Hibernate 树状映射简单模拟

树状结构的设计

在同—个类中使用OneToMany和ManyTo0ne

参考下面代码：

@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(cascade=CascadeType.ALL, mappedBy="parent")

        // fetch=FetchType.EAGER可省略即为@OneToMany的默认值fetch=FetchType.LAZY

        // 若树形较小可使用EAGER 一次全部载入内存

        // 若为LAZY则查询树形时不会一次全部载入内存(适用于较大的树形),会每取一个叶子节点就select一次

public Set<Org> getChildren() {
return children;
}

public void setChildren(Set<Org> children) {
this.children = children;
}

@ManyToOne
@JoinColumn(name="parent_id")
public Org getParent() {
return parent;
}

public void setParent(Org parent) {
this.parent = parent;
}
}

测试代码如下：

@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 o = (Org)session.load(Org.class, 1);
print(o, 0);// 打印出简单的树状结构
session.getTransaction().commit();
session.close();

}

private void print(Org o, int level) {

String preStr = "";
for(int i=0; i<level; i++) {
preStr += "----";
}
System.out.println(preStr + o.getName());
for(Org child : o.getChildren()) {
print(child, level+1);// 递归
}

}