原因有时实体类属性不够用，又不想写自定义VO了，所以用map，这样直接返回前台用起来也很方便

1 mapper.xml

注意是resultType 不是resultMap 否则报错

<select id="getOrder" parameterType="hashMap" resultType="java.util.Map">
    SELECT * FROM  order 
    <where>  
	<if test="orderId != null  and orderId != ''"> and order_id = #{orderId}</if>          
    </where>
</select>

2 mapper.java

List<Map<String, Object>> getOrder(Map<String,Object> map);

3 service 组装查询条件

public List<Map<String, Object>> getOrder(String storeId) {
    Map<String,Object> map=new HashMap<String,Object>();
    map.put("orderId",orderId);
    return storeApiOrderMapper.getOrder(map);
}