Java集合List转树结构工具类

此版本太累赘,请转到函数版:https://blog.csdn.net/wenxingchen/article/details/115749782?spm=1001.2014.3001.5501

业务场景:菜单树、组织架构树.....前端要求数据结构为树结构,而后端查出来的是一条一条的数据集,每次都要各种递归遍历很麻烦,特此写了一个工具类来解决.

三个注解:

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;/*** @author sunziwen* @since 2021-4-13 16:19:05*/
@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface TreeId {
}

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;/*** @author sunziwen* @since 2021-4-13 16:19:05*/
@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface TreeParentId {
}

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;/*** @author sunziwen* @since 2021-4-13 16:19:05*/
@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface TreeChildren {
}

一个工具类:

import cn.hutool.core.util.StrUtil;
import lombok.SneakyThrows;import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;/*** 树形工具类** @author sunziwen* @since 2021-4-13 16:19:05*/public class TreeUtil {/*** 找出顶层节点** @return data*/@SneakyThrowsprivate <T> List<T> treeOut(List<T> list) {//数据不能为空if (list == null || list.size() <= 0) {return list;}//获取泛型T的classClass<?> aClass = list.get(0).getClass();Field[] declaredFields = aClass.getDeclaredFields();//获取主键属性List<Field> idPropertyField = Arrays.stream(declaredFields).filter(x -> {TreeId annotation = x.getAnnotation(TreeId.class);return annotation != null;}).collect(Collectors.toList());if (idPropertyField.size() <= 0) {throw new RuntimeException("缺失@TreeId注解");}if (idPropertyField.size() > 1) {throw new RuntimeException("@TreeId注解只能存在一个");}//获取父节点属性List<Field> parentIdPropertyField = Arrays.stream(declaredFields).filter(x -> {TreeParentId annotation = x.getAnnotation(TreeParentId.class);return annotation != null;}).collect(Collectors.toList());if (parentIdPropertyField.size() <= 0) {throw new RuntimeException("缺失@ParentId注解");}if (parentIdPropertyField.size() > 1) {throw new RuntimeException("@ParentId注解只能存在一个");}/*主键的属性名*/String idPropertyName = idPropertyField.get(0).getName();/*主键的get方法*/Method getId = aClass.getMethod("get" + StrUtil.upperFirst(idPropertyName));/*父节点的属性名*/String parentIdPropertyName = parentIdPropertyField.get(0).getName();/*父节点的get方法*/Method getParentId = aClass.getMethod("get" + StrUtil.upperFirst(parentIdPropertyName));/*所有元素的Id*/List<Object> ids = list.stream().map(x -> {try {return getId.invoke(x);} catch (IllegalAccessException | InvocationTargetException e) {e.printStackTrace();}return null;}).collect(Collectors.toList());/*查出所有顶级节点*/List<T> topLevel = list.stream().filter(x -> {try {return !ids.contains(getParentId.invoke(x));} catch (IllegalAccessException | InvocationTargetException e) {e.printStackTrace();}return false;}).collect(Collectors.toList());return recursion(topLevel, list);}/*** 递归装载** @param superLevel 上级节点* @param list       数据集* @return*/@SneakyThrowsprivate <T> List<T> recursion(List<T> superLevel, List<T> list) {//获取泛型T的classClass<?> aClass = list.get(0).getClass();Field[] declaredFields = aClass.getDeclaredFields();//获取主键属性List<Field> idPropertyField = Arrays.stream(declaredFields).filter(x -> {TreeId annotation = x.getAnnotation(TreeId.class);return annotation != null;}).collect(Collectors.toList());if (idPropertyField.size() <= 0) {throw new RuntimeException("缺失@TreeId注解");}if (idPropertyField.size() > 1) {throw new RuntimeException("@TreeId注解只能存在一个");}//获取父节点属性List<Field> parentIdPropertyField = Arrays.stream(declaredFields).filter(x -> {TreeParentId annotation = x.getAnnotation(TreeParentId.class);return annotation != null;}).collect(Collectors.toList());if (parentIdPropertyField.size() <= 0) {throw new RuntimeException("缺失@ParentId注解");}if (parentIdPropertyField.size() > 1) {throw new RuntimeException("@ParentId注解只能存在一个");}//获取父节点属性List<Field> childrenPropertyField = Arrays.stream(declaredFields).filter(x -> {TreeChildren annotation = x.getAnnotation(TreeChildren.class);return annotation != null;}).collect(Collectors.toList());if (childrenPropertyField.size() <= 0) {throw new RuntimeException("缺失@TreeChildren注解");}if (childrenPropertyField.size() > 1) {throw new RuntimeException("@TreeChildren注解只能存在一个");}/*主键的属性名*/String idPropertyName = idPropertyField.get(0).getName();/*主键的get方法*/Method getId = aClass.getMethod("get" + StrUtil.upperFirst(idPropertyName));/*父节点的属性名*/String parentIdPropertyName = parentIdPropertyField.get(0).getName();/*父节点的get方法*/Method getParentId = aClass.getMethod("get" + StrUtil.upperFirst(parentIdPropertyName));/*子节点的属性名*/String childrenPropertyName = childrenPropertyField.get(0).getName();/*字节点的set方法*/Method setChildren = aClass.getMethod("set" + StrUtil.upperFirst(childrenPropertyName));for (T t : superLevel) {List<T> children = list.stream().filter(x -> {try {return getParentId.invoke(x).equals(getId.invoke(t));} catch (IllegalAccessException | InvocationTargetException e) {e.printStackTrace();}return false;}).collect(Collectors.toList());if (children.size() <= 0) {continue;}List<T> recursion = recursion(children, list);setChildren.invoke(t, recursion);}return superLevel;}
}

使用示例:


import lombok.Data;import java.util.List;@Data
public class My {@TreeId//在实体类的主键上打上该注解private String id;@TreeParentId//在实体类的父节点id上打上该注解private String parentId;private String name;@TreeChildren //在子集上打上该注解//@TableField(exist = false)//如果你用的是mybatis-plus则需要让框架忽略该字段private List<My> children;public My(String id, String parentId, String name) {this.id = id;this.parentId = parentId;this.name = name;}
}

    public static void main(String[] args) {ArrayList<My> mies = new ArrayList<>();mies.add(new My("1", "-1", "a"));mies.add(new My("2", "-1", "aa"));mies.add(new My("3", "1", "b"));mies.add(new My("4", "1", "c"));mies.add(new My("5", "3", "d"));mies.add(new My("6", "5", "e"));mies.add(new My("7", "6", "f"));mies.add(new My("8", "2", "g"));mies.add(new My("9", "8", "h"));mies.add(new My("10", "9", "i"));List<My> mies1 = TreeUtil.treeOut(mies);System.out.println(mies1);}

大功告成了,如果有问题请加博主V：sunziwen3366

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