mybatis 中不同条件下排序方式

<if test="orderBy != null">
		order by
		<choose>
			<when test='orderBy=="age"'>age</when>
			<when test='orderBy=="size"'>size</when>
			<when test='orderBy=="price"'>price</when>
			<otherwise>
				${orderBy}
			</otherwise>
		</choose>
	</if>