表结构如下:
CREATE TABLE `tree` (
`id` int NOT NULL,
`parent_id` int DEFAULT NULL,
`name` varchar(100) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;
INSERT INTO tree values (1,0,'一级目录-1');
INSERT INTO tree values (2,1,'二级目录-1');
INSERT INTO tree values (3,1,'二级目录-1');
INSERT INTO tree values (4,1,'二级目录-1');
INSERT INTO tree values (5,2,'二级目录-2');
INSERT INTO tree values (6,2,'二级目录-2');
INSERT INTO tree values (7,2,'二级目录-2');
工具类如下：
package cn.beichenhpy.util;
import cn.beichenhpy.enums.SqlConstant;
import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import lombok.Data;
import org.springframework.beans.factory.annotation.Autowired;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.stream.Collectors;
/**
* @author beichenhpy
* @version 1.0.0
* @apiNote M mapper T 为Tree的子类 用于查询树状层级结构
* <br>重要：1. 数据库对应的parentId 和 id 需要为int类型 2. 层数为从上到下
* <br> 不足：需要手动配置bean，不然统一配置会无法注入泛型
* @see Tree 树数据结构
* @since 2021/7/24 12:53
*/
public class TreeHelper<T extends TreeHelper.Tree, M extends BaseMapper<T>> {
@Autowired
M mapper;
//为内存计算使用，查询出来的所有树信息,线程安全
private volatile List<T> allRows;
/**
* 双检锁赋值
*/
public void init() {
if (allRows == null) {
synchronized (TreeHelper.class) {
if (allRows == null) {
allRows = new CopyOnWriteArrayList<>(mapper.selectList(null));
}
}
}
}
/**
* 通过api新增层级时调用，刷新成员变量AllRows
*/
public void updateCache() {
init();
}
/**
* 缺省的方法查询树形结构 默认使用一次加载到内存
*
* @param floor 层数 从上到下
* @return 返回树形结构
*/
public List<T> getTree(Integer floor) {
if (floor <= 0) {
throw new IllegalArgumentException("floor must > 0");
}
int parentId = floor - 1;
init();
//重置当前层数
return getChildren(parentId);
}
/**
* @param parentId 父极目录id
* @return 整个树
*/
private List<T> getChildren(Integer parentId) {
List<T> trees;
int floor = parentId;
trees = allRows.stream()
.filter(t -> parentId.equals(t.getParentId()))
.collect(Collectors.toList());
if (!trees.isEmpty()) {
floor++;
for (T tree : trees) {
tree.setCurrentFloorNum(floor);
//递归查询，直到return null结束
tree.setChildren(getChildren(tree.getId()));
}
return trees;
}
//未查询到结束递归
return null;
}
/**
* @author beichenhpy
* @version 1.0.0
* @apiNote 树及结构 子类可进行扩充
* @since 2021/7/24 12:57
*/
@Data
public static class Tree {
@TableId(type = IdType.AUTO)
private Integer id;
private Integer parentId;
/**
* 当前目录层级
*/
@TableField(exist = false)
private Integer currentFloorNum;
/**
* 叶子节点，（下一级）
*/
@TableField(exist = false)
private List<? extends TreeHelper.Tree> children;
}
/**
* 无缓存方式
*/
public static class TreeHelperNoCache {
/**
* 缺省的方法查询树形结构 默认使用一次加载到内存
*
* @param floor 层数 从上到下
* @return 返回树形结构
*/
public static <T extends TreeHelper.Tree, M extends BaseMapper<T>> List<T> getTree(Integer floor, M mapper) {
if (floor <= 0) {
throw new IllegalArgumentException("floor must > 0");
}
int parentId = floor - 1;
//重置当前层数
return getChildren(parentId, mapper.selectList(new QueryWrapper<T>().ge(SqlConstant.PARENT_ID.getValue(), parentId)));
}
/**
* @param parentId 父极目录id
* @return 整个树
*/
private static <T extends TreeHelper.Tree> List<T> getChildren(Integer parentId, List<T> rows) {
List<T> trees;
int floor = parentId;
trees = rows.stream()
.filter(t -> parentId.equals(t.getParentId()))
.collect(Collectors.toList());
if (!trees.isEmpty()) {
floor++;
for (T tree : trees) {
tree.setCurrentFloorNum(floor);
//递归查询，直到return null结束
tree.setChildren(getChildren(tree.getId(), rows));
}
return trees;
}
//未查询到结束递归
return null;
}
}
}
使用方式
- 无缓存，提供静态方式
新建一个子类继承于TreeHelper.Tree
TreeHelper
package cn.beichenhpy.modal;
import cn.beichenhpy.util.TreeHelper;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.*;
/**
* @author beichenhpy
* @version 1.0.0
* @apiNote
* @since 2021/7/24 13:43
*/
@ToString(callSuper = true)
@EqualsAndHashCode(callSuper = true)
@TableName("tree")
@Data
public class TreeInfo extends TreeHelper.Tree{
private String name;
}
Controller
package cn.beichenhpy.controller;
import cn.beichenhpy.mapper.TreeMapper;
import cn.beichenhpy.modal.TreeInfo;
import cn.beichenhpy.util.TreeHelper;
import lombok.AllArgsConstructor;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.List;
@AllArgsConstructor
@RestController
@RequestMapping("/api/v1")
public class ConsumerController {
private final TreeMapper treeMapper;
@GetMapping("/tree")
public List<TreeInfo> getTree(){
// 无缓存
return TreeHelper.TreeHelperNoCache.getTree(treeMapper,1);
}
}
- 有缓存，需要注册bean
注册bean
@Bean
public TreeHelper<TreeInfo, TreeMapper> treeHelper(){
return new TreeHelper<>();
}
Test
@Autowired
TreeHelper<TreeInfo,TreeMapper> treeHelper;
@Autowired
TreeMapper treeMapper;
@Test
public void test(){
long start1 = System.currentTimeMillis();
List<TreeInfo> tree2 = treeHelper.getTree(3);
long end1 = System.currentTimeMillis() - start1;
log.info("me:cost:{}",end1);
log.info("result:me:{}",tree2);
long start = System.currentTimeMillis();
List<TreeInfo> tree = treeHelper.getTree(3);
long end = System.currentTimeMillis() - start;
log.info("me:cost:{}",end);
log.info("result:me:{}",tree);
}
