在項目中難免會用到樹形結構，畢竟這是一種常用的組織架構。樓主這里整理了兩個實現的版本，可以直接拿來使用，非常方便。
樓主沒有單獨建項目，直接在以前的一個Demo上實現的。第一種，看下面代碼：
package com.johanChan.WebSocket.utils;
import com.alibaba.fastjson.JSON; import java.util.ArrayList; import java.util.List; //圖層結構 public class TreeBuilder { List<Node> nodes = new ArrayList<>(); public String buildTree(List<Node> nodes) { TreeBuilder treeBuilder = new TreeBuilder(nodes); return treeBuilder.buildJSONTree(); } public TreeBuilder() {} public TreeBuilder(List<Node> nodes) { super(); this.nodes = nodes; } // 構建JSON樹形結構 public String buildJSONTree() { List<Node> nodeTree = buildTree(); String jsonStr = JSON.toJSONString(nodeTree); return jsonStr; } // 構建樹形結構 public List<Node> buildTree() { List<Node> treeNodes = new ArrayList<>(); List<Node> rootNodes = getRootNodes(); for (Node rootNode : rootNodes) { buildChildNodes(rootNode); treeNodes.add(rootNode); } return treeNodes; } // 遞歸子節點 public void buildChildNodes(Node node) { List<Node> children = getChildNodes(node); if (!children.isEmpty()) { for (Node child : children) { buildChildNodes(child); } node.setChildren(children); } } // 獲取父節點下所有的子節點 public List<Node> getChildNodes(Node pnode) { List<Node> childNodes = new ArrayList<>(); for (Node n : nodes) { if (pnode.getId().equals(n.getParentId())) { childNodes.add(n); } } return childNodes; } // 判斷是否為根節點 public boolean rootNode(Node node) { boolean isRootNode = true; for (Node n : nodes) { if (node.getParentId().equals(n.getId())) { isRootNode = false; break; } } return isRootNode; } // 獲取集合中所有的根節點 public List<Node> getRootNodes() { List<Node> rootNodes = new ArrayList<>(); for (Node n : nodes) { if (rootNode(n)) { rootNodes.add(n); } } return rootNodes; } public static class Node { private Integer id; private Integer parentId; private String name; private String code; private Integer level; private List<Node> children; public Node() {} public Node(Integer id,Integer parentId,String name,String code,Integer level){ super(); this.id = id; this.parentId = parentId; this.name = name; this.code = code; this.level = level; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public Integer getParentId() { return parentId; } public void setParentId(Integer parentId) { this.parentId = parentId; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getCode() { return code; } public void setCode(String code) { this.code = code; } public Integer getLevel() { return level; } public void setLevel(Integer level) { this.level = level; } public List<Node> getChildren() { return children; } public void setChildren(List<Node> children) { this.children = children; } } }
看起來很長對嗎？沒關系，直接copy一下就可以使用。首先生成一個樹形結構的數據：
public static List<TreeBuilder.Node> buildNode(){
List<TreeBuilder.Node> nodeList = new ArrayList<>(); TreeBuilder.Node node = new TreeBuilder.Node(0,-1,"地球","WORD",1); TreeBuilder.Node node1 = new TreeBuilder.Node(1,0,"中國","CHN",1); TreeBuilder.Node node2 = new TreeBuilder.Node(2,1,"華北區域","A",2); TreeBuilder.Node node3 = new TreeBuilder.Node(3,1,"華南區域","B",2); TreeBuilder.Node node4 = new TreeBuilder.Node(4,1,"華東區域","C",2); TreeBuilder.Node node5 = new TreeBuilder.Node(5,1,"華西區域","D",2); TreeBuilder.Node node6 = new TreeBuilder.Node(6,1,"華中區域","E",2); TreeBuilder.Node node7 = new TreeBuilder.Node(7,6,"河南","豫",3); TreeBuilder.Node node8 = new TreeBuilder.Node(8,6,"湖北","鄂",3); TreeBuilder.Node node9 = new TreeBuilder.Node(9,6,"湖南","湘",3); TreeBuilder.Node node10 = new TreeBuilder.Node(10,6,"江西","贛",3); TreeBuilder.Node node11 = new TreeBuilder.Node(11,7,"鄭州","豫A",4); TreeBuilder.Node node12 = new TreeBuilder.Node(12,7,"開封","豫B",4); TreeBuilder.Node node13 = new TreeBuilder.Node(13,7,"洛陽","豫C",4); TreeBuilder.Node node14 = new TreeBuilder.Node(14,7,"南陽","豫R",4); TreeBuilder.Node node15 = new TreeBuilder.Node(15,11,"金水區","豫A-1",5); nodeList.add(node); nodeList.add(node1);nodeList.add(node2);nodeList.add(node3); nodeList.add(node4);nodeList.add(node5);nodeList.add(node6); nodeList.add(node7);nodeList.add(node8);nodeList.add(node9); nodeList.add(node10);nodeList.add(node11);nodeList.add(node12); nodeList.add(node13);nodeList.add(node14);nodeList.add(node15); return nodeList; }
然后調用new TreeBuilder().buildTree(nodeList)就可以返回json格式的字符串了：
package com.johanChan.WebSocket.controller; import com.alibaba.fastjson.JSON; import com.johanChan.WebSocket.utils.CommonUtils; import com.johanChan.WebSocket.utils.TreeBuilder; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.ResponseBody; import java.util.List; @Controller public class TreeController { List<TreeBuilder.Node> nodeList ; { nodeList = CommonUtils.buildNode(); } @ResponseBody @RequestMapping("/getTreeJson") public String getTreeJson() { // List<TreeBuilder.Node> nodeList = CommonUtils.buildNode(); String result = new TreeBuilder().buildTree(nodeList);
return result;
}
}
啟動項目，訪問/getTreeJson可以看到，頁面返回了json字符串：
整理后如下：
[
{
"children":[
{
"children":[
{
"code":"A",
"id":2,
"level":2,
"name":"華北區域",
"parentId":1
},
{
"code":"B",
"id":3,
"level":2,
"name":"華南區域",
"parentId":1
},
{
"code":"C",
"id":4,
"level":2,
"name":"華東區域",
"parentId":1
},
{
"code":"D",
"id":5,
"level":2,
"name":"華西區域",
"parentId":1
},
{
"children":[
{
"children":[
{
"children":[
{
"code":"豫A-1",
"id":15,
"level":5,
"name":"金水區",
"parentId":11
}
],
"code":"豫A",
"id":11,
"level":4,
"name":"鄭州",
"parentId":7
},
{
"code":"豫B",
"id":12,
"level":4,
"name":"開封",
"parentId":7
},
{
"code":"豫C",
"id":13,
"level":4,
"name":"洛陽",
"parentId":7
},
{
"code":"豫R",
"id":14,
"level":4,
"name":"南陽",
"parentId":7
}
],
"code":"豫",
"id":7,
"level":3,
"name":"河南",
"parentId":6
},
{
"code":"鄂",
"id":8,
"level":3,
"name":"湖北",
"parentId":6
},
{
"code":"湘",
"id":9,
"level":3,
"name":"湖南",
"parentId":6
},
{
"code":"贛",
"id":10,
"level":3,
"name":"江西",
"parentId":6
}
],
"code":"E",
"id":6,
"level":2,
"name":"華中區域",
"parentId":1
}
],
"code":"CHN",
"id":1,
"level":1,
"name":"中國",
"parentId":0
}
],
"code":"WORD",
"id":0,
"level":1,
"name":"地球",
"parentId":-1
}
]
第一種方法完成，下面是第二種實現，首先建立一個類：
package com.johanChan.WebSocket.utils;
import java.util.ArrayList;
import java.util.List;
public class Tree<T> {
/**
* 節點ID
*/
private Integer id;
/**
* 顯示節點文本
*/
private String text;
/**
* 父ID
*/
private Integer parentId;
private Integer level;
/**
* 節點的子節點
*/
// private List<Tree<T>> nodes = new ArrayList<Tree<T>>();
private List<Tree<T>> nodes = null;
public Tree() {}
public Tree(Integer id,Integer parentId,String text,Integer level){
super();
this.id = id;
this.text = text;
this.parentId = parentId;
this.level = level;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getText() {
return text;
}
public void setText(String text) {
this.text = text;
}
public Integer getParentId() {
return parentId;
}
public void setParentId(Integer parentId) {
this.parentId = parentId;
}
public Integer getLevel() {
return level;
}
public void setLevel(Integer level) {
this.level = level;
}
public List<Tree<T>> getNodes() {
if(nodes==null){
nodes = new ArrayList<Tree<T>>();
}
return nodes;
}
public void setNodes(List<Tree<T>> nodes) {
this.nodes = nodes;
}
}
然后對Tree進行排序：
package com.johanChan.WebSocket.utils;
import java.util.ArrayList; import java.util.List; public class BuildTree { public static <T> List<Tree<T>> build(List<Tree<T>> nodes) { if (nodes == null) { return null; } List<Tree<T>> topNodes = new ArrayList<>(); for (Tree<T> children : nodes) { String pid = children.getParentId(); if (pid.equals(children.getId() )) { topNodes.add(children); continue; } for (Tree<T> parent : nodes) { String id = parent.getId(); if (id != null && id.equals(pid)) { parent.getNodes().add(children); } } } return topNodes; } }
然后生成數據：
public static List<Tree<TreeBuilder.Node>> buildTree(){ List<Tree<TreeBuilder.Node>> treeList = new ArrayList<>(); Tree<TreeBuilder.Node> tree = new Tree<TreeBuilder.Node>(0,0,"地球",1); Tree tree1 = new Tree(1,0,"中國",1); Tree tree2 = new Tree(2,1,"華北區域",2); Tree tree3 = new Tree(3,1,"華南區域",2); Tree tree4 = new Tree(4,1,"華東區域",2); Tree tree5 = new Tree(5,1,"華西區域",2); Tree tree6 = new Tree(6,1,"華中區域",2); Tree tree7 = new Tree(7,6,"河南",3); Tree tree8 = new Tree(8,6,"湖北",3); Tree tree9 = new Tree(9,6,"湖南",3); Tree tree10 = new Tree(10,6,"江西",3); Tree tree11 = new Tree(11,7,"鄭州",4); Tree tree12 = new Tree(12,7,"開封",4); Tree tree13 = new Tree(13,7,"洛陽",4); Tree tree14 = new Tree(14,7,"南陽",4); Tree tree15 = new Tree(15,11,"金水區",5); treeList.add(tree); treeList.add(tree1);treeList.add(tree2);treeList.add(tree3); treeList.add(tree4);treeList.add(tree5);treeList.add(tree6); treeList.add(tree7);treeList.add(tree8);treeList.add(tree9); treeList.add(tree10);treeList.add(tree11);treeList.add(tree12); treeList.add(tree13);treeList.add(tree14);treeList.add(tree15); return treeList; }
調用方法：
package com.johanChan.WebSocket.controller; import com.alibaba.fastjson.JSON; import com.johanChan.WebSocket.utils.BuildTree; import com.johanChan.WebSocket.utils.CommonUtils; import com.johanChan.WebSocket.utils.Tree; import com.johanChan.WebSocket.utils.TreeBuilder; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.ResponseBody; import java.util.List; @Controller public class TreeController { List<TreeBuilder.Node> nodeList ; List<Tree<TreeBuilder.Node>> treeList; { nodeList = CommonUtils.buildNode(); treeList = CommonUtils.buildTree(); } @ResponseBody @RequestMapping("/getTreeJson") public String getTreeJson() { // List<TreeBuilder.Node> nodeList = CommonUtils.buildNode(); // String result = CommonUtils.buildTree(nodeList); List<Tree<TreeBuilder.Node>> resultList = BuildTree.build(treeList); String result = JSON.toJSONString(resultList); return result; } }
返回數據如下：
整理后：
[ { "id":0, "level":1, "nodes":[ { "id":1, "level":1, "nodes":[ { "id":2, "level":2, "nodes":[ ], "parentId":1, "text":"華北區域" }, { "id":3, "level":2, "nodes":[ ], "parentId":1, "text":"華南區域" }, { "id":4, "level":2, "nodes":[ ], "parentId":1, "text":"華東區域" }, { "id":5, "level":2, "nodes":[ ], "parentId":1, "text":"華西區域" }, { "id":6, "level":2, "nodes":[ { "id":7, "level":3, "nodes":[ { "id":11, "level":4, "nodes":[ { "id":15, "level":5, "nodes":[ ], "parentId":11, "text":"金水區" } ], "parentId":7, "text":"鄭州" }, { "id":12, "level":4, "nodes":[ ], "parentId":7, "text":"開封" }, { "id":13, "level":4, "nodes":[ ], "parentId":7, "text":"洛陽" }, { "id":14, "level":4, "nodes":[ ], "parentId":7, "text":"南陽" } ], "parentId":6, "text":"河南" }, { "id":8, "level":3, "nodes":[ ], "parentId":6, "text":"湖北" }, { "id":9, "level":3, "nodes":[ ], "parentId":6, "text":"湖南" }, { "id":10, "level":3, "nodes":[ ], "parentId":6, "text":"江西" } ], "parentId":1, "text":"華中區域" } ], "parentId":0, "text":"中國" } ], "parentId":0, "text":"地球" } ]
OK！以上兩種方法都比較有通用性，把自己的數據整理后調用就可以了。