hibernate关系配置

hibernate中关系的映射有多种，一对一，一对多/多对一，多对多，其中还分单向和双向，其实简单来讲，如果你想获得另一个对象的引用，你就可以在类中定义一个该对象或

该对象的集合。至于表中的关系就是在多方存你的外键而已，如果是多对多，则建立一个中间表，用来存两个关联对象的外键。

一对多&多对一双向

双向关联，在单方设置mapped，将关系由多方主导Group.java

@Entity

@Table(name="t_group")

public class Group {

    private int id;

    private String name;

    private Set<User> users = new HashSet<User>();

    @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;

    }

    @OneToMany(mappedBy="group")

public Set<User> getUsers() {

        return users;

    }

    public void setUsers(Set<User> users) {

        this.users = users;

    }

}

User.java

@Entity

@Table(name="t_user")

public class User {

    private int id;

    private String name;

    private Group group;

    @ManyToOne

    public Group getGroup() {

        return group;

    }

    public void setGroup(Group group) {

        this.group = group;

    }

    @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;

    }

多对多设置中间表"t_s"

Student.java

@Entity

public class Student {

    private int id;

    private String name;

    private Set<Teacher> teachers = new HashSet<Teacher>();

    @ManyToMany(mappedBy="students")

    public Set<Teacher> getTeachers() {

        return teachers;

    }

    public void setTeachers(Set<Teacher> teachers) {

        this.teachers = teachers;

    }

    @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;

    }

}

Teacher.java

@Entity

public class Teacher {

    private int id;

    private String name;

    private Set<Student> students = new HashSet<Student>();

    @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;

    }

    @ManyToMany

    @JoinTable(name="t_s",

        joinColumns={@JoinColumn(name="teacher_id")},

        inverseJoinColumns={@JoinColumn(name="student_id")}

        )

    public Set<Student> getStudents() {

        return students;

    }

    public void setStudents(Set<Student> students) {

        this.students = students;

    }

}