获取树形结构的几种方式

获取树形结构的几种方式

一、存储过程实现
start with … connect by prior … 语句
示例

select connect_by_root(child_col) root, level ,
decode(connect_by_isleaf,0,'No',1,'Yes') is_leaf, sys_connect_by_path(child_col,'/') path
from tree
start with parent_col is null connect by prior child_col=parent_col

;
二、mybatis
xml文件实现(实际也是迭代的一种体现)

<resultMap type="com.test.mybatis.model.RoleInfo" id="roleModel">
<id column="id" property="roleid"/>
<result column="name" property="rolename"/>
<collection property="menulist" select="getMenu" column="id">
<!--当需要传递多个参数时使用{}-->
</collection>
</resultMap>

<select id="getRoleInfo" resultMap="roleModel">
select id,name from role
</select>
<select id="getMenu" resultType="com.test.mybatis.model.Menu">
select m.id,m.name
from menu m join roleandmenu ram on m.id=ram.menuId
where ram.roleId=#{id}
</select>

java 实体

import java.util.List;

@Data
public class RoleInfo {

private Integer roleid;
private String rolename;
private List<Menu> menulist;
}

三、迭代

1.先查出顶层，迭代查询子层

public List<TreeListDto> getInterfaceTree(List<TreeListDto> tldList, String interfaceId) {
List<TreeListDto> tlds = new ArrayList<TreeListDto>();
for (TreeListDto tld1 : tldList) {
if (MyStringUtil.isEquals(interfaceId, tld1.getParent())) {
String id = tld1.getKey();
List<TreeListDto> tmpTree = this.getInterfaceTree(tldList, id);
tld1.setChildren(tmpTree);
if (tmpTree.size() <= 0) {
tld1.setIsLeaf(true);
}
tlds.add(tld1);
}

}
return tlds;
}