There is no getter for property named ‘expertGoodAtId’ in ‘class java.lang.Long’详解编程语言

问题：用mybatis查询时传入一个Long参数且进行判断时报:There is no getter for property named ‘expertGoodAtId’ in ‘class java.lang.Long’

原始xml文件：

<pre name="code" class="html"><!-- App专家接口查询：根据搜索条件查询，按专家id分组，按专家分数倒叙排序 --> 
	<select id="expertByScoreOrderQuery"  parameterType="java.lang.Long" resultType="java.util.Map"> 
		select ex.id,ex.expert_name AS expertName,ex.phone,ex.header_url AS headerUrl,ex.longitude,ex.latitude,ee.score, 
                GROUP_CONCAT(vm.models_name)AS expertGoodAt 
		from ykat_expert ex 
		LEFT JOIN ykat_expert_evaluate ee ON ex.id=ee.expert_id 
		LEFT JOIN ykat_expert_models em ON ee.expert_id=em.expert_id 
		LEFT JOIN ykat_vehicle_models vm ON em.vehicle_models_id=vm.id 
		where 1=1 and ex.is_del=1 
		<if test="expertGoodAtId!=null and expertGoodAtId!='' "> 
			and vm.id=#{expertGoodAtId} 
		</if> 
		GROUP BY ex.id 
		ORDER BY ee.score desc 
	</select>

解决方法：

方法一：无论什么参数均使用“_parameter”

<!-- App专家接口查询：根据搜索条件查询，按专家id分组，按专家分数倒叙排序 --> 
	<select id="expertByScoreOrderQuery"  parameterType="java.lang.Long" resultType="java.util.Map"> 
		select ex.id,ex.expert_name AS expertName,ex.phone,ex.header_url AS headerUrl,ex.longitude,ex.latitude,ee.score, 
                GROUP_CONCAT(vm.models_name)AS expertGoodAt 
		from ykat_expert ex 
		LEFT JOIN ykat_expert_evaluate ee ON ex.id=ee.expert_id 
		LEFT JOIN ykat_expert_models em ON ee.expert_id=em.expert_id 
		LEFT JOIN ykat_vehicle_models vm ON em.vehicle_models_id=vm.id 
		where 1=1 and ex.is_del=1 
		<if test="_parameter!=null and _parameter!='' "> 
			and vm.id=#{expertGoodAtId} 
		</if> 
		GROUP BY ex.id 
		ORDER BY ee.score desc 
	</select>

方法二：dao接口参数添加注释，说明是对应哪个参数名（实际开发中常用方法）

     /** 
     * @descript:App查询专家：根据查询条件，按专家分数倒叙排序 
     * @param expertGoodAtId 专家擅长车辆id 
     * @return 
     */ 
     List<Map<String, Object>> expertByScoreOrderQuery(@Param(value="expertGoodAtId")Long expertGoodAtId);

原因分析

Mybatis默认采用ONGL解析参数，所以会自动采用对象树的形式取long.num值引起报错

备注：

1：[email protected](“expertGoodAtId”)与@Param(value=”expertGoodAtId”)是一个意思

2： GROUP_CONCAT(vm.models_name)是mysql对查询2条相同数据合并成一行显示，并且必须根据某个字段分组，统计时使用distinct排除重复数据