关于mybaits单入参报错问题

当传入数据只有一个时mybatis中<if>判断会出现There is no getter for property named 'subjectId' in 'class java.lang.Integer

用"_parameter"代替当前参数
正确：

<select id="selectSubjectByPId" parameterType="java.lang.Integer" resultType="java.util.Map"> 
select subjectId,
subjectName 
from ts_subject 
where subjectParentId= 0 
<if test="_parameter != null">
 and subjectId = #{_parameter,jdbcType=INTEGER} 
</if>
</select>

错误：

<select id="selectSubjectByPId" parameterType="java.lang.Integer" resultType="java.util.Map"> 
select subjectId,
subjectName 
from ts_subject 
where subjectParentId= 0 
<if test="subjectId != null"> 
and subjectId = #{subjectId,jdbcType=INTEGER} 
</if>
</select>

这时候就会出现异常.
There is no getter for property named 'subjectId' in 'class java.lang.Intege