Hibernate_映射_关联关系_多对多映射2

你的名字 2022-06-16 05:49 209阅读 0赞

package cn.itcast.g_hbm_manyToMany;
    
    import java.util.HashSet;
    import java.util.Set;
    
    /**
     * 学生
     * 
     * @author 风清杨
     * @version V1.0
     */
    public class Student {
    	private Long id;
    	private String name;
    	private Set
       
         teachers = new HashSet
        
         ();// 关联得老师位
    
    	public Long getId() {
    		return id;
    	}
    
    	public void setId(Long id) {
    		this.id = id;
    	}
    
    	public String getName() {
    		return name;
    	}
    
    	public void setName(String name) {
    		this.name = name;
    	}
    
    	public Set
         
           getTeachers() {
    		return teachers;
    	}
    
    	public void setTeachers(Set
          
            teachers) {
    		this.teachers = teachers;
    	}
    
    	@Override
    	public String toString() {
    		return "Student [id=" + id + ", name=" + name + "]";
    	}
    
    }
    package cn.itcast.g_hbm_manyToMany;
    
    import java.util.HashSet;
    import java.util.Set;
    
    /**
     * 老师
     * 
     * @author 风清杨
     * @version V1.0
     */
    public class Teacher {
    	private Long id;
    	private String name;
    	private Set
           
             students = new HashSet
            
             ();// 关联的学生们 public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Set
             
               getStudents() { return students; } public void setStudents(Set
              
                students) { this.students = students; } @Override public String toString() { return "Teacher [id=" + id + ", name=" + name + "]"; } } private static SessionFactory sessionFactory = new Configuration()// .configure()// .addClass(Student.class)// 添加Hibernate实体类(加载对应的映射文件) .addClass(Teacher.class)// 添加Hibernate实体类(加载对应的映射文件) .buildSessionFactory();

package cn.itcast.g_hbm_manyToMany;
    
    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(Student.class)// 添加Hibernate实体类(加载对应的映射文件)
    			.addClass(Teacher.class)// 添加Hibernate实体类(加载对应的映射文件)
    			.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();
    			// ------------------------------------
    
    			// 构建老师对象
    			Teacher teachers1 = new Teacher();
    			teachers1.setName("张老师");
    			Teacher teachers2 = new Teacher();
    			teachers2.setName("赵老师");
    
    			// 构建学生对象
    			Student students1 = new Student();
    			students1.setName("王小明");
    			Student students2 = new Student();
    			students2.setName("李冰冰");
    
    			// 关联起来
    			students1.getTeachers().add(teachers1);
    			students1.getTeachers().add(teachers2);
    			students2.getTeachers().add(teachers2);
    
    			teachers1.getStudents().add(students1);
    			teachers2.getStudents().add(students1);
    			teachers2.getStudents().add(students2);
    
    			// 保存
    			session.save(students1);
    			session.save(students2);
    			session.save(teachers1);
    			session.save(teachers2);
    			// ------------------------------------
    			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
    			Teacher teacher = (Teacher) session.get(Teacher.class, 2L);
    			System.out.println(teacher);
    			System.out.println(teacher.getStudents());
    
    			// ------------------------------------
    			tx.commit();
    		} catch (RuntimeException e) {
    			tx.rollback();
    			throw e;
    		} finally {
    			session.close();
    		}
    	}
    
    	// 解除关联关系
    	@Test
    	public void testRemoveRelation() throws Exception {
    		Session session = sessionFactory.openSession();
    		Transaction tx = null;
    		try {
    			tx = session.beginTransaction();
    			// ------------------------------------
    			// 如果inverse=false就可以解除,如果为true就不可以解除
    			Teacher teacher = (Teacher) session.get(Teacher.class, 2L);
    			teacher.getStudents().clear();
    
    			// ------------------------------------
    			tx.commit();
    		} catch (RuntimeException e) {
    			tx.rollback();
    			throw e;
    		} finally {
    			session.close();
    		}
    	}
    
    	// 删除对象,对关联对象的影响
    	@Test
    	public void testDelete() throws Exception {
    		Session session = sessionFactory.openSession();
    		Transaction tx = null;
    		try {
    			tx = session.beginTransaction();
    			// ------------------------------------
    			// 删除部门方(一方)
    			// a,如果没有关联的对方：
    			// b,如果有关联的对方且inverse=false,由于可以维护关联关系,它就会先删除关联关系,再删除自已。
    			// c,如果有关联的对方且inverse=true,由于不能维护关联关系,所以会直接执行删除自已,就会有异常。
    			Teacher teacher = (Teacher) session.get(Teacher.class, 6L);
    			session.delete(teacher);
    			
    			// ------------------------------------
    			tx.commit();
    		} catch (RuntimeException e) {
    			tx.rollback();
    			throw e;
    		} finally {
    			session.close();
    		}
    	}
    }