树数据list封装到实体工具类

package com.cfzq.lz.msg.util; import java.lang.reflect.InvocationTargetException; import java.util.ArrayList; import java.util.List; /** * Created By JGMa on 2020-07-02 */ public class TreeUtils { private static final String ROOT_ID = "0"; private static final String GET = "get"; private static final String SET = "set"; /** * 私有构造器 */ private TreeUtils() { throw new IllegalStateException("Utility class"); } /** * 使用递归方法建树 * (如果项目中的各个表的id、父id、封装子对象的list名称均是固定，则可以再次简化，将反射获取属性的过程直接写 * 死，这样调用时只需传list即可) * @param list 需要转化树形的list * @param idName 实体类中id的属性名(首字母需要大写,例如属性为id,则传Id) * @param parentIdName 实体类中父id的属性名(首字母需要大写,例如属性为parentId,则传ParentId) * @param childrenName 实体类中封装树形的子list方法名(首字母需要大写,例如属性为list,则传List) * @return 树形list */ public static <T> List<T> buildByRecursive(List<T> list, String idName, String parentIdName, String childrenName) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException { List<T> result = new ArrayList<>(); //遍历封装pid=0的 for (T t : list) { //根据反射，获取父id的值 String pId = reflect(t.getClass(), GET + parentIdName, t).toString(); //如果pd=0，即是首层 if (ROOT_ID.equals(pId)) { //递归查询并封装子对象 result.add(findChildren(t, list, idName, parentIdName, childrenName)); } } return result; } /** * 递归查找子节点 * * @param idName 实体类中id的属性名(首字母需要大写) * @param parentIdName 实体类中父id的属性名(首字母需要大写) * @param bean * @param beans * @return */ public static <T> T findChildren(T bean, List<T> beans, String idName, String parentIdName, String childrenName) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException { //获取bean的id, bean.getId() String id = bean.getClass().getMethod(GET + idName).invoke(bean).toString(); //获取bean用来封装子对象的list, bean.getList() List<T> children = (List) reflect(bean.getClass(), GET + childrenName, bean); //递归遍历 for (T it : beans) { //根据反射，获取it的pId的值 it.getParentId() String parentId = it.getClass().getMethod(GET + parentIdName).invoke(it).toString(); //如果是其子对象 if (id.equals(parentId)) { //如果封装子对象的list为空，则创建 if (children == null) { bean.getClass().getMethod(SET + childrenName, List.class).invoke(bean, new ArrayList<>()); } //重新获取子对象的list children = (List) reflect(bean.getClass(), GET + childrenName, bean); //继续递归遍历 children.add(findChildren(it, beans, idName, parentIdName, childrenName)); } } return bean; } /** * 根据反射获取属性值 * * @param clazz 实体类名 * @param methodName 方法名 * @param t 对象 * @param <T> 对象类 * @return */ public static <T> Object reflect(Class clazz, String methodName, T t) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException { return clazz.getMethod(methodName).invoke(t); } }

用法

List<User> msgTypeVos = TreeUtils.buildByRecursive(list, "Id", "Pid", "ChildrenList");

实体

public class User(){ private String id; private String pid; private List<User> childrenList; get... set... }