974
第十章 基於Annotation的關係映射 多對一與一對多
如果下麵部分內容有不明白的可以查找：
基於Annotation的關係映射 前期準備:https://blog.csdn.net/p_3er/article/details/9061911
基於xml的多對一:https://blog.csdn.net/p_3er/article/details/9036759
基於xml的一對多:https://blog.csdn.net/p_3er/article/details/9036921
本文是把多對一與一對多結合起來了，形成一個雙向的映射。如果隻想要單向的話，把別外一邊的注解去掉就是了。
Department:
@Entity
@Table(name = "department", catalog = "hibernate")
public class Department implements java.io.Serializable {
private Integer id;
private String name;
private Set<Employee> employees = new HashSet<Employee>(0);
public Department() {
}
public Department(String name, Set<Employee> employees) {
this.name = name;
this.employees = employees;
}
@Id
@GeneratedValue
@Column(name = "id", unique = true, nullable = false)
public Integer getId() {
return this.id;
}
public void setId(Integer id) {
this.id = id;
}
@Column(name = "name", nullable = false, length = 45)
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "department")
/*
一對多。
department和employee的一對多關係中,當指定department中的mappedBy後,關係隻能被employee來主動維護.也就是employee級聯的處理department.
之前的映射文件：
<set name="employees" inverse="false" cascade="all">
<key column="department_id"></key>
<one-to-many />
</set>
*/
public Set<Employee> getEmployees() {
return this.employees;
}
public void setEmployees(Set<Employee> employees) {
this.employees = employees;
}
}
Employee:
@Entity
@Table(name = "employee", catalog = "hibernate")
public class Employee implements java.io.Serializable {
private Integer id;
private Department department;
private String name;
public Employee() {
}
@Id
@GeneratedValue
@Column(name = "id", unique = true, nullable = false)
public Integer getId() {
return this.id;
}
public void setId(Integer id) {
this.id = id;
}
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "department_id")
/*
多對一。
<many-to-one name="department" column="department_id"></many-to-one>
*/
public Department getDepartment() {
return this.department;
}
public void setDepartment(Department department) {
this.department = department;
}
@Column(name = "name", nullable = false, length = 45)
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
}
最後更新：2017-04-03 18:52:11