使用hibernate实现树形结构无限级分类

session.createQuery(" from " + cls.getName() + 
" where enabled=? and parent_id is null order by id"); 

CountryTree extends BaseTree(abstract class) 
BaseTree(abstract class) implements Tree(interface) 

/**   
* 实现了树的基本操作，上溯、下溯、子节点的添加/移除和递归查找、对象关联等   
*/   
package test.testtree.base;    
import java.util.Set;    

public interface Tree {     
public String getCode();    
public String getName();    
public String getDescription();    
public Tree getParent();    
public boolean isRoot();    
public boolean isLeaf();    
public boolean isParentOf(Tree tree);    
public boolean isChildOf(Tree tree);    
public void addChild(Tree tree);    
public void rmChild(Tree tree);    
public Set getAllChildren();    
public Set getChildren();    
public Set getAllLeaves();    
public void addObject(Object obj);    
public void rmObject(Object obj);    
public Set getObjects();    
public Long getId();    
}   

package test.testtree.base;    
import java.util.*;    

public abstract class BaseTree extends BasePojo implements Tree{        
protected String code;        
protected String name;        
protected String description;            
protected BaseTree parent;       
protected Set children = new HashSet();        
protected Set objects = new HashSet();        
public void setCode(String code) {    
this.code = code;    
}        
abstract public String getCode();    
public void setName(String name) {    
this.name = name;    
}        
abstract public String getName();        
public void setDescription(String description) {    
this.description = description;    
}    
abstract public String getDescription();    
abstract public Tree getParent();            
public boolean isRoot() {    
return (getParent()==null);    
}        
public boolean isLeaf() {    
return (this.getChildren().size()==0);    
}        
public boolean isParentOf(Tree tree) {    
if (tree==null || ((BaseTree) tree).equals(this)) {    
/*如果对方为空*/   
return false;    
}else if(this.isLeaf()){    
/*如果自己为叶子,则返回FALSE*/   
return false;    
}else if(tree.isRoot()){    
/*如果对方为根,返回FALSE*/   
return false;    
}else{    
BaseTree bt = (BaseTree) (tree.getParent());    
if (this.equals(bt)){    
/*如果对方的父节点是自己,则返回TRUE*/   
return true;    
}else{    
/*判断对方的父节点是否是自己的孩子,进行递归*/   
return isParentOf(bt);    
}    
}    
}    
public boolean isChildOf(Tree tree) {    
return (tree.isParentOf(this));    
}    
public void addChild(Tree tree) {    
children.add(tree);    
}    
public void rmChild(Tree tree) {    
children.remove(tree);    
((BaseTree) tree).setParent(null);    
}    
public Set getAllLeaves() {    
Set set_old = this.getAllChildren();    
Set set = new HashSet();    
set.addAll(set_old);    
Iterator itr = set_old.iterator();    
while(itr.hasNext()){    
BaseTree bt = (BaseTree) itr.next();    
if (! bt.isLeaf()){    
set.remove(bt);    
}    
}    
return set;    
}            
public Set getAllChildren() {    
Set set = new HashSet();    
Stack stack = new Stack();    
stack.push(this);    
while(!stack.empty()){    
BaseTree bt = (BaseTree) stack.pop();    
set.add(bt);    
Iterator itr = bt.getChildren().iterator();    
while(itr.hasNext()){    
BaseTree btchild = (BaseTree) itr.next();    
stack.push(btchild);    
}    
}    
set.remove(this);    
return set;    
}        
public List getMeAndListAllChildren() {            
List lst = new Vector();    
lst.add(this);    
Iterator itr = this.getChildren().iterator();    
while(itr.hasNext()){    
BaseTree bt = (BaseTree) itr.next();    
lst.addAll(bt.getMeAndListAllChildren());                   
}            
return lst;    
}    
abstract public Set getChildren();    
public void addObject(Object obj) {    
objects.add(obj);    
}    
public void rmObject(Object obj) {    
objects.remove(obj);    
}    
abstract public Set getObjects();    
public void setParent(Tree parent) {    
this.parent = (BaseTree) parent;    
}    
public void setChildren(Set children) {    
this.children = children;    
}    
public void setObjects(Set objects) {    
this.objects = objects;    
}        
}