集合转树json

Posted 2022-12-13 l_learning

在工作中会将菜单、部门数据转成树结构的json方便前端展示树

1、从数据库把具有父子(id, parent_id)结构的数据从数据库查出来

省略查询步骤，这里新建两个常见的父子结构的菜单和部门实体

public class Dept 

    private String deptId;

    private String deptName;

    private String parentDept;

    public Dept(String deptId, String deptName, String parentDept) 
        this.deptId = deptId;
        this.deptName = deptName;
        this.parentDept = parentDept;
    

    //......省略

public class Menu 

    private String id;

    private String name;

    private String icon;

    private String parentId;

    public Menu(String id, String name, String icon, String parentId) 
        this.id = id;
        this.name = name;
        this.icon = icon;
        this.parentId = parentId;
    
    
    //......省略

2、通过递归将集合数据转成树对象

import org.springframework.cglib.beans.BeanMap;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class DataTree 

    private String childrenName = "children";

    private String key = "id";

    private String parentKey = "parentId";

    public DataTree() 
    

    /**
     * 自定义树参数
     * @param childrenName  子节点名称
     * @param key   id字段名
     * @param parentKey 父ID字段名
     */
    public DataTree(String childrenName, String key, String parentKey) 
        this.childrenName = childrenName;
        this.key = key;
        this.parentKey = parentKey;
    

    private List<Map> parseMap(List data)
        List<Map> beanMaps = new ArrayList<Map>();
        if(data.isEmpty())
            return null;
        
        for (Object obj: data) 
            BeanMap beanMap = BeanMap.create(obj);
            Map map = new HashMap(beanMap);
            beanMaps.add(map);
        
        return beanMaps;
    

    /**
     * 根节点的为空生成树
     * @param data
     * @return
     */
    public List<Map> createTree(List data) 
        List<Map> treeMap = parseMap(data);
        List<Map> tree = new ArrayList<Map>();
        for (Map node : treeMap) 
            if (null == node.get(parentKey)) 
                List<Map> child = createTree((String) node.get(key), data);
                if(!child.isEmpty())
                    node.put(childrenName, child);
                
                tree.add(node);
            
        
        return tree;
    

    /**
     * 指定根节点开始生成树
     * @param parentNode    根节点
     * @param data
     * @return
     */
    public List<Map> createTree(String parentNode, List data) 
        List<Map> treeMap = parseMap(data);
        List<Map> tree = new ArrayList<Map>();
        for (Map node : treeMap) 
            if(parentNode.equals(node.get(parentKey)))
                List<Map> child = getChild(node, treeMap);
                if(!child.isEmpty())
                    node.put(childrenName, child);
                
                tree.add(node);
            
        
        return tree;
    

    /**
     * 获取子节点
     * @param parentNode 父节点
     * @param data  集合数据
     * @return
     */
    private List<Map> getChild(Map parentNode, List<Map> data) 
        List<Map> tree = new ArrayList<Map>();
        for (Map node : data) 
            //过滤根节点
            if(null != node.get(parentKey) &&
                    //过滤id等于parentId的异常数据
                    !node.get(key).equals(node.get(parentKey)) &&
                    //过滤循环节点
                    !(node.get(key).equals(parentNode.get(parentKey)) && node.get(parentKey).equals(parentNode.get(key))) &&
                    //符合条件的节点
                    parentNode.get(key).equals(node.get(parentKey)))
                List<Map> child = getChild(node, data);
                if(!child.isEmpty())
                    node.put(childrenName, child);
                
                tree.add(node);
            
        
        return tree;
    

3、测试

public class TreeTest 

    public static void main(String[] args) 
        List<Menu> menuTree = new ArrayList<Menu>();
        menuTree.add(new Menu("1", "首页", "no", null));
        menuTree.add(new Menu("2", "用户管理", "no", null));
        menuTree.add(new Menu("2-1", "修改头像", "no", "2"));
        menuTree.add(new Menu("2-2", "修改邮箱", "no", "2"));
        menuTree.add(new Menu("3", "系统管理", "no", null));
        menuTree.add(new Menu("3-1", "菜单", "no", "3"));
        menuTree.add(new Menu("3-2", "角色", "no", "3"));

        List<Dept> deptTree = new ArrayList<Dept>();
        deptTree.add(new Dept("1", "人事部", "0"));
        deptTree.add(new Dept("2", "信息部", "0"));
        deptTree.add(new Dept("2-1", "研发部", "2"));
        deptTree.add(new Dept("2-2", "测试部", "2"));
        deptTree.add(new Dept("2-3", "交付部", "2"));

        DataTree tree = new DataTree();
        List menuTreeDate = tree.createTree(menuTree);
        System.out.println(JSON.toJSONString(menuTreeDate));
        System.out.println(JSONArray.toJSONString(menuTreeDate));

        DataTree tree2 = new DataTree("child", "deptId", "parentDept");
        List deptTreeDate = tree2.createTree("0", deptTree);
        System.out.println(JSON.toJSONString(deptTreeDate));
        System.out.println(JSONArray.toJSON(deptTreeDate));