Mybatis自查询递归查找子菜单

之前写过 java从数据库读取菜单，递归生成菜单树

今天才发现mybatis也可以递归查询子菜单

先看一下数据库

主键id，名称name，父id，和url

设计菜单类

public class Menu {    // 菜单id    private String id;    // 父菜单id    private String parentId;    // 菜单名称    private String name;    // 菜单url    private String url;    // 子菜单    private List<Menu> children;    // 省去getter setter和toString方法}

menuDao

public interface MenuDao {    /**     * 递归查找所有     *      * @return     */    public List<Menu> findAllRecursion();}

mapper.xml

    <resultMap type="Menu" id="recursionMenuMap">        <id column="id" property="id"/>        <result column="name" property="name"/>        <collection property="children" ofType="Menu" column="id" select="findMenuByParentId"/>    </resultMap>    <select id="findAllRecursion" resultMap="recursionMenuMap">        SELECT id,`name`,parent_id,url FROM menu WHERE parent_id ='' or parent_id is NULL ORDER BY `order` ASC    </select>    <select id="findMenuByParentId" resultType="Menu">        SELECT id,`name`,parent_id,url FROM menu WHERE parent_id = #{id} ORDER BY `order` ASC    </select>

其中findAllRecursion会查询到所有的父菜单，

因为我们定义的

<select id="findAllRecursion" resultMap="recursionMenuMap">

而在recursionMenuMap中我们定义了如何去查找子菜单，调用findMenuByParentId