hibernate基于注解实现映射关系的配置

关联关系的配置步骤

①要理清楚管理关系
②确定管理依赖关系的哪一方

1一对一
例如：person 和IdCard

　　①确定依赖关系：一对一

　　②依赖关系由person类管理
代码如下：

person:

@Entity
@Table(name="t_person")
public class Person
{
    private int id;
    private String name;
    private IDCard card;
    
    @OneToOne(mappedBy="person")　　--->　　指定了OneToOne的关联关系，
　　 @joinColmun(name="idcard")
    public IDCard getCard()
    {
        return card;
    }
    public void setCard(IDCard card)
    {
        this.card = card;
    }
    @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;
    }
    
}

IDCard:

@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(mappedBy="idCard")--->　　OnetoOne指定了一对一的关联关系，一对一中随便指定一方来维护映射关系，mappedBy同样指定由对方来进行维护关联关系,这里选择Person来进行维护   public Person getPerson() { 
      return person; 
   }
  publicvoid setPerson(Person person) {
   this.person = person; 
  } 
}

2一对多

例如：teacher和student

　　①确定依赖关系：一对多

　　②依赖关系由多方（student）管理

代码：

 teacher:

public class Teacher {

    
    private String name;
    private  Set<Student> student=new HashSet<Student>();
    
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    @OneToMany(mappedBy="teacher",fetch=FetchType.LAZY)
    public Set<Student> getStudent() {
        return student;
    }
    public void setStudent(Set<Student> student) {
        this.student = student;
    }
    
}

student:

public class Student{
    private String name;
    private  Teacher teacher;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name="teacher")
    public Teacher getTeacher() {
        return teacher;
    }
    public void setTeacher(Teacher teacher) {
        this.teacher = teacher;
    }
    
}

3多对多

例如：classRoom和student

　　①确定依赖关系：多对多

　　②依赖关系由多方（student）管理

classRoom:

public class ClassRoom{

    private String name;
    private Set<Student> students=new HashSet<Student>();
    
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    @ManyToMany(mappedBy="calssRooms",fetch=FetchType.LAZY)
    public Set<Student> getStudents() {
        return students;
    }
    public void setStudents(Set<Student> students) {
        this.students = students;
    }
    
    
}

student:

public class Student{
    private String name;
    private  Set<ClassRoom> classRooms=new HashSet<ClassRoom>();
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    @ManyToMany(fetch=FetchType.LAZY)
    @JoinTable(name="xx_classRoom_student")
    public Set<ClassRoom> getClassRooms() {
        return classRooms;
    }
    public void setClassRooms(Set<ClassRoom> classRooms) {
        this.classRooms = classRooms;
    }
    
}