设计及封装无限层级的树状结构

需求：电商项目中，在商品的品类管理模块，会涉及到递归调用出该节点的所有子节点的操作。

数据表设计：

category表.jpg

Category:

public class Category {
    private Integer id;

    private Integer parentId;

    private String name;

    private Boolean status;

    private Integer sortOrder;

    private Date createTime;

    private Date updateTime;

    @Override
    public boolean equals(Object o){
        if(this == o){
            return true;
        }
        if(o == null || getClass() != o.getClass()){
            return false;
        }
        Category category = (Category) o;
        return !(id!=null?!id.equals(category.id):category.id!=null);
    }

    @Override
    public int hashCode(){
        return id!=null?id.hashCode():0;
    }
}

Controller:

/**
 * 根据传的categoryId获取当前categoryId下边节点的category信息（平级，无递归）
 * @param session
 * @param categoryId
 * @return
 */
@RequestMapping("get_category.do")
@ResponseBody
public ServerResponse getChildrenParallelCategory(HttpSession session,
                                                  @RequestParam(value = "categoryId",defaultValue = "0") Integer categoryId){
    User user = (User)session.getAttribute(Const.CURRENT_USER);
    if(user == null){
        return ServerResponse.createByErrorCodeMessage(ResponseCode.NEED_LOGIN.getCode(),"用户未登录，请先登录");
    }
    if(iUserService.checkAdminRole(user).isSuccess()){
        //查询子节点的category信息，并且不递归，保持平级
        return iCategoryService.getChildrenParallelCategory(categoryId);
    }else {
        return ServerResponse.createByErrorMessage("无权限操作，需要管理员权限");
    }
}


/**
 * 获取当前的categoryId并且递归查询它的子节点的categoryId
 * @param session
 * @param categoryId
 * @return
 */
@RequestMapping("get_deep_category.do")
@ResponseBody
public ServerResponse getCategoryAndDeepChildrenCategory(HttpSession session,
                                                  @RequestParam(value = "categoryId",defaultValue = "0") Integer categoryId){

    User user = (User)session.getAttribute(Const.CURRENT_USER);
    if(user == null){
        return ServerResponse.createByErrorCodeMessage(ResponseCode.NEED_LOGIN.getCode(),"用户未登录，请先登录");
    }
    if(iUserService.checkAdminRole(user).isSuccess()){
        //查询当前节点的id和递归子节点的id
        return iCategoryService.selectCategoryAndChildrenById(categoryId);
    }else {
        return ServerResponse.createByErrorMessage("无权限操作，需要管理员权限");
    }
}

ServiceImpl:

@Override
public ServerResponse<List<Category>> getChildrenParallelCategory(Integer categoryId){
    List<Category> categoryList = categoryMapper.selectCategoryChildrenParentId(categoryId);
    if(CollectionUtils.isEmpty(categoryList)){
        logger.info("未找到当前分类的子分类");
    }
    return ServerResponse.createBySuccess(categoryList);
}

/**
 * 递归查询本节点的id及其子孙节点的id：获取当前categoryId下的子节点，还要继续查找子节点是否还有子节点，及所有子孙节点
 * 0-->10-->100
 * 如果传0，会返回10和100
 * 如果传10，会返回100
 * @param categoryId
 * @return
 */
@Override
public ServerResponse<List<Integer>> selectCategoryAndChildrenById(Integer categoryId){
    HashSet<Category> categorySet = Sets.newHashSet();
    findChildCategory(categorySet,categoryId);

    List<Integer> categoryIdList = Lists.newArrayList();
    if(categoryId!=null){
        for(Category categoryItem : categorySet){
            categoryIdList.add(categoryItem.getId());
        }
    }
    return ServerResponse.createBySuccess(categoryIdList);
}

递归算法：

/**
 * 为了使使用set集合不重复，需要重写hashcode和equals方法
 * 递归算法：算出子节点
 * @param categorySet
 * @param categoryId
 * @return
 */
private Set<Category> findChildCategory(Set<Category> categorySet,Integer categoryId){
    Category category = categoryMapper.selectByPrimaryKey(categoryId);
    if(category!=null){
        categorySet.add(category);
    }
    //查找子节点，递归算法一定要有一个退出的条件
    List<Category> categoryList = categoryMapper.selectCategoryChildrenParentId(categoryId);
    for(Category categoryItem:categoryList){
        findChildCategory(categorySet,categoryItem.getId());
    }
    return categorySet;
}

mapper：

public interface CategoryMapper {
    int deleteByPrimaryKey(Integer id);

    int insert(Category record);

    int insertSelective(Category record);

    Category selectByPrimaryKey(Integer id);

    int updateByPrimaryKeySelective(Category record);

    int updateByPrimaryKey(Category record);

    /**
     * 根据categoryId获取孩子节点的category信息
     * @param parentId
     * @return
     */
    List<Category> selectCategoryChildrenParentId(Integer parentId);
}

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.hcxmall.dao.CategoryMapper" >
  <resultMap id="BaseResultMap" type="com.hcxmall.pojo.Category" >
    <constructor>
      <idArg column="id" jdbcType="INTEGER" javaType="java.lang.Integer" />
      <arg column="parent_id" jdbcType="INTEGER" javaType="java.lang.Integer" />
      <arg column="name" jdbcType="VARCHAR" javaType="java.lang.String" />
      <arg column="status" jdbcType="BIT" javaType="java.lang.Boolean" />
      <arg column="sort_order" jdbcType="INTEGER" javaType="java.lang.Integer" />
      <arg column="create_time" jdbcType="TIMESTAMP" javaType="java.util.Date" />
      <arg column="update_time" jdbcType="TIMESTAMP" javaType="java.util.Date" />
    </constructor>
  </resultMap>
  <sql id="Base_Column_List" >
    id, parent_id, name, status, sort_order, create_time, update_time
  </sql>
  <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Integer" >
    select 
    <include refid="Base_Column_List" />
    from mmall_category
    where id = #{id,jdbcType=INTEGER}
  </select>
  <delete id="deleteByPrimaryKey" parameterType="java.lang.Integer" >
    delete from mmall_category
    where id = #{id,jdbcType=INTEGER}
  </delete>
  <insert id="insert" parameterType="com.hcxmall.pojo.Category" >
    insert into mmall_category (id, parent_id, name, 
      status, sort_order, create_time, 
      update_time)
    values (#{id,jdbcType=INTEGER}, #{parentId,jdbcType=INTEGER}, #{name,jdbcType=VARCHAR}, 
      #{status,jdbcType=BIT}, #{sortOrder,jdbcType=INTEGER},now(),
      now())
  </insert>
  <insert id="insertSelective" parameterType="com.hcxmall.pojo.Category" >
    insert into mmall_category
    <trim prefix="(" suffix=")" suffixOverrides="," >
      <if test="id != null" >
        id,
      </if>
      <if test="parentId != null" >
        parent_id,
      </if>
      <if test="name != null" >
        name,
      </if>
      <if test="status != null" >
        status,
      </if>
      <if test="sortOrder != null" >
        sort_order,
      </if>
      <if test="createTime != null" >
        create_time,
      </if>
      <if test="updateTime != null" >
        update_time,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides="," >
      <if test="id != null" >
        #{id,jdbcType=INTEGER},
      </if>
      <if test="parentId != null" >
        #{parentId,jdbcType=INTEGER},
      </if>
      <if test="name != null" >
        #{name,jdbcType=VARCHAR},
      </if>
      <if test="status != null" >
        #{status,jdbcType=BIT},
      </if>
      <if test="sortOrder != null" >
        #{sortOrder,jdbcType=INTEGER},
      </if>
      <if test="createTime != null" >
        now(),
      </if>
      <if test="updateTime != null" >
        now(),
      </if>
    </trim>
  </insert>
  <update id="updateByPrimaryKeySelective" parameterType="com.hcxmall.pojo.Category" >
    update mmall_category
    <set >
      <if test="parentId != null" >
        parent_id = #{parentId,jdbcType=INTEGER},
      </if>
      <if test="name != null" >
        name = #{name,jdbcType=VARCHAR},
      </if>
      <if test="status != null" >
        status = #{status,jdbcType=BIT},
      </if>
      <if test="sortOrder != null" >
        sort_order = #{sortOrder,jdbcType=INTEGER},
      </if>
      <if test="createTime != null" >
        create_time = #{createTime,jdbcType=TIMESTAMP},
      </if>
      <if test="updateTime != null" >
        update_time = now(),
      </if>
    </set>
    where id = #{id,jdbcType=INTEGER}
  </update>
  <update id="updateByPrimaryKey" parameterType="com.hcxmall.pojo.Category" >
    update mmall_category
    set parent_id = #{parentId,jdbcType=INTEGER},
      name = #{name,jdbcType=VARCHAR},
      status = #{status,jdbcType=BIT},
      sort_order = #{sortOrder,jdbcType=INTEGER},
      create_time = #{createTime,jdbcType=TIMESTAMP},
      update_time = now()
    where id = #{id,jdbcType=INTEGER}
  </update>

  <select id="selectCategoryChildrenParentId" resultMap="BaseResultMap" parameterType="int">
    SELECT <include refid="Base_Column_List"/>
    FROM mmall_category
    WHERE parent_id = #{parentId}
  </select>
</mapper>