Hibernate_映射_关联关系_一对多多对一映射1

秒速五厘米 2022-06-16 05:38 302阅读 0赞

值类型的集合
    	集合元素是普通类型
    实体类型的集合
    	集合元素是另外一个实体
    
    	一对多								     多对一
    Department.hbm.xml							Employee.hbm.xml
    	要说明的信息有：						要说明的信息有：
    	1,集合表(员工表)							1,关联的是什么类型
    	2,集合外键								2,外键列
    	3,集合元素 									
    		关联的实例类型

部门映射文件

<?xml version="1.0"?>
    <!DOCTYPE hibernate-mapping PUBLIC
            "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
            "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
    
    <hibernate-mapping package="cn.itcast.f_hbm_oneToMany">
    	
    	<class name="Department" table="department">
    		<id name="id" type="integer" column="id_">
    			<generator class="native" />
    		</id>
    		<property name="name" type="string" column="name_" />
    		
    		<set name="employee">
    			<key column="departmentId" />
    			<one-to-many class="Employee" />
    		</set>
    	</class>
    </hibernate-mapping>

员工映射文件

<?xml version="1.0"?>
    <!DOCTYPE hibernate-mapping PUBLIC
            "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
            "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
    
    <hibernate-mapping package="cn.itcast.f_hbm_oneToMany">
    	
    	<class name="Employee" table="employee">
    		<id name="id" type="integer" column="id_">
    			<generator class="native" />
    		</id>
    		<property name="name" type="string" column="name_" />
    
    		
    		<many-to-one name="department" class="Department" column="departmentId"></many-to-one>
    	</class>
    </hibernate-mapping>

部门实例

package cn.itcast.f_hbm_oneToMany;
    
    import java.util.HashSet;
    import java.util.Set;
    
    /**
     * 部门
     * 
     * @author 风清杨
     * @version V3.0
     * 
     */
    public class Department {
    	/** 部门id */
    	private Integer id;
    	/** 部门名称 */
    	private String name;
    	/** 员工信息 */
    	private Set<Employee> employee = new HashSet<Employee>();// 关联的很多员工
    
    	public Integer getId() {
    		return id;
    	}
    
    	public void setId(Integer id) {
    		this.id = id;
    	}
    
    	public String getName() {
    		return name;
    	}
    
    	public void setName(String name) {
    		this.name = name;
    	}
    
    	public Set<Employee> getEmployee() {
    		return employee;
    	}
    
    	public void setEmployee(Set<Employee> employee) {
    		this.employee = employee;
    	}
    
    	@Override
    	public String toString() {
    		return "Department [id=" + id + ", name=" + name + "]";
    	}
    
    }

员工实例

package cn.itcast.f_hbm_oneToMany;
    
    /**
     * 员工部门
     * 
     * @author 风清杨
     * @version V3.0
     * 
     */
    public class Employee {
    	/** 员工编号 */
    	private Integer id;
    	/** 员工姓名 */
    	private String name;
    
    	/** 员工部门 */
    	private Department department;// 关联的部门对象
    
    	public Integer getId() {
    		return id;
    	}
    
    	public void setId(Integer id) {
    		this.id = id;
    	}
    
    	public String getName() {
    		return name;
    	}
    
    	public void setName(String name) {
    		this.name = name;
    	}
    
    	public Department getDepartment() {
    		return department;
    	}
    
    	public void setDepartment(Department department) {
    		this.department = department;
    	}
    
    	@Override
    	public String toString() {
    		return "Employee [id=" + id + ", name=" + name + "]";
    	}
    
    }

测试类

package cn.itcast.f_hbm_oneToMany;
    
    import org.hibernate.Session;
    import org.hibernate.SessionFactory;
    import org.hibernate.Transaction;
    import org.hibernate.cfg.Configuration;
    import org.junit.Test;
    
    /**
     * 应用程序操作类
     * 
     * @author 风清杨
     * @version V3.0
     * 
     */
    public class App {
    	private static SessionFactory sessionFactory = new Configuration()//
    			.configure()//
    			.addClass(Department.class)//
    			.addClass(Employee.class)//
    			.buildSessionFactory();
    
    	// 保存,有关联关系
    	@Test
    	public void testSave() throws Exception {
    		Session session = sessionFactory.openSession();
    		Transaction tx = null;
    		try {
    			tx = session.beginTransaction();
    			// ------------------------------------
    
    			// 新建对象
    			Department department = new Department();
    			department.setName("开发部");
    
    			Employee employee1 = new Employee();
    			employee1.setName("张三");
    
    			Employee employee2 = new Employee();
    			employee2.setName("李四");
    
    			// 关联起来
    			employee1.setDepartment(department);
    			employee2.setDepartment(department);
    			department.getEmployee().add(employee1);
    			department.getEmployee().add(employee2);
    
    			// 保存
    			session.save(department);
    			session.save(employee1);
    			session.save(employee2);
    			// ------------------------------------
    			tx.commit();
    		} catch (RuntimeException e) {
    			tx.rollback();
    			throw e;
    		} finally {
    			session.close();
    		}
    	}
    
    	// 获取,可以获取到关联的对方
    	@Test
    	public void testGet() throws Exception {
    		Session session = sessionFactory.openSession();
    		Transaction tx = null;
    		try {
    			tx = session.beginTransaction();
    			// ------------------------------------
    
    			// 获取一方数据,并显示另一方信息
    			//Department department = (Department) session.get(Department.class,
    			// 1);
    			// System.out.println(department);
    			// System.out.println(department.getEmployee());
    			Employee employee = (Employee) session.get(Employee.class, 1);
    			System.out.println(employee);
    			System.out.println(employee.getDepartment());
    
    			// ------------------------------------
    			tx.commit();
    		} catch (RuntimeException e) {
    			tx.rollback();
    			throw e;
    		} finally {
    			session.close();
    		}
    	}
    }