java構(gòu)建樹形結(jié)構(gòu)的實現(xiàn)過程

更新時間：2025年11月10日 09:11:13 作者：xingweI2021

文章介紹了五種構(gòu)建樹形結(jié)構(gòu)的方式,包括定義實體類、利用Map集合、使用Stream流、基于Hutool以及MyBatis-Plus的@TableName屬性,最后,還提供了一個基于Java實現(xiàn)樹結(jié)構(gòu)模糊搜索功能的示例

構(gòu)建樹形結(jié)構(gòu)

廢話少說，直接上代碼

方式一

1、定義實體類

public class Category {

    private Long id;
    private String name;
    private Long parentId;
    private List<Category> children;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Long getParentId() {
        return parentId;
    }

    public void setParentId(Long parentId) {
        this.parentId = parentId;
    }

    public List<Category> getChildren() {
        return children;
    }

    public void setChildren(List<Category> children) {
        this.children = children;
    }

    public Category(Long id, String name, Long parentId) {
        this.id = id;
        this.name = name;
        this.parentId = parentId;
    }
}

工具類

private static List<Category> categories = new ArrayList<>();

static {
    // 綁定初始化一個Category的數(shù)據(jù)
    categories.add(new Category(1L, "一級分類-1", null));
    categories.add(new Category(2L, "一級分類-1-1", 1L));
    categories.add(new Category(3L, "一級分類-1-2", 1L));
    categories.add(new Category(30L, "一級分類-1-2-1", 3L));
    categories.add(new Category(4L, "一級分類-2", null));
    categories.add(new Category(5L, "一級分類-2-1", 4L));
    categories.add(new Category(6L, "一級分類-3", null));
    categories.add(new Category(7L, "一級分類-3-1", 6L));
    // 子節(jié)點
}

public static void main(String[] args) {
    String treeJson = JSONUtil.toJsonPrettyStr(parentList01());
    System.out.println(treeJson);
}

private static List<Category> parentList01(){
    List<Category> parentList = categories.stream().filter(category -> category.getParentId() == null).collect(Collectors.toList());
    for (Category category : parentList) {
        category.setChildren(buildChildren(category.getId(),categories));
    }
    return parentList;
}

private static List<Category> buildChildren(Long id, List<Category> categories) {
    List<Category> children = new ArrayList<>();
    for (Category category : categories) {
        if (category.getParentId() == null){
            continue;
        }
        if (category.getParentId().equals(id)){
            children.add(category);
        }
    }
    for (Category child : children) {
        child.setChildren(buildChildren(child.getId(),categories));
    }
    return children;
}

方式二

利用Map集合

@Override
public Result currentLeftMenu() {
    // 獲取認證主體
    Subject subject = SecurityUtils.getSubject();
    ActiveUser activeUser = (ActiveUser) subject.getPrincipal();
    Integer userId = activeUser.getSysUser().getId();
    // 根據(jù)用戶ID 和 菜單權(quán)限查詢 權(quán)限
    List<SysPermissionVO> sysPermissionVOS = sysPermissionMapper.selectUserPermission(userId, Constant.PERMISSION_TYPE_MENU);
    // 菜單容器
    Map<Integer, SysPermissionVO> menu = new HashMap<>();

    for (SysPermissionVO sysPermissionVO : sysPermissionVOS) {
        // 獲取菜單中的父ID
        Integer parentId = sysPermissionVO.getParentId();
        // 判斷父ID是否是一級菜單
        if (parentId.equals(Constant.MENU_LV1)) {
            sysPermissionVO.setChildren(new ArrayList<SysPermissionVO>());
            // key 菜單的ID value
            menu.put(sysPermissionVO.getId(), sysPermissionVO);
        }
    }
    // 給1一級菜單賦二級菜單
    for (SysPermissionVO sysPermissionVO : sysPermissionVOS) {
        Integer parentId = sysPermissionVO.getParentId();
        if (menu.containsKey(parentId)) {
            SysPermissionVO sysPermissionVO1 = menu.get(parentId);
            sysPermissionVO1.getChildren().add(sysPermissionVO);
        }
    }
    Collection<SysPermissionVO> values = menu.values();
    // 返回給controller
    return new Result(values);
}

方式三：stream流方式

public List<CategoryEntity> listWithTree() {
    //1、查出所有分類
    List<CategoryEntity> entities = baseMapper.selectList(null);

    //2、組裝成父子的樹形結(jié)構(gòu)
    //2.1）、找到所有的一級分類，給children設(shè)置子分類
    return entities.stream()
        // 過濾找出一級分類
        .filter(categoryEntity -> categoryEntity.getParentCid() == 0)
        // 處理，給一級菜單遞歸設(shè)置子菜單
        .peek(menu -> menu.setChildren(getChildless(menu, entities)))
        // 按sort屬性排序
        .sorted(Comparator.comparingInt(menu -> (menu.getSort() == null ? 0 : menu.getSort())))
        .collect(Collectors.toList());
}

/**
 * 遞歸查找所有菜單的子菜單
 */
private List<CategoryEntity> getChildless(CategoryEntity root, List<CategoryEntity> all) {
    return all.stream()
        .filter(categoryEntity -> categoryEntity.getParentCid().equals(root.getCatId()))
        .peek(categoryEntity -> {
            // 找到子菜單
            categoryEntity.setChildren(getChildless(categoryEntity, all));
        })
        .sorted(Comparator.comparingInt(menu -> (menu.getSort() == null ? 0 : menu.getSort())))
        .collect(Collectors.toList());
}

另一個

public List<CategoryEntity> listWithLambda() {

    List<CategoryEntity> categorys = baseMapper.selectList(Wrappers.<CategoryEntity>lambdaQuery().orderByDesc(CategoryEntity::getCatId))
    List<CategoryEntity> entities = new ArrayList<>(categorys);
    Map<Long, List<CategoryEntity>> longListNavigableMap = entities.stream().collect(Collectors.groupingBy(CategoryEntity::getParentCid));

    List<CategoryEntity> res = entities.stream().peek(entity -> {
        if (longListNavigableMap.containsKey(entity.getCatId())) {
            entity.setChildren(longListNavigableMap.get(entity.getCatId()));
        }
    }).filter(entity -> entity.getCatLevel() == 1).sorted(Comparator.comparingInt(menu -> (menu.getSort() == null ? 0 : menu.getSort()))).collect(Collectors.toList());

    return res;
}

方式四：基于Hutool進行構(gòu)建

導(dǎo)入hutool的依賴，請參考hutool官網(wǎng)

實體類

@Data
@TableName("pms_category")
@AllArgsConstructor
public class CategoryEntity implements Serializable {
	private static final long serialVersionUID = 1L;

	/**
	 * 分類id
	 */
	@TableId
	private Long catId;
	/**
	 * 分類名稱
	 */
	private String name;
	/**
	 * 父分類id
	 */
	private Long parentCid;
	/**
	 * 層級
	 */
	private Integer catLevel;
	/**
	 * 是否顯示[0-不顯示，1顯示]
	 */
	@TableLogic(value = "1",delval = "0")
	private Integer showStatus;
	/**
	 * 排序
	 */
	private Integer sort;
	/**
	 * 圖標(biāo)地址
	 */
	private String icon;
	/**
	 * 計量單位
	 */
	private String productUnit;
	/**
	 * 商品數(shù)量
	 */
	private Integer productCount;

	/**
	 * 所有子分類
	 */
	@JsonInclude(JsonInclude.Include.NON_EMPTY)
	@TableField(exist = false)
	private List<CategoryEntity> children;

}

service

public class TreeUtils{
    public List<Tree<Long>> listWithTree() {
        ArrayList<CategoryEntity> dataList = Lists.newArrayList();
        dataList.add(new CategoryEntity(1L,"電子產(chǎn)品",0L,1,1,0,"/images/electronics.png","件",50,null));
        dataList.add(new CategoryEntity(2L,"手機通訊",1L,2,1,0,"/images/electronics.png","件",150,null));
        dataList.add(new CategoryEntity(3L,"家用電器",1L,2,1,0,"/images/electronics.png","件",250,null));
        List<CategoryEntity> entities = dataList;
        if (!CollectionUtil.isEmpty(entities)) {
            List<TreeNode<Long>> list = entities.
                    stream().
                    map(CategoryServiceImpl::getLongTreeNode).
                    collect(Collectors.toList());
            return TreeUtil.build(list, 0L);
        }
        return Collections.emptyList();
    }

    private static TreeNode<Long> getLongTreeNode(CategoryEntity item) {
	    TreeNode<Long> treeNode = new TreeNode<>();
	    treeNode.setId(item.getCatId());
	    treeNode.setParentId(item.getParentCid());
	    treeNode.setName(item.getName());
	    treeNode.setWeight(item.getSort());
	    Map<String, Object> extra = new HashMap<>();
	    extra.put("showStatus", item.getShowStatus());
	    extra.put("catLevel", item.getCatLevel());
	    extra.put("icon", item.getIcon());
	    extra.put("productUnit", item.getProductUnit());
	    extra.put("productCount", item.getProductCount());
	    treeNode.setExtra(extra);
	    return treeNode;
	}
}

測試

public static void main(String[] args) {
    List<Tree<Long>> trees = listWithTree1();
    System.out.println(JSONUtil.toJsonPrettyStr(trees));
}

方式五

基于mybatisplus的@TableName里面的resultMap屬性，當(dāng)發(fā)生查詢時，會根據(jù)配置的xml查詢SQL進行查詢

mapper.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.xw.mapper.FuncMapper">
    <resultMap id="thCloudFuncMap" type="com.xw.entity.Func">
        <id column="id" property="id"/>
        <result column="creator" property="creator"/>
        <result column="creator_name" property="creatorName"/>
        <result column="updater" property="updater"/>
        <result column="updater_name" property="updaterName"/>
        <result column="code" property="code"/>
        <result column="name" property="name"/>
        <result column="icon" property="icon"/>
        <result column="note" property="note"/>
        <result column="parent_id" property="parentId"/>
        <result column="sort" property="sort"/>
        <result column="component_name" property="componentName"/>
        <result column="type" property="type"/>
        <collection column="id" property="children" select="findByParentId" ofType="com.telehot.tpf.dev.rolemenu.entity.ThCloudFunc">
        </collection>
    </resultMap>


    <select id="findByParentId" resultMap="funcMap">
        SELECT * FROM func WHERE parent_id = #{parentId}
    </select>


    <select id="findAll" resultMap="funcMap">
        SELECT * FROM func where is_disabled = 0
    </select>
</mapper>

實體類

@TableName(value = "func", resultMap = "funcMap")
public class Func extends Entity {


    /**
     * 編碼
     */
    private String code;

    /**
     * 菜單名稱
     */
    private String name;

    /**
     * 圖標(biāo)
     */
    private String icon;

    /**
     * 圖標(biāo)
     */
    private String selectIcon;

    /**
     * 說明
     */

    private String note;

    /**
     * 父類ID
     */
    private Long parentId;

    /**
     * 排序
     */
    private Integer sort;

    /**
     * 類型
     */
    private Integer type;

    /**
     * 路徑
     */
    private String path;

    /**
     * 應(yīng)用id
     */
    private String appId;

    /***
     * 組件名
     */
    private String componentName;

    /**
     * 層級
     */
    private Integer tier;


    @TableField(exist = false)
    private List<Func> children;

}