java通用的树结构生成工具

根据反射获取相关字段进行比对以生成树，代码比较简单，就不做过多说明了。

package xyz.iotcode.xs.starter.common.util;

import cn.hutool.core.collection.CollUtil;
import com.alibaba.fastjson.JSON;
import lombok.Data;

import java.lang.reflect.Field;
import java.util.*;

/**
 * @author xieshuang
 * @date 2020-08-13 15:14
 */
public class TreeUtils<T> {
     

    public List<T> longTree(List<T> list) throws IllegalAccessException {
     
        return tree(list, "id", "pid", "child", 0L);
    }

    public List<T> intTree(List<T> list) throws IllegalAccessException {
     
        return tree(list, "id", "pid", "child", 0);
    }

    public List<T> stringTree(List<T> list) throws IllegalAccessException {
     
        return tree(list, "id", "pid", "child", "0");
    }

    public List<T> tree(List<T> list, String idName, String pidName, String childName, Object topValue) throws IllegalAccessException {
     
        if (CollUtil.isEmpty(list)){
     
            return Collections.emptyList();
        }
        Class<?> aClass = list.get(0).getClass();
        Map<String, Field> vFieldMap = getAllFieldMap(aClass);
        Field idField = vFieldMap.get(idName);
        if (idField == null){
     
            throw new IllegalArgumentException("找不到 " + idName + "属性");
        }
        Field pidField = vFieldMap.get(pidName);
        if (pidField == null){
     
            throw new IllegalArgumentException("找不到 " + pidName + "属性");
        }
        Field childField = vFieldMap.get(childName);
        if (childField == null){
     
            throw new IllegalArgumentException("找不到 " + childName + "属性");
        }
        Map<Object, List<T>> map = new HashMap<>();
        for (T t : list) {
     
            Object value = pidField.get(t);
            List<T> objects = map.get(value);
            if (CollUtil.isEmpty(objects)){
     
                objects = new ArrayList<>();
                map.put(value, objects);
            }
            objects.add(t);
        }
        List<T> objectList = new ArrayList<>();
        List<T> topList = map.get(topValue);
        if (CollUtil.isNotEmpty(topList)){
     
            for (T o : topList) {
     
                objectList.add(addChildNode(o, map, idField, childField));
            }
        }
        return objectList;
    }

    private T addChildNode(T treeNode, Map<Object, List<T>> map, Field idField, Field childField) throws IllegalAccessException {
     
        List<T> objectList = map.get(idField.get(treeNode));
        if (CollUtil.isNotEmpty(objectList)){
     
            List<T> treeNodeList = new ArrayList<>();
            for (T t : objectList) {
     
                treeNodeList.add(addChildNode(t, map, idField, childField));
            }
            childField.set(treeNode, treeNodeList);
        }
        return treeNode;
    }

    private Map<String, Field> getAllFieldMap(Class<?> cls){
     
        Field[] vFields = getAllFields(cls);
        Map<String, Field> fieldMap = new HashMap<>(vFields.length);
        for (Field field : vFields) {
     
            field.setAccessible(true);
            fieldMap.put(field.getName(), field);
        }
        return fieldMap;
    }

    private static Field[] getAllFields(final Class<?> cls) {
     
        final List<Field> allFieldsList = getAllFieldsList(cls);
        return allFieldsList.toArray(new Field[0]);
    }

    private static List<Field> getAllFieldsList(final Class<?> cls) {
     
        if (cls==null){
     
            throw new IllegalArgumentException("The class must not be null");
        }
        final List<Field> allFields = new ArrayList<>();
        Class<?> currentClass = cls;
        while (currentClass != null) {
     
            final Field[] declaredFields = currentClass.getDeclaredFields();
            allFields.addAll(Arrays.asList(declaredFields));
            currentClass = currentClass.getSuperclass();
        }
        return allFields;
    }

    @Data
    static class MyTree{
     
        private Integer id;
        private String name;
        private Integer pid;
        private List<MyTree> child;
    }

    public static void main(String[] args) throws IllegalAccessException {
     
        List<MyTree> trees = new ArrayList<>();
        for (int i = 1; i < 10; i++) {
     
            MyTree myTree = new MyTree();
            myTree.setName("顶级"+i);
            myTree.setId(i);
            myTree.setPid(0);
            trees.add(myTree);
            for (int j = 0; j <10 ; j++) {
     
                MyTree myTree1 = new MyTree();
                myTree1.setName("子级"+j);
                myTree1.setId(j+(i*100));
                myTree1.setPid(i);
                trees.add(myTree1);
                for (int k = 0; k <10 ; k++) {
     
                    MyTree myTree2 = new MyTree();
                    myTree2.setName("子级"+j);
                    myTree2.setId(k+(j*100)+(i*10000));
                    myTree2.setPid(j+(i*100));
                    trees.add(myTree2);
                }
            }
        }
        System.out.println(trees.size());
        System.out.println("开始生成树");
        long l = System.currentTimeMillis();
        Collection<MyTree> tree = new TreeUtils<MyTree>().intTree(trees);
        long l2 = System.currentTimeMillis();
        System.out.println("生成树耗时：" + (l2 - l));
        System.out.println(JSON.toJSONString(tree));
    }
}