在项目中难免会用到树形结构，毕竟这是一种常用的组织架构。楼主这里整理了两个实现的版本，可以直接拿来使用，非常方便。
楼主没有单独建项目，直接在以前的一个Demo上实现的。第一种，看下面代码：
package com.johanChan.WebSocket.utils;
import com.alibaba.fastjson.JSON; import java.util.ArrayList; import java.util.List; //图层结构 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; } // 构建JSON树形结构 public String buildJSONTree() { List<Node> nodeTree = buildTree(); String jsonStr = JSON.toJSONString(nodeTree); return jsonStr; } // 构建树形结构 public List<Node> buildTree() { List<Node> treeNodes = new ArrayList<>(); List<Node> rootNodes = getRootNodes(); for (Node rootNode : rootNodes) { buildChildNodes(rootNode); treeNodes.add(rootNode); } return treeNodes; } // 递归子节点 public void buildChildNodes(Node node) { List<Node> children = getChildNodes(node); if (!children.isEmpty()) { for (Node child : children) { buildChildNodes(child); } node.setChildren(children); } } // 获取父节点下所有的子节点 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; } // 判断是否为根节点 public boolean rootNode(Node node) { boolean isRootNode = true; for (Node n : nodes) { if (node.getParentId().equals(n.getId())) { isRootNode = false; break; } } return isRootNode; } // 获取集合中所有的根节点 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; } } }
看起来很长对吗？没关系，直接copy一下就可以使用。首先生成一个树形结构的数据：
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,"中国","CHN",1); TreeBuilder.Node node2 = new TreeBuilder.Node(2,1,"华北区域","A",2); TreeBuilder.Node node3 = new TreeBuilder.Node(3,1,"华南区域","B",2); TreeBuilder.Node node4 = new TreeBuilder.Node(4,1,"华东区域","C",2); TreeBuilder.Node node5 = new TreeBuilder.Node(5,1,"华西区域","D",2); TreeBuilder.Node node6 = new TreeBuilder.Node(6,1,"华中区域","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","赣",3); TreeBuilder.Node node11 = new TreeBuilder.Node(11,7,"郑州","豫A",4); TreeBuilder.Node node12 = new TreeBuilder.Node(12,7,"开封","豫B",4); TreeBuilder.Node node13 = new TreeBuilder.Node(13,7,"洛阳","豫C",4); TreeBuilder.Node node14 = new TreeBuilder.Node(14,7,"南阳","豫R",4); TreeBuilder.Node node15 = new TreeBuilder.Node(15,11,"金水区","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; }
然后调用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;
}
}
启动项目，访问/getTreeJson可以看到，页面返回了json字符串：
整理后如下：
[
{
"children":[
{
"children":[
{
"code":"A",
"id":2,
"level":2,
"name":"华北区域",
"parentId":1
},
{
"code":"B",
"id":3,
"level":2,
"name":"华南区域",
"parentId":1
},
{
"code":"C",
"id":4,
"level":2,
"name":"华东区域",
"parentId":1
},
{
"code":"D",
"id":5,
"level":2,
"name":"华西区域",
"parentId":1
},
{
"children":[
{
"children":[
{
"children":[
{
"code":"豫A-1",
"id":15,
"level":5,
"name":"金水区",
"parentId":11
}
],
"code":"豫A",
"id":11,
"level":4,
"name":"郑州",
"parentId":7
},
{
"code":"豫B",
"id":12,
"level":4,
"name":"开封",
"parentId":7
},
{
"code":"豫C",
"id":13,
"level":4,
"name":"洛阳",
"parentId":7
},
{
"code":"豫R",
"id":14,
"level":4,
"name":"南阳",
"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":"赣",
"id":10,
"level":3,
"name":"江西",
"parentId":6
}
],
"code":"E",
"id":6,
"level":2,
"name":"华中区域",
"parentId":1
}
],
"code":"CHN",
"id":1,
"level":1,
"name":"中国",
"parentId":0
}
],
"code":"WORD",
"id":0,
"level":1,
"name":"地球",
"parentId":-1
}
]
第一种方法完成，下面是第二种实现，首先建立一个类：
package com.johanChan.WebSocket.utils;
import java.util.ArrayList;
import java.util.List;
public class Tree<T> {
/**
* 节点ID
*/
private Integer id;
/**
* 显示节点文本
*/
private String text;
/**
* 父ID
*/
private Integer parentId;
private Integer level;
/**
* 节点的子节点
*/
// 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;
}
}
然后对Tree进行排序：
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; } }
然后生成数据：
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,"中国",1); Tree tree2 = new Tree(2,1,"华北区域",2); Tree tree3 = new Tree(3,1,"华南区域",2); Tree tree4 = new Tree(4,1,"华东区域",2); Tree tree5 = new Tree(5,1,"华西区域",2); Tree tree6 = new Tree(6,1,"华中区域",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,"郑州",4); Tree tree12 = new Tree(12,7,"开封",4); Tree tree13 = new Tree(13,7,"洛阳",4); Tree tree14 = new Tree(14,7,"南阳",4); Tree tree15 = new Tree(15,11,"金水区",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; }
调用方法：
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; } }
返回数据如下：
整理后：
[ { "id":0, "level":1, "nodes":[ { "id":1, "level":1, "nodes":[ { "id":2, "level":2, "nodes":[ ], "parentId":1, "text":"华北区域" }, { "id":3, "level":2, "nodes":[ ], "parentId":1, "text":"华南区域" }, { "id":4, "level":2, "nodes":[ ], "parentId":1, "text":"华东区域" }, { "id":5, "level":2, "nodes":[ ], "parentId":1, "text":"华西区域" }, { "id":6, "level":2, "nodes":[ { "id":7, "level":3, "nodes":[ { "id":11, "level":4, "nodes":[ { "id":15, "level":5, "nodes":[ ], "parentId":11, "text":"金水区" } ], "parentId":7, "text":"郑州" }, { "id":12, "level":4, "nodes":[ ], "parentId":7, "text":"开封" }, { "id":13, "level":4, "nodes":[ ], "parentId":7, "text":"洛阳" }, { "id":14, "level":4, "nodes":[ ], "parentId":7, "text":"南阳" } ], "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":"华中区域" } ], "parentId":0, "text":"中国" } ], "parentId":0, "text":"地球" } ]
OK！以上两种方法都比较有通用性，把自己的数据整理后调用就可以了。