建表语句：
DROP TABLE IF EXISTS `t_company`; CREATE TABLE `t_company` ( `companyId` int(10) unsigned NOT NULL AUTO_INCREMENT, `companyName` varchar(30) NOT NULL, PRIMARY KEY (`companyId`) ) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=gb2312; INSERT INTO `t_company` VALUES (‘1‘, ‘Sun‘); INSERT INTO `t_company` VALUES (‘2‘, ‘Apache‘); DROP TABLE IF EXISTS `t_employee`; CREATE TABLE `t_employee` ( `employeeId` int(10) unsigned NOT NULL AUTO_INCREMENT, `employeeName` varchar(15) NOT NULL, `cid` int(10) unsigned NOT NULL, PRIMARY KEY (`employeeId`) ) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=gb2312; INSERT INTO `t_employee` VALUES (‘1‘, ‘Tom‘, ‘1‘); INSERT INTO `t_employee` VALUES (‘2‘, ‘Summ‘, ‘1‘); INSERT INTO `t_employee` VALUES (‘3‘, ‘Cat‘, ‘2‘); INSERT INTO `t_employee` VALUES (‘4‘, ‘Vinylon‘, ‘1‘); INSERT INTO `t_employee` VALUES (‘5‘, ‘Dog‘, ‘2‘);
Employee.java
package com.fancy.po;
import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
@Entity
@Table(name = "t_employee")
public class Employee {
private Integer employeeId;
private String employeeName;
private Company company;
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
public Integer getEmployeeId() {
return employeeId;
}
/**
* @ManyToOne：多对一,cascade：级联,请参考上一篇
* fetch = FetchType.LAZY,延迟加载策略,如果不想延迟加载可以用FetchType.EAGER
*/
@ManyToOne(cascade = {CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH},fetch = FetchType.LAZY)
@JoinColumn(name = "cid")
public Company getCompany() {
return company;
}
public String getEmployeeName() {
return employeeName;
}
public void setEmployeeId(Integer employeeId) {
this.employeeId = employeeId;
}
public void setEmployeeName(String employeeName) {
this.employeeName = employeeName;
}
public void setCompany(Company company) {
this.company = company;
}
}
Company.java
package com.fancy.po;
import java.util.Set;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
@Entity
@Table(name = "t_company")
public class Company {
private Integer companyId;
private String companyName;
private Set<Employee> employees;
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
public Integer getCompanyId() {
return companyId;
}
/**
* @OneToMany 与 OneToOne相似的也用mappedBy,参考了Employee
*/
@OneToMany(mappedBy = "company")
public Set<Employee> getEmployees() {
return employees;
}
public String getCompanyName() {
return companyName;
}
public void setCompanyId(Integer companyId) {
this.companyId = companyId;
}
public void setCompanyName(String companyName) {
this.companyName = companyName;
}
public void setEmployees(Set<Employee> employees) {
this.employees = employees;
}
}
Test.java
package com.fancy.test;
import java.util.Iterator;
import java.util.Set;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.cfg.Configuration;
import com.fancy.po.Company;
import com.fancy.po.Employee;
public class Test {
public static void main(String[] args) {
//读取hibernate配置,默认读取classpath下的hibernate.cfg.xml
Configuration conf = new AnnotationConfiguration();
//构建session工厂
SessionFactory sessionFactory = conf.configure().buildSessionFactory();
//打开session
Session session = sessionFactory.openSession();
//开始事务
session.beginTransaction();
// * * * * * * * * * * * * * * * * * * * * * * * * * * * *
//test1(session); //测试 1
//test2(session); //测试 2
test3(session); //测试 3
// * * * * * * * * * * * * * * * * * * * * * * * * * * * *
//提交事务
session.getTransaction().commit();
//关闭session工厂
sessionFactory.close();
//关闭session
session.close();
}
public static void test1(Session session){
Company company = (Company)session.get(Company.class, 1); //发出Company的select语句
Set<Employee> employee = company.getEmployees(); //不发出Employee的select语句
System.out.println("Company ：" + company.getCompanyName());
System.out.println("CountSum：" + employee.size()); //Employee初次被使用,发出select语句
Iterator<Employee> it = employee.iterator(); //Employee不再发出select语句
while(it.hasNext()){
System.out.println("EmployeeName：" + it.next().getEmployeeName());
}
}
public static void test2(Session session){
Company company = (Company)session.get(Company.class, 2);//发出Company的select语句
Set<Employee> employee = company.getEmployees(); //不发出Employee的select语句
Iterator<Employee> it = employee.iterator(); //发出Employee的select语句
Employee e = null;
Boolean first = false;
while(it.hasNext()){
e = it.next();
if(!first){
System.out.println("EmployeeId：[" + e.getEmployeeId() + "] information will be change");
e.setEmployeeName("fancy"); //更改雇员名字
// session.save(e); //发出Employee的update语句,不发出Company的update语句
session.save(company); //发出Employee的update语句,不发出Company的update语句
first = true;
}
System.out.println("EmployeeName：" + e.getEmployeeName());
}
}
public static void test3(Session session){
Employee employee = (Employee)session.get(Employee.class, 1);//发出Employee的select语句
Company company = (Company)session.get(Company.class, 1);//发出Company的select语句
company.setCompanyName("Oracle"); //更改公司名字
// session.save(company);//发出Company的update语句,不发出Employee的update语句
session.save(employee);//发出Company的update语句,不发出Employee的update语句
}
}
原文地址：hibernate one-to-many many-to-one 双向注解参考：
hibernate annotation 之 一对一 单/双 向外键关联
hibernate annotation 之 一对多单向外键关联
hibernate annotation 之 多对一单向外键关联
hibernate annotation 之 一对多、多对一双向外键关联
hibernate one-to-many many-to-one 双向注解
时间： 2024-07-29 13:59:44