mybatis常见错误

1、传入单个参数为list时

List<Objects> query(@param("list") List<String> list)

<select id="query" parameterType="java.util.List"  reasultMap="">

  <if test = " list != null and list.size() > 0">
       <foreach collection="list" item = "item" open="(" close = ")"
 separator = ",">
           #{item}
      </foreach>
  </if>

</select>

当判断一个集合不为空时需要用list.size() > 0 而不是 list ！= ‘’ 否则会出现参数异常，arraylist无法转换成String的错误