Mybatis报错—— A query was run and no Result Maps were found for the Mapped Statement

Mybatis报错—— A query was run and no Result Maps were found for the Mapped Statement 。。。 It’s likely that neither a Result Type nor a Result Map was specified.

报错如下

org.apache.ibatis.exceptions.PersistenceException: ### Error querying database.  Cause: org.apache.ibatis.executor.ExecutorException: A query was run and no Result Maps were found for the Mapped Statement 'com.mapper.EmployeeMapper.getEmpByIdAndLastname'.  It's likely that neither a Result Type nor a Result Map was specified.### The error may exist in com/mapper/EmployeeMapper.xml### The error may involve com.mapper.EmployeeMapper.getEmpByIdAndLastname### The error occurred while handling results### SQL: select * from tbl_employee where id = ? and last_name=?### Cause: org.apache.ibatis.executor.ExecutorException: A query was run and no Result Maps were found for the Mapped Statement 'com.mapper.EmployeeMapper.getEmpByIdAndLastname'.  It's likely that neither a Result Type nor a Result Map was specified.    at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)    ... 29 more

异常分析：
关键在第一段提示： It’s likely that neither a Result Type nor a Result Map was specified.意思是无法确定返回值类型。
如下代码：

<select id="getEmpById" >    select * from tbl_employee where id = #{id}</select>

在写select查询标签是，没加resultType属性。

异常解决，代码如下：

<select id="getEmpById" resultType="com.bean.Employee" >    select * from tbl_employee where id = #{id}</select>

小结：
在写select查询标签进行查询时，必须写resultType属性，不然mybatis无法确定返回值类型，就会报错。

补充：
1.进行查询时，resultType（返回值类型）属性不能省略。
2.进行增删改时，parameterType（参数类型）属性可以省略，且它们没有resultType属性，返回值可以直接在Mapper接口上定义。

mybatis允许增删改查直接定义以下类型返回值（Mapper接口中定义）
Integer（返回SQL语句影响的行数）、
Long（同上）
Boolean（返回SQL语句是否执行成功）

<!-- parameterType：参数类型，可以省略  --><insert id="addEmp" parameterType="com.bean.Employee">    INSERT INTO tbl_employee     VALUES (#{lastName}, #{gender},#{email});   </insert>