Hibernate多对多中间表有多个字段字段的注解配置方式（三）

来源：互联网发布：姜文王朔知乎编辑：程序博客网时间：2024/05/22 00:27

情况三：本示例主要以学生（T_Student）和课程（T_Course）之间的多对多关系，中间表Score（分数），学生表和课程表是多对多关系，另外为他们的关系添加额外的字段---分数：

T_Student类如下：

package server.com.upc.test;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

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.MapKey;

@Entity
public class T_Student {
private int  id;
private String name;
private Map<String,T_Crouse>  course=new HashMap<String,T_Crouse>();

@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
@MapKey(name="id")
@JoinTable(
   name="score",
   joinColumns=@JoinColumn(name="student_id"),
   inverseJoinColumns=@JoinColumn(name="course_id")
   )
public Map<String, T_Crouse> getCourse() {
  return course;
}
public void setCourse(Map<String, T_Crouse> course) {
  this.course = course;
}

}

T_course类：

package server.com.upc.test;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Entity
public class T_Crouse {
private int  id;
private String name;

@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;
}

}

中间表Score也写成实体类：

package server.com.upc.test;

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

@Entity

@Table(name="score")
public class T_Score {
private int  id;
private int  scrores;
private T_Student student;
private T_Crouse  course;

@Id
@GeneratedValue
public int getId() {
  return id;
}
public int getScrores() {
  return scrores;
}
public void setScrores(int scrores) {
  this.scrores = scrores;
}
public void setId(int id) {
  this.id = id;
}

@ManyToOne
@JoinColumn(name="student_id")
public T_Student getStudent() {
return student;
}

public void setStudent(T_Student student) {
this.student = student;
}
@ManyToOne
@JoinColumn(name="course_id")
public T_Crouse getCourse() {
return course;
}

public void setCourse(T_Crouse course) {
this.course = course;
}

}

注意的是中间表中的导航关系manytomany @JoinColumn(name="course_id")；@JoinColumn(name="course_id")中声明的course_id，student_id和T_student表中声明的要一致,不然会产生其他的字段--再就是中间表的@Table(name="score")score名字和T_Student中的 @JoinTable(
name="score",要一样！！！

建立好之后就会生成中间表含有字段id，student_id,course_id，和score四个字段（然后hibernate生成的主键是（student_id,coure_id））虽然你在T_Score表中声明了自己的id。。。。这是值得注意的地方！

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