hibernate關係配置

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hibernate中關係的映射有多種，一對一，一對多/多對一，多對多，其中還分單向和雙向，其實簡單來講，如果你想獲得另一個對象的引用，你就可以在類中定義一個該對象或

該對象的集合。至於表中的關係就是在多方存你的外鍵而已，如果是多對多，則建立一個中間表，用來存兩個關聯對象的外鍵。

一對多&多對一雙向

雙向關聯，在單方設定mapped，將關係由多方主導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;    }

多對多設定中間表"t_s"

Student.java

@Entitypublic 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

@Entitypublic 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;    }}