Question

hibernate多对多映射文件配置位置

当两个实体是多对多联系时，联系集有一个多int型字段，如何在hibernate中设置。
比如：
create table student
(
id int primary key,
name varchar(10),
)

create table course
(
id int primary key,
name varchar(10),
)

create table student_course
(
studentId int references student(id),
courseId int references course(id),
score int, ------成绩
primary key (studentId, courseId),
)

Answer 1

不要用多对多

把多对多 拆开 拆成两个一对多，中间表一定要有自己的主键

然后另外两张一表的主键作为中间表的外键

建立两次关联

注意 我曾经给Gavin King 发过email， hibernate永远不要用复合主键
也就是composite-id

Answer 2

采用JPA标注实体类挺简单的
import java.util.HashSet;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.ManyToMany;
import javax.persistence.Table;

@Entity
@Table(name="student")
public class Student {
private int id;
private String name;
private Set<Course> courses=new HashSet<Course>();

@Id
@GeneratedValue
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@Column(name="sname")
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@ManyToMany(cascade={CascadeType.ALL})
@JoinTable(name="student_course",
joinColumns={@JoinColumn(name="student_id")},
inverseJoinColumns={@JoinColumn(name="course_id")}
)
public Set<Course> getCourses() {
return courses;
}
public void setCourses(Set<Course> courses) {
this.courses = courses;
}
}

Course 类：
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="course")
public class Course {
private int id;
private String name;

@Id
@GeneratedValue
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@Column(name="cname")
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

@Entity
@Table(name="student_course")
public class Score {
private int score;
private Student student;
private Course course;

public int getScore() {
return score;
}
public void setScore(int score) {
this.score = score;
}

@ManyToOne(cascade={CascadeType.ALL})
@JoinColumn(name="student_id")
public Student getStudent() {
return student;
}
public void setStudent(Student student) {
this.student = student;
}
@ManyToOne(cascade={CascadeType.ALL})
@JoinColumn(name="course_id")
public Course getCourse() {
return course;
}
public void setCourse(Course course) {
this.course = course;
}
}
如果想采用XML配置的话，请参考Hiberante的官方文档，里面有详细的配置

Answer 3

你想表达什么意思？ 多多多关联 用 3张表 中间表用联合主键就行
映射文件是对 实体的映射 用 Many-To-Many