为Extjs 树提供数据的递归算法

最新推荐文章于 2019-06-01 23:28:00 发布

转载最新推荐文章于 2019-06-01 23:28:00 发布 · 589 阅读

文章标签：

#extjs #recursion #list #iterator #string #json

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本文介绍了一种使用Java递归方法构建JSON树形结构的方法。通过定义Node类及其属性，手动创建List集合来模拟从数据库获取的数据，再利用递归函数实现树形结构的JSON字符串构建。

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（转自：http://emlyn1180.iteye.com/blog/315334 ）

首先先建立Node模型

public class Node {
	private int id;
	private int parentId;
	Node(){}
	Node(int id,int parentId){
		this.id=id;
		this.parentId = parentId;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public int getParentId() {
		return parentId;
	}
	public void setParentId(int parentId) {
		this.parentId = parentId;
	}
}

下面这个类先手工建立List，在实际应用中是从数据库读取List，然后再Main方法里调用递归方法，得到Json字符串

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;


public class Recursion {
	List nodeList =new ArrayList();
	Recursion(){//构造方法里初始化模拟List
		Node node1 = new Node(1,0);  
        Node node2 = new Node(2,1);  
        Node node3 = new Node(3,1);  
        Node node4 = new Node(4,2);  
        Node node5 = new Node(5,2);  
        Node node6 = new Node(6,2);  
        Node node7 = new Node(7,6);  
        Node node8 = new Node(8,6);  
          
        nodeList.add(node1);  
        nodeList.add(node2);  
        nodeList.add(node3);  
        nodeList.add(node4);  
        nodeList.add(node5);  
        nodeList.add(node6);  
        nodeList.add(node7);  
        nodeList.add(node8);  
	}
	StringBuffer returnStr=new StringBuffer();  
    public void recursionFn(List list , Node node){  
        if(hasChild(list,node)){  
            returnStr.append("{id:");
            returnStr.append(node.getId());
            returnStr.append(",parentId:");
            returnStr.append(node.getParentId());
            returnStr.append(",children:[");  
            List childList = getChildList(list,node);  
            Iterator it = childList.iterator();  
            while(it.hasNext()){  
                Node n = (Node)it.next();  
                recursionFn(list,n);  
            }  
            returnStr.append("]},");  
        }else{  
            returnStr.append("{id:");
            returnStr.append(node.getId());
            returnStr.append(",parentId:");
            returnStr.append(node.getParentId());
            returnStr.append(",leaf:true},");  
        }  
          
    }  
    public boolean hasChild(List list, Node node){  //判断是否有子节点
    	return getChildList(list,node).size()>0?true:false;
    }
    public List getChildList(List list , Node node){  //得到子节点列表
        List li = new ArrayList();  
        Iterator it = list.iterator();  
        while(it.hasNext()){  
            Node n = (Node)it.next();  
            if(n.getParentId()==node.getId()){  
                li.add(n);  
            }  
        }  
        return li;  
    }
    public String modifyStr(String returnStr){//修饰一下才能满足Extjs的Json格式
    	return ("["+returnStr+"]").replaceAll(",]", "]");
    	
    }
    public static void main(String[] args) {  
        Recursion r = new Recursion();  
        r.recursionFn(r.nodeList, new Node(1,0));  
        System.out.println(r.modifyStr(r.returnStr.toString()));  
    }  
}

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;


public class Recursion {
	List nodeList =new ArrayList();
	Recursion(){//构造方法里初始化模拟List
		Node node1 = new Node(1,0);  
        Node node2 = new Node(2,1);  
        Node node3 = new Node(3,1);  
        Node node4 = new Node(4,2);  
        Node node5 = new Node(5,2);  
        Node node6 = new Node(6,2);  
        Node node7 = new Node(7,6);  
        Node node8 = new Node(8,6);  
          
        nodeList.add(node1);  
        nodeList.add(node2);  
        nodeList.add(node3);  
        nodeList.add(node4);  
        nodeList.add(node5);  
        nodeList.add(node6);  
        nodeList.add(node7);  
        nodeList.add(node8);  
	}
	StringBuffer returnStr=new StringBuffer();  
    public void recursionFn(List list , Node node){  
        if(hasChild(list,node)){  
            returnStr.append("{id:");
            returnStr.append(node.getId());
            returnStr.append(",parentId:");
            returnStr.append(node.getParentId());
            returnStr.append(",children:[");  
            List childList = getChildList(list,node);  
            Iterator it = childList.iterator();  
            while(it.hasNext()){  
                Node n = (Node)it.next();  
                recursionFn(list,n);  
            }  
            returnStr.append("]},");  
        }else{  
            returnStr.append("{id:");
            returnStr.append(node.getId());
            returnStr.append(",parentId:");
            returnStr.append(node.getParentId());
            returnStr.append(",leaf:true},");  
        }  
          
    }  
    public boolean hasChild(List list, Node node){  //判断是否有子节点
    	return getChildList(list,node).size()>0?true:false;
    }
    public List getChildList(List list , Node node){  //得到子节点列表
        List li = new ArrayList();  
        Iterator it = list.iterator();  
        while(it.hasNext()){  
            Node n = (Node)it.next();  
            if(n.getParentId()==node.getId()){  
                li.add(n);  
            }  
        }  
        return li;  
    }
    public String modifyStr(String returnStr){//修饰一下才能满足Extjs的Json格式
    	return ("["+returnStr+"]").replaceAll(",]", "]");
    	
    }
    public static void main(String[] args) {  
        Recursion r = new Recursion();  
        r.recursionFn(r.nodeList, new Node(1,0));  
        System.out.println(r.modifyStr(r.returnStr.toString()));  
    }  
}

Main方法运行效果如下：
[{id:1,parentId:0,children:[{id:2,parentId:1,children:[{id:4,parentId:2,leaf:true},{id:5,parentId:2,leaf:true},{id:6,par
entId:2,children:[{id:7,parentId:6,leaf:true},{id:8,parentId:6,leaf:true}]}]},{id:3,parentId:1,leaf:true}]}]
在具体的应用中稍加修改即可

（记得，return 要" return r.modifyStr(r.returnStr.toString()); "