Hibernate学习笔记_关系映射_树状结构练习
1 树状结构的设计(至关重要)
a) 在同—个类中使用One2Many和Many20ne
@Entity public class Org { private int id; private String name; private Set<Org> children=new HashSet<Org>(); private Org parent; @Id @GeneratedValue 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; } @OneToMany(mappedBy="parent",cascade={CascadeType.ALL},fetch=FetchType.EAGER) public Set<Org> getChildren() { return children; } public void setChildren(Set<Org> children) { this.children = children; } @ManyToOne() @JoinColumn(name="parentID") public Org getParent() { return parent; } public void setParent(Org parent) { this.parent = parent; } }
@Test public void testSave() { Org o = new Org(); o.setName("总公司"); Org o1 = new Org(); o1.setName("分公司1"); Org o2 = new Org(); o2.setName("分公司2"); Org o11 = new Org(); o11.setName("分公司1下部门1"); Org o12 = new Org(); o12.setName("分公司1下部门2"); o.getChildren().add(o1); o.getChildren().add(o2); o1.getChildren().add(o11); o1.getChildren().add(o12); o11.setParent(o1); o12.setParent(o1); o1.setParent(o); o2.setParent(o); Session session = sessionFactory.openSession(); session.beginTransaction(); session.save(o); session.getTransaction().commit(); session.close(); } @Test public void testLoad() { testSave(); Session session = sessionFactory.openSession(); session.beginTransaction(); Org org=(Org)session.load(Org.class, 1); print(org,0); session.getTransaction().commit(); session.close(); } private void print(Org org,int level) { String str=""; for(int i=0;i<level;i++){ str+="----"; } System.out.println(str+org.getName()); for (Org o:org.getChildren()){ print(o,level+1); } }