Java实现树形结构的数据转Json格式

　　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。