传入的参数是String[] arr;

resultMap的值是resultMap的id,也是定义了java属性和表字段对应关系的配置的id

collection的值必须为array

item是指遍历时的别名,

index即下标

<!-- 使用数组为参数查出所有子代理商的订单 -->
	<select id="getOrderListByArray" resultMap="resultMap">
        select *
        from order_info o
        where o.ag_no in
        <foreach collection="array" item="item" index="index"
            open="(" close=")" separator=",">
            #{item}
        </foreach>
    </select>