Java笔记之hibernate(八):多对多
0.说在前面
1.修改Employee类,添加Project类的Set集合属性projects
package com.hibernate.demo.bean; import java.util.Set; public class Employee { private Integer empId; private String empName; private Department department; private Set<Project> projects; public Employee() { } public Employee(Integer empId, String empName, Department department, Set<Project> projects) { super(); this.empId = empId; this.empName = empName; this.department = department; this.projects = projects; } public Integer getEmpId() { return empId; } public void setEmpId(Integer empId) { this.empId = empId; } public String getEmpName() { return empName; } public void setEmpName(String empName) { this.empName = empName; } public Department getDepartment() { return department; } public void setDepartment(Department department) { this.department = department; } public Set<Project> getProjects() { return projects; } public void setProjects(Set<Project> projects) { this.projects = projects; } }
2.修改Employee.hbm.xml文件,添加多对多配置
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="com.hibernate.demo.bean"> <!-- 映射Employee类与t_employee表 --> <class name="Employee" table="t_employee"> <id name="empId" column="emp_id"> <!-- 声明主键生成策略为自增 --> <generator class="native"></generator> </id> <property name="empName" column="emp_name"></property> <!-- 多对一,name指定多的一方中一的一方的属性名称,class指定一的一方类名,column指定多的一方表中指向一的一方表的外键字段 --> <many-to-one name="department" class="Department" column="dept_id"></many-to-one> <!-- 用于配置多对多的关系,table用于指定中间表的表名 --> <set name="projects" table="t_peitem"> <!-- 中间表用于指向Employee对应表的外键列名--> <key column="emp_id"></key> <!-- 声明多对多的关系,column用于指定中间表指向Project类对应表的外键列名 ,class指定多的另一方的类名--> <many-to-many column="pro_id" class="Project"></many-to-many> </set> </class> </hibernate-mapping>
3.新建Project类
package com.hibernate.demo.bean; import java.util.Set; public class Project { private Integer proId; private String proName; private Set<Employee> employees; public Project() { } public Project(Integer proId, String proName, Set<Employee> employees) { super(); this.proId = proId; this.proName = proName; this.employees = employees; } public Integer getProId() { return proId; } public void setProId(Integer proId) { this.proId = proId; } public String getProName() { return proName; } public void setProName(String proName) { this.proName = proName; } public Set<Employee> getEmployees() { return employees; } public void setEmployees(Set<Employee> employees) { this.employees = employees; } }
4.新建Project.hbm.xml文件
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="com.hibernate.demo.bean"> <!-- 映射Project类与表t_project --> <class name="Project" table="t_project"> <id name="proId" column="pro_id"> <!-- 指定主键生成策略为自增 --> <generator class="native"></generator> </id> <property name="proName" column="pro_name"></property> <!-- 用于配置多对多的关系,table用于指定中间表的表名 --> <set name="employees" table="t_peitem"> <!-- 中间表指向 Project类对应表的外键列名--> <key column="pro_id"></key> <!-- 声明多对多的关系,column指定中间表指向Employee类对应表的外键列名, class指向多的另一方的类名--> <many-to-many column="emp_id" class="Employee"></many-to-many> </set> </class> </hibernate-mapping>
5.修改hibernate.cfg.xml文件,添加Project.hbm.xml映射配置
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <!-- 数据库连接配置 --> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url">jdbc:mysql://localhost:3306/keeper?characterEncoding=utf-8</property> <property name="connection.username">root</property> <property name="connection.password">123456</property> <!-- MySQL方言配置 --> <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property> <property name="show_sql">true</property> <property name="hbm2ddl.auto">update</property> <mapping resource="com/hibernate/demo/bean/Employee.hbm.xml"/> <mapping resource="com/hibernate/demo/bean/Department.hbm.xml"/> <mapping resource="com/hibernate/demo/bean/Project.hbm.xml"/> </session-factory> </hibernate-configuration>
6.新建ManyTOManyTest类
package com.hibernate.demo.test; import java.util.Set; import org.hibernate.SessionFactory; import org.hibernate.Transaction; import org.hibernate.cfg.Configuration; import org.hibernate.classic.Session; import com.hibernate.demo.bean.Employee; import com.hibernate.demo.bean.Project; public class ManyToManyTest { public static void main(String[] args) { //加载配置文件,创建会话工厂对象 SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory(); //创建会话对象 Session session = sessionFactory.openSession(); //开启事务 Transaction transaction = session.beginTransaction(); //根据id获取Employee对象 Employee employee1 = (Employee) session.get(Employee.class, 17); Employee employee2=(Employee) session.get(Employee.class, 18); //新建项目 Project project1=new Project(); project1.setProName("项目五"); session.save(project1); Project project2=new Project(); project2.setProName("项目六"); session.save(project2); //设置项目 Set<Project> projects = employee1.getProjects(); projects.add(project1); projects.add(project2); session.update(employee1); Set<Project> projects2 = employee2.getProjects(); projects2.add(project1); projects2.add(project2); session.update(employee2); //提交事务 transaction.commit(); //关闭会话 session.close(); //关闭会话工厂 sessionFactory.close(); } }
7.运行ManyTOManyTest类,查看数据库
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder". SLF4J: Defaulting to no-operation (NOP) logger implementation SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details. Hibernate: select employee0_.emp_id as emp1_0_0_, employee0_.emp_name as emp2_0_0_, employee0_.dept_id as dept3_0_0_ from t_employee employee0_ where employee0_.emp_id=? Hibernate: select employee0_.emp_id as emp1_0_0_, employee0_.emp_name as emp2_0_0_, employee0_.dept_id as dept3_0_0_ from t_employee employee0_ where employee0_.emp_id=? Hibernate: insert into t_project (pro_name) values (?) Hibernate: insert into t_project (pro_name) values (?) Hibernate: select projects0_.emp_id as emp1_0_1_, projects0_.pro_id as pro2_1_, project1_.pro_id as pro1_3_0_, project1_.pro_name as pro2_3_0_ from t_peitem projects0_ inner join t_project project1_ on projects0_.pro_id=project1_.pro_id where projects0_.emp_id=? Hibernate: select projects0_.emp_id as emp1_0_1_, projects0_.pro_id as pro2_1_, project1_.pro_id as pro1_3_0_, project1_.pro_name as pro2_3_0_ from t_peitem projects0_ inner join t_project project1_ on projects0_.pro_id=project1_.pro_id where projects0_.emp_id=? Hibernate: insert into t_peitem (emp_id, pro_id) values (?, ?) Hibernate: insert into t_peitem (emp_id, pro_id) values (?, ?) Hibernate: insert into t_peitem (emp_id, pro_id) values (?, ?) Hibernate: insert into t_peitem (emp_id, pro_id) values (?, ?)
t_project表
t_peitem表按照emp_id升序排列
t_peitem表按照pro_id升序排列
