mybatis的关联：自关联、一对一、一对多、多对多

一：自关联，如菜单表的自己跟自己关联

实体类：

public class Menu {

private String menuid;

private String menuname;

private String url;

private String icon;

}

包装类：

public class MenuVo {

private String menuid;

private String menuname;

private String url;

private String icon;

private List<Menu> menus;//下级菜单

}

映射文件： 其中menuid是父id，pid是子id

<resultMap type="com.ninemax.ssm.po.MenuVo" id="menusMap">

<id column="menuid" property="menuid" jdbcType="VARCHAR" />

<result column="menuname" property="menuname" jdbcType="VARCHAR" />

<result column="url" property="url" jdbcType="VARCHAR" />

<result column="icon" property="icon" jdbcType="VARCHAR" />

<collection property="menus" column="menuid" select="getMenus" />

</resultMap>

<select id="queryMenus" parameterType="string" resultMap="menusMap">

select * from menu where menuid = #{menuid,jdbcType=VARCHAR}

</select>

<select id="getMenus" parameterType="string" resultMap="menusMap">

select * from menu where pid = #{menuid}

</select>

二：一对一关联