示自己在关联表中的外键名称，是数组	//inverseJoinColumns={@JoinColumn(name="aid")}表示对方在关联表中的外键名称，也是数组	@JoinTable(name="t_role_admin",joinColumns={@JoinColumn(name="rid")},				inverseJoinColumns={@JoinColumn(name="aid")})	public Set
    
      getAdmins() {		return admins;	}	public void setAdmins(Set
     
       admins) {		this.admins = admins;	}    @ManyToMany(mappedBy="admins") //由对方维护关系	public Set
      
        getRoles() {		return roles;	}	public void setRoles(Set
       
         roles) {		this.roles = roles;	}
       
      
     
    

两个一对多：

@OneToMany(mappedBy="course")	@LazyCollection(LazyCollectionOption.EXTRA)	public Set
    
      getTcs() {		return tcs;	}	public void setTcs(Set
     
       tcs) {		this.tcs = tcs;	}    @OneToMany(mappedBy="teacher")	@LazyCollection(LazyCollectionOption.EXTRA)	public Set
      
        getTcs() {		return tcs;	}	public void setTcs(Set
       
         tcs) {		this.tcs = tcs;	}    @ManyToOne	@JoinColumn(name="tid")	public Teacher getTeacher() {		return teacher;	}	public void setTeacher(Teacher teacher) {		this.teacher = teacher;	}		@ManyToOne	@JoinColumn(name="cid")	public Course getCourse() {		return course;	}	public void setCourse(Course course) {		this.course = course;	}