【mmall】递归查询子节点并排重

代码

@Override
public ServerResponse getSelfAndChildrenCategory(Integer categoryId) {
    if (categoryId != null) return ServerResponse.error(ResponseCode.ILLEGAL_ARGUMENT.getCode(), "参数错误");
    Set<Category> categorySet = Sets.newHashSet(); // 初始化Set
    findChildCategory(categorySet, categoryId); // 递归
    List<Integer> categoryIdList = Lists.newArrayList(); // 初始化List
    for (Category categoryItem : categorySet) {
        categoryIdList.add(categoryItem.getId());
    }
    return ServerResponse.success(categoryIdList);
}

//递归算法,算出子节点
private Set<Category> findChildCategory(Set<Category> categorySet, Integer categoryId) {
    Category category = categoryMapper.selectByPrimaryKey(categoryId);
    // 将自己添加进去
    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.getChildrenCategory(categoryId);
    for (Category categoryItem : categoryList) {
        findChildCategory(categorySet, categoryItem.getId());
    }
    return categorySet;
}

/** 重写id的equals和hashCode方法,保证Set集合取出的值是不重复的 */
@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.equals(category.id);
}

@Override
public int hashCode() {
    return id.hashCode();
}

参考文章

使用Set集合时：重写equals的同时为什么必须重写hashcode