/**
- @author StormMaybin
- @date 2017-01-17
*/
一对多映射关系
有两种方式实现一对多的单向关联。一种是在只使用@OneToMany来标识,这种方式是通过一张第三方表来保存关系。还有一种是使用@OneToMany和@JoinColumn来标注,这种方式是在多的一方(Employee)的表中增加一个外键列来保存关系。
OneToMany
package com.stormma.model;
import java.util.List;
import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
/**
- Created by mayongbin01 on 2017/1/17.
*/
@Entity
@Table(name = "company")
public class Company {
//唯一标识公司
@Id
@GeneratedValue
private int id;
//公司名字
private String name;
@OneToMany(cascade = {CascadeType.ALL})
private List<Employee> employees;
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;
}
}
package com.stormma.model;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;
/**
- Created by mayongbin01 on 2017/1/17.
*/
@Entity
@Table(name = "employee")
public class Employee {
//唯一标识雇员
@Id
@GeneratedValue
private int id;
private String 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;
}
}
CREATE TABLE `employee` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
DROP TABLE IF EXISTS company
;
CREATE TABLE company
(
id
int(11) NOT NULL AUTO_INCREMENT,
name
varchar(255) DEFAULT NULL,
PRIMARY KEY (id
)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
DROP TABLE IF EXISTS company_employees
;
CREATE TABLE company_employees
(
company_id
int(11) NOT NULL,
employees_id
int(11) NOT NULL,
UNIQUE KEY UK_lg2r1rg13q18sa62l1y7un4or
(employees_id
),
KEY FKd66w6jx84tydyd8sf9mpqh5je
(company_id
),
CONSTRAINT FKd66w6jx84tydyd8sf9mpqh5je
FOREIGN KEY (company_id
) REFERENCES company
(id
),
CONSTRAINT FKnntnqhhla66c4h9ddbnlvqk2x
FOREIGN KEY (employees_id
) REFERENCES employee
(id
)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
OneToMany+JoinColumn
package com.stormma.model;
import java.util.List;
import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.Table;
/**
- Created by mayongbin01 on 2017/1/17.
*/
@Entity
@Table(name = "company")
public class Company {
//唯一标识公司
@Id
@GeneratedValue
private int id;
//公司名字
private String name;
@OneToMany(cascade = CascadeType.ALL)
@JoinColumn(name = "company_id")
private List<Employee> employees;
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;
}
}
package com.stormma.model;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;
/**
- Created by mayongbin01 on 2017/1/17.
*/
@Entity
@Table(name = "employee")
public class Employee {
//唯一标识雇员
@Id
@GeneratedValue
private int id;
private String 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;
}
}
Hibernate: create table company (id integer not null auto_increment, name varchar(255), primary key (id))
Hibernate: create table employee (id integer not null auto_increment, name varchar(255), company_id integer, primary key (id))
Hibernate: alter table employee add constraint FK5v50ed2bjh60n1gc7ifuxmgf4 foreign key (company_id) references company (id)
原文地址:https://www.jianshu.com/p/0a2163273b3e