java无限级分类的递归与循环
数据
表
CREATE TABLE `sys_dict` (
`id` bigint(20) NOT NULL AUTO_INCREMENT,
`parent_id` bigint(20) DEFAULT NULL COMMENT '父ID',
`name` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT NULL COMMENT '字典名称',
`code` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT NULL COMMENT '字典编码',
`val` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT NULL COMMENT '字典键值',
`sort` int(11) DEFAULT NULL COMMENT '字典排序',
`create_time` datetime(0) DEFAULT NULL COMMENT '创建时间',
`update_time` datetime(0) DEFAULT NULL COMMENT '最后更新时间',
`remarks` varchar(250) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT NULL COMMENT '备注',
PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 5 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci COMMENT = '字典表' ROW_FORMAT = Dynamic;
数据
INSERT INTO `sys_dict` VALUES (1, 0, '博客类型', 'blog_push_type', NULL, 1, '2019-04-15 02:33:48', '2019-04-15 02:33:48', NULL);
INSERT INTO `sys_dict` VALUES (2, 1, '原创', 'blog_push_original', '0', 1, '2019-04-15 02:33:48', '2019-04-15 02:33:48', NULL);
INSERT INTO `sys_dict` VALUES (3, 2, '转载', 'blog_push_reprint', '1', 2, '2019-04-15 02:33:48', '2019-04-15 02:33:48', NULL);
INSERT INTO `sys_dict` VALUES (4, 3, '翻译', 'blog_push_translate', '2', 3, '2019-04-15 02:33:48', '2019-04-15 02:33:48', NULL);
实体类
package com.laolang.km.modules.admin.entity;
import com.alibaba.fastjson.annotation.JSONField;
import java.util.Date;
/**
* 系统字典
* @author laolang
* @version 1.0
* 2019/4/13 12:29
*/
public class SysDictEntity {
@JSONField(ordinal = 1)
private Long id;
@JSONField(ordinal = 2)
private Long parentId;
@JSONField(ordinal = 3)
private String name;
@JSONField(ordinal = 4)
private String code;
@JSONField(ordinal = 5)
private String val;
@JSONField(ordinal = 6)
private Integer sort;
@JSONField(ordinal = 7,format = "yyyy-MM-dd HH:mm:ss")
private Date createTime;
@JSONField(ordinal = 8,format = "yyyy-MM-dd HH:mm:ss")
private Date updateTime;
@JSONField(deserialize = false,serialize = false)
private String remarks;
public SysDictEntity() {
}
}
vo
package com.laolang.km.modules.admin.vo;
import com.alibaba.fastjson.annotation.JSONField;
import com.laolang.km.modules.admin.entity.SysDictEntity;
import org.springframework.beans.BeanUtils;
import java.util.Date;
import java.util.List;
/**
* 字典 ztree
*
* @author laolang
* @version 1.0
* 2019/4/15 2:08
*/
public class SysDictTreeVo {
@JSONField(ordinal = 1)
private Long id;
@JSONField(ordinal = 2)
private Long parentId;
@JSONField(ordinal = 3)
private String name;
@JSONField(ordinal = 4)
private String code;
@JSONField(ordinal = 5)
private String val;
@JSONField(ordinal = 6)
private Integer sort;
@JSONField(ordinal = 7,format = "yyyy-MM-dd HH:mm:ss")
private Date createTime;
@JSONField(ordinal = 8,format = "yyyy-MM-dd HH:mm:ss")
private Date updateTime;
@JSONField(ordinal = 9)
private List<SysDictTreeVo> children;
public SysDictTreeVo() {
}
public static SysDictTreeVo entityToVo(SysDictEntity entity){
SysDictTreeVo vo = new SysDictTreeVo();
BeanUtils.copyProperties(entity,vo,"remarks");
return vo;
}
}
递归
public List<SysDictTreeVo> getTree(){
List<SysDictTreeVo> vos = new ArrayList<>();
buildTreeData(vos,0L);
return vos;
}
private boolean buildTreeData(List<SysDictTreeVo> root, Long parentId) {
List<SysDictEntity> entities = listByParentId(parentId);
if (entities.size() > 0 ){
for (SysDictEntity entity : entities) {
SysDictTreeVo vo = SysDictTreeVo.entityToVo(entity);
List<SysDictTreeVo> children = new ArrayList<>();
if( buildTreeData(children,entity.getId())){
vo.setChildren(children);
}else{
vo.setChildren(null);
}
root.add(vo);
}
return true;
}
return false;
}
循环
参考：https://www.jianshu.com/p/c7d6f9a9f42d
/**
* 循环获取字典数据 树
* 子ID必须小于父ID
* 查询所有数据时必须按照ID从小到大排序
*
* @return
*/
public List<SysDictTreeVo> getTreeData() {
// 查询所有字典数据
List<SysDictEntity> entities = listAll();
// 转化为vo
List<SysDictTreeVo> dictVos = new ArrayList<>();
entities.forEach(entity -> dictVos.add(SysDictTreeVo.entityToVo(entity)));
// 最终输出的树
List<SysDictTreeVo> vos = new ArrayList<>();
// 以ID为键保存每一条数据
Map<Long, SysDictTreeVo> map = new HashMap<>();
for (SysDictTreeVo dictVo : dictVos) {
long pid = dictVo.getParentId();
map.put(dictVo.getId(), dictVo);
// 如果在map不存在当前数据的父ID为键的数据，则pid为0，保存在输出树中
if (null == map.get(pid)) {
vos.add(dictVo);
} else {
// 如果在map存在当前数据的父ID为键的数据，则将当前数据加入到父节点的children中
SysDictTreeVo vo = map.get(pid);
if (null == vo.getChildren()) {
vo.setChildren(new ArrayList<>());
}
vo.getChildren().add(dictVo);
}
}
return vos;
}
另一种方式
实体类
package com.laolang.shopboot.business.catalog.entity;
import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import com.baomidou.mybatisplus.annotation.Version;
import io.swagger.annotations.ApiModel;
import io.swagger.annotations.ApiModelProperty;
import lombok.Data;
import lombok.experimental.Accessors;
import java.util.Date;
@ApiModel("catalog - 商品分类")
@TableName("catalog_product_cate")
@Accessors(chain = true)
@Data
public class ProductCate {
@TableId(value = "id", type = IdType.INPUT)
@ApiModelProperty(value = "id")
private Long id;
@ApiModelProperty(value = "分类名称")
private String name;
@ApiModelProperty(value = "父id")
private Long parentId;
@ApiModelProperty(value = "排序")
private Integer sort;
@ApiModelProperty(value = "createTime")
private Date createTime;
@ApiModelProperty(value = "updateTime")
private Date updateTime;
@Version
@ApiModelProperty(value = "version", hidden = true)
private Integer version;
}
实现过程
@Override
public List<ProductCateTreeVo> tree() {
// 查出所有
List<ProductCate> entityList = productCateService.list();
if (CollUtil.isEmpty(entityList)) {
return new ArrayList<>();
}
ProductCateMapStructMapper productCateMapStructMapper = getProductCateMapStructMapper();
// 根分类
List<ProductCateTreeVo> tree = entityList.stream()
.filter(entity -> 0L == entity.getParentId())
.map(productCateMapStructMapper::entity2treeVo)
.collect(Collectors.toList());
// 分类树map缓存
Map<Long, ProductCateTreeVo> treeMap = tree.stream().collect(Collectors.toMap(ProductCateTreeVo::getId, t -> t));
// 非根分类按照paretnId和sort排序
List<ProductCate> cateNotRootList = entityList.stream()
.filter(t -> 0L != t.getParentId())
.sorted(Comparator.comparing(ProductCate::getParentId).thenComparing(ProductCate::getSort))
.collect(Collectors.toList());
// 非根分类添加到树中
if (CollUtil.isNotEmpty(cateNotRootList)) {
cateNotRootList.forEach(node -> {
ProductCateTreeVo parent = treeMap.get(node.getParentId());
if (null != parent) {
if (CollUtil.isEmpty(parent.getChildren())) {
parent.setChildren(new ArrayList<>());
}
ProductCateTreeVo treeNode = productCateMapStructMapper.entity2treeVo(node);
parent.getChildren().add(treeNode);
treeMap.put(treeNode.getId(), treeNode);
}
});
}
return tree;
}