Hibernate关联映射---多对一实例分析(单项关联)
Hibernate关联映射---多对一实例分析(单项关联)
一 关联映射类型
1．多对一(Employee - Department)
多对一关联是一个部门可以有多个员工
所用到的映射文件为：
<many-to-one name="depart" column="depart_id"/>
二 代码分析
1．首先创建两个类，Department和Employee，并把他们关联起来
（1）Department类
package com.hbsi.domain;
//部门类
public class Department {
private int id;
private String name;
public Department() {
super();
// TODO Auto-generated constructor stub
}
public Department(int id, String name) {
super();
this.id = id;
this.name = name;
}
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;
}
public String toString() {
return "Department [id=" + id + ", name=" + name + "]";
}
}
（2）Employee类
package com.hbsi.domain;
//员工类 一般主鍵是建在多的一方
public class Employee {
private int id;
private String name;
// 得到的是一个 对象，可以得到员工对应的部门的详细信息
private Department depart;
public Employee() {
super();
// TODO Auto-generated constructor stub
}
public Employee(int id, String name, Department depart) {
super();
this.id = id;
this.name = name;
this.depart = depart;
}
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;
}
public Department getDepart() {
return depart;
}
public void setDepart(Department depart) {
this.depart = depart;
}
public String toString() {
return "Employee [id=" + id + ", name=" + name + ", depart=" + depart
+ "]";
}
}
注：之所以在员工表中设主键是为了减少资源消耗，而如果设置
private int depart_id;
通过员工查找部门的话，只能找到部门的id,得不到部门的其他信息 ，
设置的Deparment的类对象作为外键，可以得到部门的所有信息
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