Java & JavaScript 递归构建树状图（根据parentId）

Posted 2021-07-09 Z && Y

1. Java & javascript 递归构建树状图（根据parentId）

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类似于实现这样的效果

实现思路：

1. 第一步：找到所有根节点（parentId == null）
2. 第二步：遍历跟结点，递归生成根节点的子树

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1.1 JavaScript 实现

export class TaskManageModal {
  taskId: any = ''; // 任务id
  parentId: any = ''; // 父级任务id
  children: Array<TaskManageModal> = [];// 是否含有子列表
}

taskInfoList: Array<TaskManageModal> = 待处理的数据;

//建立树形结构
buildTree(): Array<TaskManageModal> {
  let treeList: Array<TaskManageModal> = [];
  let rootNodes = this.getRootNode();
  for (let j = 0; j < rootNodes.length; j++) {
    treeList.push(this.buildChildTree(rootNodes[j]));
  }
  return treeList;
}
// 获取根节点(一级树)
getRootNode(): Array<TaskManageModal> {
  let rootList: Array<TaskManageModal> = [];
  for (let j = 0; j < this.taskInfoList.length; j++) {
    if (this.taskInfoList[j].parentId == undefined) {
      rootList.push(this.taskInfoList[j]);
    }
  }
  return rootList;
}
// 递归，建立子树形结构
buildChildTree(task: TaskManageModal): TaskManageModal {
  let childList: Array<TaskManageModal> = [];
  for (let j = 0; j < this.taskInfoList.length; j++) {
    if (this.taskInfoList[j].parentId == task.taskId) {
      childList.push(this.buildChildTree(this.taskInfoList[j]));
    }
  }
  task.children = childList;
  return task;
}

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1.2 Java代码实现

我用到的依赖

pom.xml

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.60</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.20</version>
            <scope>provided</scope>
        </dependency>

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1.2.1 实体类Menu

Menu.java

import lombok.Data;

import java.util.List;

@Data
public class Menu {
    private String id;
    private String parentId;
    private String text;
    private List<Menu> children;

    public Menu(String id, String parentId, String text) {
        this.id = id;
        this.parentId = parentId;
        this.text = text;
    }
}

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1.2.2 生成树形结构的类

MenuTree.java

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

public class MenuTree {
    private List<Menu> menuList = new ArrayList<Menu>();

    public MenuTree(List<Menu> menuList) {
        this.menuList = menuList;
    }

    //建立树形结构
    public List<Menu> builTree() {
        List<Menu> treeMenus = new ArrayList<Menu>();
        for (Menu menuNode : getRootNode()) {
            menuNode = buildChilTree(menuNode);
            treeMenus.add(menuNode);
        }
        return treeMenus;
    }

    //递归，建立子树形结构
    private Menu buildChilTree(Menu pNode) {
        List<Menu> chilMenus = new ArrayList<Menu>();
        for (Menu menuNode : menuList) {
            if (menuNode.getParentId().equals(pNode.getId())) {
                chilMenus.add(buildChilTree(menuNode));
            }
        }
        pNode.setChildren(chilMenus);
        return pNode;
    }

    //获取根节点
    private List<Menu> getRootNode() {
        List<Menu> rootMenuLists = new ArrayList<Menu>();
        for (Menu menuNode : menuList) {
            if (menuNode.getParentId().equals("0")) {
                rootMenuLists.add(menuNode);
            }
        }
        return rootMenuLists;
    }
}

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1.2.3 测试类

Test.java

import com.alibaba.fastjson.JSON;

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

public class Test {
    public static void main(String[] args) {
        List<Menu> menuList = new ArrayList<Menu>();
        /*插入一些数据*/
        menuList.add(new Menu("GN001D000", "0", "系统管理"));
        menuList.add(new Menu("GN001D100", "GN001D000", "权限管理"));
        menuList.add(new Menu("GN001D110", "GN001D100", "密码修改"));
        menuList.add(new Menu("GN001D120", "GN001D100", "新加用户"));
        menuList.add(new Menu("GN001D200", "GN001D000", "系统监控"));
        menuList.add(new Menu("GN001D210", "GN001D200", "在线用户"));
        menuList.add(new Menu("GN002D000", "0", "订阅区"));
        menuList.add(new Menu("GN003D000", "0", "未知领域"));
        /*让我们创建树*/
        MenuTree menuTree = new MenuTree(menuList);
        menuList = menuTree.builTree();
        /*转为json看看效果*/
        String jsonOutput = JSON.toJSONString(menuList);
        System.out.println(jsonOutput);
    }
}

运行结果：

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